6. NMFS - ALASKA FISHERIES SCIENCE CENTER
A. Agency Overview
Essentially all groundfish research at the Alaska Fisheries Science Center (AFSC) is conducted within the Resource Assessment and Conservation Engineering (RACE) Division, the Resource Ecology and Fisheries Management (REFM) Division, and the Auke Bay Laboratory (ABL). The RACE and REFM Divisions are divided along regional or disciplinary lines into a number of tasks and subtasks. A review of pertinent work by these tasks during the past year is presented below. A list of recent publications and reports produced by RACE, REFM, and ABL scientists are presented as Appendix I.
RACE DIVISION
In 1996 the primary activity of the RACE Division continued to be fishery-independent stock assessments of important groundfish species of the northeast Pacific Ocean and Bering Sea. Three bottom trawl surveys of groundfish resources were conducted in 1996 by RACE researchers in the Bering Sea, Gulf of Alaska, and West Coast. The Midwater Assessment and Conservation Engineering (MACE) Task conducted two acoustic surveys of pollock abundance in the Gulf of Alaska and Bering Sea in early 1997. Major emphasis in 1996 was in the Gulf of Alaska, in keeping with the triennial rotation of comprehensive surveys among three major geographic areas. The focus will be in the Aleutian Islands and Eastern Bering Sea regions in 1997. The Conservation Engineering group has also been refining methods used to stabilize research survey trawls, monitor the fishing configurations of sampling trawls, and explore possible methods of reducing bycatch. Underwater video and scanning sonar are being used to study the behavior of fish encountering trawl gear with the purpose of detecting behavior differences among species and size classes which might be exploited to reduce bycatch. The Recruitment Processes task conducted ten Fisheries-Oceanography Coordinated Investigations (FOCI) cruises in the spring of 1996, investigating the interaction between the environment and the spawning products of Gulf of Alaska and eastern Bering Sea pollock.
Claire Armistead transferred from the Bering Sea Groundfish Assessment team to the Crab Assessment Program at the Kodiak Laboratory. Jerry Hoff was hired to replace Armistead.
For more information on overall RACE Division programs, contact Division Director Dr. Gary Stauffer at (206)526-4170.
REFM DIVISION
The research and activities of the Resource Ecology and Fisheries Management Division (REFM) are designed to respond to the needs of the National Marine Fisheries Service regarding the conservation and management of fishery resources within the U.S. 200-mile Exclusive Economic Zone (EEZ) of the northeast Pacific Ocean and Bering Sea. Specifically, REFM's activities are organized under the Observer Program and the following tasks: Age and Growth Studies, Socioeconomic Assessments, and Status of Stocks and Multispecies Assessment. Scientists at AFSC assist in preparation of stock assessment documents for groundfish in the three management regions (Bering Sea/Aleutian Islands, Gulf of Alaska, and Washington-Oregon-California), conduct research to improve the precision of these assessments, and provide management support through membership in regional groundfish management teams.
For more information on overall REFM Division programs, contact Division Director Dr. Richard Marasco at (206)526-4172.
NMFS - AFSC - AUKE BAY LABORATORY
The Auke Bay Laboratory (ABL), located in Juneau, Alaska, is a major division of the NMFS Alaska Fisheries Science Center (AFSC). ABL's groundfish task (part of the laboratory's Marine Fishery Resources Program) is primarily involved with research and assessment of sablefish and rockfish in Alaska. Presently, the groundfish task is staffed by 10 permanent biologists. Two personnel changes that affected the task in 1996 were the transfer of Richard Haight to another task at ABL, and the inclusion of Lincoln Freese, formerly of ABL’s Habitat Program.
In 1996 field research, ABL's groundfish task conducted the annual NMFS sablefish longline survey in Alaska. Other field work by ABL included 1) participation in the 1996 triennial trawl survey of the Gulf of Alaska, 2) continued juvenile sablefish studies, and 3) a manned submersible study to determine effects of bottom trawling on the sea floor habitat.
Ongoing analytic activities involved management of ABL's sablefish tag database and preparation of three annual status of stocks documents for Gulf of Alaska groundfish: sablefish, slope rockfish, and pelagic shelf rockfish. Database analyses were conducted on Pacific ocean perch and northern rockfish, and on bycatch in rockfish trawl fisheries. Also, laboratory studies on rockfish genetics were completed.
For more information on overall Auke Bay Laboratory programs, contact Laboratory Director Dr. Michael Dahlberg at (907) 789-6001.
B. Multispecies Studies
1. Research
Bering Sea Crab/Groundfish Bottom Trawl Survey - RACE
The 1996 eastern Bering Sea crab-groundfish bottom trawl survey was conducted from June 5 to August 8, continuing the annual series of eastern Bering Sea resource assessment surveys which began in 1971. The primary purpose of the survey was to assess the abundance, distribution, and biological condition of the major demersal fish and crab resources on the eastern Bering Sea shelf. Further research conducted during the standard survey included: collection of stomachs from various groundfish for use in trophic interaction studies; additional sampling in areas of high king crab and Tanner crab abundance to reduce variability of population estimates; a continuing evaluation of potential bias in subsampling methods for large bottom trawl catches.
The survey encompassed an area approximately 465,000 km2 which included continental shelf waters from inner Bristol Bay, west to the 200 meter depth contour and from the Alaska
Peninsula, north to St. Matthew Island. The survey was conducted aboard two chartered fishing vessels. A total of 375 bottom trawl stations were sampled during the survey using the standard 83-112 eastern bottom trawl. This included an additional 20 stations sampled northwest of the standard area to better assess opilio tanner crab. Seawater temperature profiles and tow bottom depths were collected at most sampling sites using micro-bathythermographs (MBT) attached to the headrope of the net.
Estimates from the survey indicated little change in biomass compared to 1995 for almost all the flatfish species with some increase for arrowtooth flounder. Pacific cod estimates were slightly reduced from 1995 while walleye pollock decreased significantly for the demersal component of the stock.
For further information, contact Gary Walters, (206) 526-4143.
Gulf of Alaska Groundfish Bottom Trawl Survey - RACE
The fifth in a series of triennial groundfish surveys was conducted in the Gulf of Alaska (GOA) during the summer of 1996. This survey included the entire continental shelf and upper portion of the continental slope to 500 m depth. The survey objectives were to delineate the distributions of major groundfish and commercially important invertebrate species inhabiting the continental shelf and upper continental slope of the Gulf of Alaska in water depths to 500 m, collect data to estimate the abundance of the major groundfish species, collect data on specific biological parameters of general interest to researchers and resource managers (size, sex, and age composition, food habits, etc), collect accurate net mensuration data for all survey nets and vessels, and collect data for several collateral research projects.
The 1996 triennial survey used a stratified random sampling pattern consistent with previous triennial surveys. The Gulf of Alaska was divided into 49 strata categorized by water depth, type of geographical area (e.g., banks, gullies, and slopes) and INPFC statistical area boundaries. Prevailing rough bottom conditions in many areas require the use of rubber bobbin roller gear for all bottom trawling operations. The three charter vessels used for the survey towed a standard RACE Division poly-Nor'eastern high-opening bottom trawls rigged with rubber bobbin roller gear. Tow duration was reduced from the standard 30 minutes of past surveys to 15 minutes for this survey. Occasionally, tows of shorter duration were necessary to prevent net damage or when echosounder and Scanmar information suggested the potential for an exceptionally large catch.
Tows were attempted at a total of 868 stations (72% of the allocated stations), and 804 of these (93%) were successfully sampled and included in biomass and size composition analyses. Over the entire survey area, arrowtooth flounder was the most abundant groundfish encountered.. This species’s CPUE was the highest in three of the five INPFC areas covered by the survey and ranked second in CPUE in the other two areas. Pacific ocean perch, walleye pollock, Pacific halibut, and Pacific cod were also very important components of the Gulf-wide species composition. The species composition derived from the survey results is summarized below by INPFC area:
Shumagin INPFC area: Atka mackerel had the highest CPUE of any species, mostly due to one extremely large tow. Arrowtooth flounder, Pacific cod and walleye pollock were the next most abundant groundfish species and CPUEs were also high for Pacific halibut, Pacific ocean perch, and flathead sole.
Chirikof INPFC area: Arrowtooth flounder was the dominant species in survey catches with a mean CPUE that was the highest area-wide CPUE observed in the survey. Walleye pollock, Pacific ocean perch, Pacific halibut and Pacific cod were also important components of the species composition.
Kodiak INPFC area: Arrowtooth flounder and Pacific ocean perch were the two most abundant species. Pacific halibut, walleye pollock and Pacific cod also had notably high CPUEs.
Yakutat INPFC area: Arrowtooth flounder was the dominant species with a mean CPUE almost four times higher than the next most abundant species, Pacific ocean perch.
Southeastern INPFC area: Pacific ocean perch, arrowtooth flounder, sharpchin rockfish and walleye pollock predominated in the catches. Pacific ocean perch had a CPUE about 2.5 times the next highest CPUE (arrowtooth flounder).
For further information, contact Eric Brown, (206) 526-4157.
1996 West Coast Continental Slope Bottom Trawl Survey of Groundfish Resources - RACE
The RACE West Coast Groundfish Team conducted a bottom trawl survey of the groundfish resources of the upper continental slope (UCS) in the U.S. portion of the INPFC Vancouver and the INPFC Columbia (U.S./Canada border-43°00'N) management areas from October 15 to November 26, 1996. The survey, conducted aboard the NOAA ship MILLER FREEMAN, covered waters 183-1,280 m deep and continued a series of bottom trawl surveys begun in 1984 and conducted annually since 1988. Due to limited vessel time each year, slope groundfish trawl surveys have, in prior years, covered different but contiguous parts of the west coast UCS. Using this sampling strategy, it took until 1993 to obtain complete coverage of the west coast UCS north of San Francisco. Groundfish resources in the U.S.-Vancouver area UCS were last surveyed in 1992 and different sections of the Columbia area were surveyed in 1984, 1988,1989, 1992, and 1993. The survey period this year was increased from 4 to 6 weeks which, for the first time, enabled us to sample all possible stations in the Columbia area. With a similar amount of vessel time for the 1997 survey, we hope to complete another comprehensive set of west coast UCS survey data after only 3 years (1995-97).
The sampling design used for this survey was a cross between a systematic and random design. Sampling was conducted between 183 and 1,280 m in six strata of 183 m depth intervals (183-366, 367-549, 550-732, 733-914, 915-1,097, 1,098-1,280 m). There were 225 stations along 34 east-west tracklines spaced 16.7 km apart between lat 48°05'N near Nitinat Canyon and 43°00'N lat near Cape Blanco. We successfully sampled 203 of these. Spiny dogfish, Dover sole, and Pacific hake had the highest mean catch rates in the two shallowest strata and longspine thornyhead, Dover sole, true Tanner crab, sablefish, Pacific grenadier, and giant grenadier had the highest mean catch rates in the deepest 4 strata.
For the 1996 survey we continued using the improved gear and methodology adopted in 1995 and completed 250 trawls in the U.S. Vancouver and Columbia management areas. Three fishermen from Astoria, Oregon, also participated during the second leg of the cruise. They observed survey work in progress and were pleased with the performance of the reconfigured slope survey trawl and survey methods. Our work with the industry over the past three years led to the trawl modifications we adopted beginning with the 1995 survey. Our observations show that our modifications have vastly improved the stability of our sampling trawl. We have also adopted measures to standardize the manner the trawl is fished, which has improved our confidence in the data collected.
These surveys provide information to fisheries managers and the fishing industry on the abundance, distribution, and biological characteristics of groundfish resources of the northeastern Pacific Ocean upper continental slope between the US-Canada border and central California. West coast slope species for which there is a particular need of resource information for management purposes are sablefish, shortspine thornyhead, longspine thornyhead, Dover sole , and arrowtooth flounder. A complete set of analyses including descriptions of species’ distribution and estimates of their abundance (biomass and numbers), size, and age composition have been forwarded to authors developing stock assessments of these groundfish resources. Length-weight and length-maturity relationships have also been derived to assist managers in assessing the status of these important upper slope groundfish species.
For further information, contact Bob Lauth, (206) 526-4121.
Age and Growth Task - REFM
The Age and Growth Task of the REFM Division serves as the Alaska Fisheries Science Center's ageing unit for groundfish species. The task consists of a biometrician, age validation researcher, data manager/technician, and 8 age readers. Ages are usually determined from otoliths, but scales and/or finrays are sometimes used.
Data provided by the task are used in stock assessment work which contributes to the estimation of the allowable catch of many commercially important groundfish species. These species include walleye pollock, Pacific whiting, Pacific cod, sablefish, Pacific ocean perch, northern and dusky rockfishes, Atka mackerel, yellowfin sole, rock sole, rex sole, and misc. sole and rockfish species.
The radiometric lab of the Age Unit is continuing its ongoing study on the ageing of several rockfish species: Pacific ocean perch, shortspine thornyheads, shortrakers, rougheye, northern and dusky. Also ongoing is a study with the NMML to apply radiometric ageing to gray and bowhead whales. Some of the results from these studies have been puzzling and are currently being evaluated. The work involved is difficult and ground breaking, so problems are to be expected.
Delsa Anderl is also continuing working with Jon Heifetz on a study based on known age sablefish. As part of this study, edge growth increments are being measured on several hundred otoliths.
In closing, Julie Lyons, the senior age reader of the Age Unit will be retiring this summer following 32 years of service. The Age Unit often looked to Julie for her depth of knowledge and sense of humour when things got tough. Her kind and caring nature will be sorely missed.
For further information contact Dr. Daniel K. Kimura (206) 526-4200.
Resource Ecology and Ecosystem Modelling - REFM
(formerly Trophic Interactions Program)
Sample collection and analysis - The Resource Ecology and Ecosystem Modelling Task continued regular collection of food habits information on key fish predators in the North Pacific. Program personnel, fishery observers, and others collected fish stomachs for the group. About 6,978 stomachs were collected from the Bering Sea, 2,561 from the Gulf of Alaska/Aleutian Islands, and about 100 from the West coast region. Bering Sea species sampled were walleye pollock, Pacific cod, yellowfin sole, Alaska plaice, rock sole, flathead sole, skates, arrowtooth flounder, Greenland turbot and Pacific halibut. Gulf of Alaska/Aleutian Island species sampled included walleye pollock, Pacific cod, arrowtooth flounder, Pacific halibut, sablefish, Atka mackerel, and prowfish. Pacific hake stomachs were collected from the West coast region. Shipboard scans of fish stomach contents were performed on 269 fish (primarily walleye pollock) in the eastern Bering Sea. Laboratory analysis of stomach contents by region totalled 8796, 3425 and 1940 stomachs for the Bering Sea and Gulf of Alaska/Aleutian Islands, and West coast regions, respectively.
Ecological impacts - Ecological impacts of proposed improved retention and utilization options (IR/IU) for North Pacific groundfish currently under consideration by the North Pacific Fishery Management Council were assessed. Possible ecological impacts of IR/IU relative to the status quo would primarily occur through the decrease in the amounts of walleye pollock, Pacific cod, yellowfin sole and rock sole that are returned to the sea. The decrease in discards returned to the sea could result in a decrease in the amount of food available to scavengers and produce a decline in growth or reproductive output of species that rely on discards for a major portion of their food intake. Also, changes in energy flow to the detritus and local enrichment through an increase in processing waste (offal) could occur.
Data indicated that current levels of offal and discards are not a significant source of energy for these populations and the adoption of increased retention of walleye pollock, Pacific cod, and yellowfin sole would not cause a large decline in the amount of dead organic matter returned to the sea.
Model review - A review of models for predicting the effects of climate change on upper trophic level species was prepared and presented at a recent PICES Model workshop in Nemuro, Japan (Livingston, 1997). This review covered models that explicitly consider climate effects on fish, mammals, and birds in a mechanistic fashion. Models reviewed included early-life history, full-life cycle, and multispecies models.
Groundfish Food Habits on the Eastern Bering Sea Slope -
A report summarizing groundfish food habits in the eastern Bering Sea slope region was completed (Lang and Livingston, 1996). The focus of this study was to identify the trophic interactions of walleye pollock (Theragra chalcogramma), Pacific cod (Gadus macrocephalus), Greenland turbot (Reinhardtius hippoglossoides), arrowtooth flounder (Atheresthes stomias), and flathead sole (Hippoglossoides elassodon) in the slope region of the eastern Bering Sea. The general diet of each species is described and dietary variation due to predator size, depth, season, and latitude within the slope region were examined. In the slope region, mesopelagic fish species from the families Bathylagidae and Myctophidae were found, in addition to pollock, to be important forage fish of groundfish predators.
Trophic Relationships of Forage Fish - Trophic relationships of forage fish (Osmeridae, Myctophidae, Bathylagidae, Ammodytes spp., Pacific sandfish) were summarized as part of an environmental assessment for amending the Fishery Management Plans for the Groundfish of the Bering Sea/Aleutian Islands and Gulf of Alaska in order to create and manage a forage fish species category.
Trophic Role of Atka Mackerel in the Aleutian Islands - Atka mackerel, the most abundant groundfish species in the Aleutian Islands, plays an important role in the Aleutian Islands ecosystem. A report summarizing its role as predator and prey is currently being prepared. Atka mackerel is consumed by Pacific halibut, Pacific cod, and arrowtooth flounder in this region. Atka mackerel are also important food of the following marine mammals and seabirds: northern fur seal, northern sea lion, harbor seal, Dall's porpoise, thick-billed murre, horned puffin, and tufted puffin. As predators, Atka mackerel were mainly zooplankton eaters.
Ecosystem Research Overview - A two day overview of the Alaska Fisheries Science Center’s ecosystem-related research was organized to provide information to the North Pacific Fishery Management Council’s newly-formed Ecosystem Committee. The main focus was to provide an overview of Center programs such as RACE-FOCI, NMML- pinniped research, ABL/RACE habitat research, REFM-Resource Ecology and Ecosystem Modelling, and the incorporation of ecosystem-related research information into groundfish stock assessments. A review of the proposed framework for the description, identification, conservation, and enhancement of essential fish habitat was given by the NMFS Alaska Regional Office. An overview of various proposed/current ecosystem management schemes was given to promote discussion about the goals and directions of the NPFMC Ecosystem Committee. The result of the meeting was a better understanding of the types of ecosystem-related research being performed, current limitations in our knowledge, and prospects for the future.
For more information please contact Pat Livingston at (206)526-4242.
2. Stock Assessment
STATUS OF STOCKS AND MULTISPECIES ASSESSMENT TASK
The Status of Stocks and Multispecies Assessment Task (SSMA) is responsible for providing stock assessments and management advice for groundfish in the North Pacific Ocean and the Bering sea. In addition, Task members conduct research to improve the precision of these assessments, and provide technical support for the evaluation of potential impacts of proposed fishery management measures.
During the past year, the SSMA task prepared stock assessments for West Coast, Gulf of Alaska and Bering Sea/Aleutian Islands groundfish. These assessment documents were prepared for the groundfish management plan teams of the North Pacific Fishery Management Council and the Pacific Fishery Management Council.
Assessment scientists provided analytic assistance on many current fisheries management issues. These included: 1) identification and prioritization of research activities that may lead to improved groundfish stock assessessments 2) drafting guidelines for implementing the sustainable fisheries act; 3) assisted in identifying methods for defining and interperting essential fish habitat.
Research activities spanned a broad range of topics. Field studies initiated by task members included a pilot study to evaluate the utility of using acoustic methods for classifying bottom habitat. Several task members are actively investigating processes underlying the shifts in the distribution of groundfish stocks in the North Pacific and Bering Sea. Ongoing research activties include studies of risk assessment in stock assessments, ecosystem impacts of commercial harvest and methods for improving biomass estimates of fish that exhibit extremely patchy distributions (e.g. rockfish and Atka mackerel). Task members served on the organizing committee and presented oral presentations for an international symposium on Pacific hake. Task members served on international steering committes of U.S. GLOBEC, the North Pacific Marine Science Organization PICES and the Joint Russian U.S. Research Program .
For further information, contact Dr. Vidar Wespestad (206) 526-4249 or Dr. Anne Hollowed (206) 526-4223.
3. Management
North Pacific Groundfish Observer Program - REFM
The North Pacific Groundfish Observer Program is responsible for placement of observers on vessels fishing for groundfish species in the EEZ of the northeastern Pacific Ocean and Bering Sea. Observers collect data which provide the basis for in-season management of the groundfish fisheries by NMFS, provide a means for evaluating and developing management strategies by regional management councils and NMFS, and are used in the stock assessment process. Observers play important roles in providing information that is critical to the continuation of the U.S. fishing industry.
During 1996, no foreign vessels were allowed to catch or process fish in the U.S. EEZ along the west coast and Alaska. The Observer Program trained and deployed 540 observers to vessels fishing off Alaska, and 19 observers to vessels fishing off the Washington-Oregon-California coast. The Program was responsible for defining the sampling duties and data collection methods used by observers, training of the observers prior to deployment, debriefing of observers upon their return, and editing and managing the resulting data. The catch data were provided to the Alaska and Northwest Regional Offices to assist in management decisions regarding the catches of groundfish and prohibited species. Data were also collected regarding the operations of the groundfish fishery.
Throughout 1996, the Observer Program has continued to develop and change its information systems. One significant change involves the development of an electronic reporting system to transmit observer sampling data from sea, which was field-tested in early 1997. This system will increase efficiency and accuracy of data transmission by eliminating the need for observers to summarize, code and format their data into catch messages.
Fieldwork for a research project designed to evaluate Observer Program procedures for estimation of total catch weight was completed in March, 1997. The objectives of the research project are as follows:
For further information, contact Dr. William Karp, (206) 526-4194.
Socioeconomic Assessment Task - REFM
From May 1996 through April 1997, the Socioeconomic Assessment Task was actively involved in providing economic information used in the evaluation of management measures being considered by the Pacific and North Pacific Fishery Management Councils. Task members served on the BSAI, GOA, and West Coast groundfish plan teams and on both NPFMC and PFMC technical work groups and contributed significantly to, and in several cases had the lead for, the analyses and review of the following fishery management actions: (1) NPFMC increased retention and utilization program for the Alaska groundfish fisheries, (2) NPFMC individual vessel bycatch allowance program for the Alaska groundfish fisheries, (3) allocation of the BSAI Pacific cod TAC by user group, (4) the expansion of the community development quota (CDQ) program in the BSAI groundfish and crab fisheries, (5) allowing limited at-sea processing by catcher vessels in the Alaska groundfish fishery, (6) allocation of halibut between the commercial halibut fishery and the recreational charter boat fishery off Alaska, (7) groundfish and crab license limitation program off Alaska, (8) PFMC fixed gear sablefish fishery management, and (9) PFMC Pacific whiting allocation between on-shore and at-sea processors.
Task members prepared publications on the following topics: (1) the economics of bycatch, (2) the economic status of the Alaska groundfish fisheries, (3) the exports of edible fishery products from the Pacific Northwest and Alaska, (4) the IFQ program for the Alaska sablefish and halibut fisheries, (5) markets for access under extended jurisdictions, (6) fixed and joint cost allocation in assessing management alternatives, (7) multispecies management, (8) global fishery and trade policy, and (9) cooperative fishing arrangements in EEZs.
Task members provided economic advice and technical review and support for: (1) Saltonstall-Kennedy and Sea Grant research proposals, (2) the development of the AKFIN system, (3) the evaluation of the Alaska halibut and sablefish IFQ program, (4) university research proposals, (5) the economic counterpart to "Our Living Oceans", (6) a preliminary assessment of the effects of the PFMC limited entry program, (7) the development of ecological and economic valuation assessment techniques for resource management, (8) NMFS limited access workshops, (9) NMFS efforts to determine the feasibility of monitoring catch and bycatch of individual fishing vessels in support of future CDQ, ITQ, and VBA programs, (10) the OECD study of the economic aspects of the management of living marine resources, (11) the development of a NMFS bycatch plan, (12) the development of guidelines for new national standards and authority under the Magnuson-Stevens Act, (13) the development of a program to collect cost, earnings and employment data for PFMC and NPFMC fisheries, and (14) the NMFS implementation plan for the FAO Code of Conduct for Responsible Fisheries.
For further information contact Dr. Joe Terry (206) 526-4253, jterry@afsc.noaa.gov.
C. By species, by agency
1. Pacific cod
b. Stock Assessment
BERING SEA/ALEUTIANS
The length-based Synthesis model used in the previous three stock assessments was revised for the present assessment. The models used to assess the EBS and GOA stocks were brought into complete structural conformity with each other. The biomass projections from the revised model are very much in line with last year's projections, with projected 1997 biomass increasing by only 5% from the 1997 projection contained in last year’s SAFE report. The 1992 year class continues to look very strong, although it is projected to contribute less heavily to the fishery in the years following 1997.
Spawning biomass is projected to remain above B40% in 1997 (413,000 t versus 356,000 t). The ABC is based on F40% (=0.27) harvest strategy, which gives a projected 1997 catch of 306,000 t. Although this ABC value is almost identical to the current year’s ABC, it implies the possibility of a 1997 catch much greater than the current year’s catch, even though the stock is projected to decline. The Plan Team expressed a concern that the natural mortality rate assumed in the assessment (0.37) may be too high. However, the assessment chapter includes a risk analysis which indicates that the uncertainties associated with the assumed values of the natural mortality rate and survey catchability coefficient do not suggest that ABC for 1997 should be set at a lower value. However, the model projects significant decreases in ABC for the years following 1997.
The Plan Team’s OFL was determined from the tier 3 formula. Given that the stock is projected to remain above B40% for 1997, an F30% value of 0.38 gives a 1997 OFL of 418,000 t.
GULF OF ALASKA
The main issues addressed in the latest Pacific cod assessment include an evaluation of survey catchability and measures to make the model used on the Eastern Bering Sea (EBS) stock nearly identical to that used in the Gulf. This resulted in adding some simplifications to the Bering Sea model and some complexity to the Gulf model. The addition of data from the 1996 Gulf triennial survey suggested an increase in biomass over the 1993 estimate. Also, there is a preliminary indication that the 1995 year class may be above average. The long-term target biomass (B40%) for Pacific cod in the Gulf was estimated at about 147,000 mt of female spawners while the estimate for the beginning of 1997 is on the order of 207,000 mt. The Team considered the stock status to be in tier 3a.
The author provided a comprehensive analysis on the affect of uncertainty in the natural mortality rate and survey catchability. From these the author derived a risk-averse level of ABC levels. This analysis provided a decision theoretic perspective which is preferable to using ad-hoc methods (such as setting ABC to the value that corresponds to the lower 95% confidence bounds). The Groundfish Plan Team acknowleded that given the complicated technical aspects of the Gulf Pacific cod model, particularly in developing a realistic posterior probability density estimate, it may be difficult in future years to base ABC recommendations on a similar risk-averse strategy. The author was requested to pursue methods to simplify this task (e.g., using a "proxy" harvest rate with fixed values for natural mortality and survey catchability).
The F40% yield for 1997 would be 126,000 mt under tier 3a. However, given the risk-averse analysis as presented, the author’s recommendation was used to set ABC equal to 81,500 mt. The breakdown of ABC to Western, Central, and Eastern Gulf regions would be 28,500 mt, 51,400 mt, and 1,600 mt, respectively. The overfishing level of 180,000 mt is based on the F30% harvest guideline.
For further information, contact Dr. Grant Thompson at (206) 526-4232.
2. Shelf rockfish
b. Stock Assessment
GULF OF ALASKA
Pelagic Shelf Rockfish
The pelagic shelf rockfish assemblage is comprised of five species that inhabit waters of the continental shelf of the Gulf of Alaska and that are thought to exhibit midwater, schooling behavior. At certain times, however, some of these fish are caught in bottom trawls. Dusky rockfish appears to be the most abundant species in the group, and has been the target of a bottom trawl fishery since the late 1980's. A jig fishery for black rockfish has also existed in the Gulf of Alaska since 1991, mostly in the Central area. For several years, there has been concern that grouping these species into one assemblage may not be appropriate for their rational management. Dusky rockfish are mostly found on trawlable offshore banks, and past ABC’s for the assemblage have been derived almost entirely from biomass estimates of dusky rockfish in the triennial trawl surveys. Black rockfish, however, inhabit rough-bottom nearshore waters that are not sampled in the trawl surveys; thus, the ABC’s for the assemblage have not taken into account stock condition of black rockfish, which could result in over-harvest of this species in the jig fishery. As a possible solution to this problem, the Gulf of Alaska Groundfish Plan Team submitted a management plan amendment in 1995, which, as modified in 1996, would divide the pelagic shelf assemblage into two components: inshore, consisting of black and blue rockfish; and offshore, consisting of dusky, yellowtail, and widow rockfish. The Plan Team also recommended as a preferred alternative within the amendment that management authority of the inshore component be transferred to the State of Alaska.
Although the fate of the amendment has yet to be determined, the North Pacific Fishery Management Council decided to proceed with separating the assemblage in 1997 into inshore and offshore components in the Central area to prevent over-exploitation of black rockfish in this region. ABC in 1997 for pelagic shelf rockfish in the Western and Eastern areas of the Gulf, together with the assemblage’s offshore component in the Central area, is calculated using a procedure similar to that applied to the entire assemblage in previous years. Exploitable biomass for these three regions combined is based on the average of the biomasses estimated in the 1990, 1993, and 1996 triennial trawl surveys: 54,220 mt. Applying an F=M strategy to this biomass, in which the annual exploitation rate is set equal to the estimated rate of natural mortality for dusky rockfish (0.09), yields a Gulfwide ABC of 4,880 mt for 1997.
A different procedure is necessary to calculate ABC for the inshore component in the Central area, because no biomass estimates are available for black and blue rockfish. NPFMC guidelines stipulate that, when biomass estimates for a species are unavailable, ABC should be computed as 0.75 times the average annual commercial catch. The average commercial catch for black rockfish in the Central area over the years 1991-95 is estimated to be 357 mt. Hence, 1997 ABC for the inshore component there is 257 mt.
For more information, contact David Clausen at (907) 789-6049 or Jon Heifetz at (907) 789-6054.
3. Slope rockfish
a. Research
GULF OF ALASKA
Distribution and Maturity of Pacific Ocean Perch in the Gulf of Alaska
In cooperation with ABL, Chris Lunsford, a graduate student at the University of Alaska Fairbanks, Juneau Center, is studying the geographic distribution patterns of Pacific ocean perch in the Gulf of Alaska. Survey and commercial fishery observer catch data have been analyzed using the geographic information system (GIS) program ArcView. Comparisons in the distribution of catch have been made for the 1987, 1990, and 1993 triennial trawl surveys, and between these catches and those in the commercial fishery. Based on this analysis, alternative sampling designs have been examined to help improve survey biomass estimates of Pacific ocean perch in the Gulf of Alaska.
This study also includes work on the development of maturity schedules for female Pacific ocean perch in the Gulf of Alaska. Size and age at 50% maturity are being determined for the three management areas of the Gulf (Western, Central, and Eastern areas). Results so far indicate that length at 50% maturity is similar among areas, which suggests that age at 50% maturity may also be similar between areas. Age results have only been completed for the Eastern area, for which the age at 50% maturity was 10.5 years. These preliminary estimates have been incorporated into the stock synthesis model and are reflected in the calculations of ABC for Pacific ocean perch in 1997.
For more information, contact Jonathan Heifetz at (907) 789-6054.
Electrophoretic Studies of Rougheye Rockfish
ABL’s genetics task has completed allozyme analysis from 650 rougheye rockfish (Sebastes aleutianus) collected in the eastern Gulf of Alaska, Kodiak, and the Aleutian regions. The purpose of the study is to investigate the geographic stock structure of rougheye rockfish. Of the 47 enzymes screened, 23 were resolved for a total of 30 loci. Results show an apparent north-south geographic cline exists in southeastern Alaska waters. Significant heterogeneity was detected between the eastern Gulf of Alaska and the Aleutians- Kodiak region, which indicates rougheye rockfish in these two areas may be separate stocks. No heterogeneity was detected among sub-regions of the Aleutians, though sample sizes for these sub-regions were small.
For more information, contact Sharon Hawkins at (907) 789-6081.
Genetic Studies of Slope Rockfish
A cooperative study of rockfish genetics involving ABL and Dr. Anthony Gharrett and Andy Gray at the University of Alaska Fairbanks, Juneau Center, is nearing completion. The study is based on techniques of polymerase chain reaction (PCR) amplification of mitochondrial DNA (mtDNA). A. Gharrett and A. Gray are using genetic variation to study relationships among rockfish species, to identify larval and post-larval rockfish, and to examine population structure of rockfish species. Gharrett and Gray are using PCR to amplify regional mtDNA sequences and using restriction endonuclease digestions to detect sequence differences.
One facet of this study involved comparing rougheye rockfish samples from the eastern Gulf of Alaska and Aleutian regions. The results confirm observations from electrophoretic studies that genetic-based stock differences exist for rougheye rockfish between these two regions.
Another facet of the study nearing completeness is a comparison of mtDNA profiles from fourteen rockfish species collected in the Gulf of Alaska. All but two of the species can be identified using their mtDNA profiles, and the results have been applied to identification of larval rockfish captured in Chatham Strait, southeastern Alaska.
For more information, contact Anthony Gharrett at (907) 465-6445 or Jonathan Heifetz at (907) 789-6054.
Northern Rockfish Study
ABL is preparing a synopsis on northern rockfish (Sebastes polyspinis) that will provide information on its commercial fishery and biology in the Gulf of Alaska and Aleutian Islands. Although northern rockfish in recent years have become relatively valuable in Alaskan trawl fisheries, little is known about this species. The present study has used the AFSC trawl survey and commercial fishery observer databases to examine geographic patterns of distribution and other aspects of northern rockfish biology, such as age and growth. The preferred habitat for adults appears to be at about 100 m depth on shallow offshore banks of the outer continental shelf, such as Portlock Bank in the Gulf of Alaska and Petrel Bank in the Aleutian Islands. The age and growth data show significantly different growth rates between the Gulf of Alaska and the Aleutians. Aleutian fish grow much slower and attain a smaller maximum size, which suggests that fish in each region are separate populations.
For more information, contact David Clausen at (907) 789-6049.
Bycatch in Rockfish Fisheries of the Gulf of Alaska
Preliminary estimates of "natural" bycatch rates of commercially managed species that are caught in rockfish trawl fisheries of the Gulf of Alaska were provided in a report by ABL to the North Pacific Fishery Management Council. The natural bycatch rate is defined as the ratio of the incidental catch of a particular species or assemblage to the catch of another species or assemblage that is the target of a directed fishery. These estimates were determined by examining data in both the AFSC trawl survey and commercial fishery observer databases. The estimated rates will provide information to evaluate the appropriateness of current allowable catch percentages of species that are on "bycatch only" status during rockfish fisheries, and to aid in the in-season management of rockfish fisheries.
For more information contact, Jonathan Heifetz at (907) 789-6054.
b. Stock Assessment
BERING SEA
Pacific Ocean Perch
The POP complex consists of true POP (Sebastes alutus) and four other red rockfish species (northern rockfish, rougheye rockfish, sharpchin rockfish, and shortraker rockfish). Prior to 1991, the complex was managed as a unit in each of the two management areas. Since 1991, however, the Council has managed S. alutus separately from the other species in both areas, and has also split out rougheye and shortraker in the Aleutians. This was done to avoid excessive catches of the less abundant members of the complex, particularly shortraker and rougheye. Beginning in 1996, the ABC and TAC for true POP have been subdivided within the AI area, based on an average of the biomass estimates from the two most recent trawl surveys: Eastern subarea (541) 25%, Central subarea (542) 25%, and Western subarea (543) 50%.
The stock assessment for this complex is based mainly on S. alutus, which has the most data and is the most abundant species in the complex. An age-based Synthesis model has been used as the primary analytic tool for the last four assessments. The chapter authors note that some changes have occurred in biomass estimates for the eastern Bering Sea stock due to the correction of errors in catch data from certain years in the time series. Synthesis results indicate that the S. alutus stocks in both areas underwent declines in abundance during the 1960s and early 1970s, and remained low in abundance through the early 1980s. For several years, the Council set TAC well below (normally at 50% of) ABC to promote rebuilding of the stocks. Through a combination of these management actions and improved recruitment, the stocks have been recovering steadily.
The recommended ABC (2,800 t) was set by adjusting the F44% (=0.052) rate according to the relationship between projected 1997 spawning biomass and B40% , giving an FABC value of 0.049. The F44% rate was chosen over an F40% rate because a previous analysis of S. alutus in the Gulf of Alaska showed that the F44% rate produces the best harvest policy given the existing level uncertainty in the stock-recruitment relationship and the life-history characteristics of the species.
The Plan Team’s OFL was determined from the tier 3 formula. Using an F30% value of 0.085 and adjusting by the ratio of projected 1997 spawning biomass to B40%, the 1997 OFL is 5,400.
ALEUTIAN ISLANDS
The relatively rapid rebuilding of this stock during the l980s has resulted in a biomass level which appears substantially larger than that which would be expected in the long term under an F44% (=0.063) harvest strategy. Consequently, the ABC (16,400 t) that would be implied by application of an F44% harvest strategy would probably not be sustainable for long. In order to address uncertainty in the survey results and to estimate an ABC that would lead to more stable yields, the chapter authors estimated the long-term average catch corresponding to an F44% harvest strategy. It is recommended that this quantity (12,800 t) be used as ABC for the coming year. The fishing mortality rate implied by this approach may be approximated by the formula FABC = 0.063´12,800/16,400 = 0.049.
The Plan Team’s OFL was determined from the tier 3 formula. Using an F30% value of 0.10, and given that the stock is projected to remain above B40%, the 1997 OFL is 25,300.
For further information, contact Daniel Ito at (206) 526-4231.
GULF OF ALASKA
Slope rockfish are defined as those species of Sebastes that, as adults, inhabit waters of the continental slope, generally in depths greater than 150-200 m. Twenty-one species of rockfish are classified into the slope assemblage, the most abundant of which are Pacific ocean perch, and northern, rougheye, redstripe, sharpchin, shortraker, silvergrey, and harlequin rockfish. Until recently, the stock abundance of slope rockfish, especially Pacific ocean perch, was considered to be quite depressed compared to its former abundance in the early 1960's. The fifth triennial trawl survey of the Gulf of Alaska was completed in 1996, and it showed a substantial increase in biomass of Pacific ocean perch. This increase follows another large increase in biomass seen in the previous trawl survey in 1993, and suggests that current abundance of Pacific ocean perch is much improved in comparison with its formerly depressed condition. The "stock synthesis" model is applied to Pacific ocean perch. This model incorporates age composition, in addition to using other data such as fishery CPUE and estimated biomass from trawl surveys. Based on the model, our best estimate of exploitable biomass for Pacific ocean perch in the Gulf of Alaska is now 242,300 mt, up from the previous year’s estimate of 163,219 mt. Exploitable biomass for the other species in the assemblage is estimated from the average values in the 1990, 1993 and 1996 trawl surveys, and totals 252,460 mt. Unlike Pacific ocean perch, survey biomass estimates for the other species have generally not shown large increases in recent years.
Pacific ocean perch age samples indicate the presence of a strong 1986 year class, especially in the central and western Gulf of Alaska. This age class was first noted in samples from the 1990 triennial survey and verified in the 1993 survey. Past age samples have also identified a strong 1976 year class. Age composition from the 1996 survey has not been incorporated into the current assessment model.
To prevent possible over-exploitation of the more desirable species, the slope rockfish assemblage is divided into four subgroups: Pacific ocean perch, shortraker/rougheye rockfish, northern rockfish, and other slope rockfish. Separate ABC's are assigned to each subgroup. Pacific ocean perch are presently managed using an F40% strategy. The other subgroups are managed under an F=M strategy, in which the annual exploitation rate is set equal to the rate of natural mortality. The 1997 ABC's are as follows: Pacific ocean perch, 12,990 mt; shortraker/rougheye rockfish, 1,590 mt; northern rockfish, 5,000 mt, and other slope rockfish, 5,260 mt.
In 1993, a rebuilding plan was initiated for Pacific ocean perch. Under this plan, an F55% rate adjusted downward by ratio of current biomass to target biomass was used compute a Total Allowable Catch (TAC) for Pacific ocean perch. However, the most recent assessment indicated that the objectives of the rebuilding have been met.
For more information, contact Jonathan Heifetz at (907) 789-6054, James Ianelli at (206) 526-6510, or David Clausen at (907) 789-6049.
4. Thornyheads
b. Stock Assessment
GULF OF ALASKA
The 1996 NMFS survey indicated an increase in the biomass of thornyheads in the Gulf. There are discrepancies between increases in biomass as estimated from last three surveys (1990, 1993, and 1996) and model estimates of the stock which suggest a stable or slightly declining trend in abundance. Given the relatively low levels of natural mortality, the magnitude of removals, and the lack of strong recruitment signals, the increase may be viewed as inconsistent. The fact that the 1990 survey estimate was low for many of the rockfish species may indicate an unusual problem with that survey. The Groundfish Plan Team accepted the author’s recommendation of 1,700 mt for ABC and an overfishing level 2,440 mt within tier 3a. There is a concern that the current Gulf-wide management practice may be inappropriate and create localized depletion. Ideally, the catch apportionment by areas should reflect the biomass distribution assuming relative recruitment contributions are equal in each area.
For further information contact Dr. James Ianelli (206) 526-6510.
5. Sablefish
a. Research
GULF OF ALASKA
Sablefish Longline Survey
The AFSC has conducted an annual longline survey of sablefish and other groundfish in Alaska from 1987-96. The survey is a joint effort involving two divisions of the AFSC: ABL and RACE. It replicates as closely as practical the Japan-U.S. cooperative longline survey conducted from 1978-94 and also samples gullies not sampled during the cooperative longline survey. The eastern Bering Sea, Aleutian Islands region, and Gulf of Alaska were sampled during the cooperative longline survey, but the AFSC longline survey sampled only the Gulf of Alaska until 1996, when the Aleutian Islands region also was sampled. The eastern Bering Sea will be sampled in 1997. In 1996, 73 stations were sampled in the Gulf of Alaska and 14 stations were sampled in the Aleutian Islands region from 20 May to 19 August. Sixteen kilometers of groundline are set each day, containing 7,200 hooks baited with squid. The survey vessel was the chartered fishing vessel Alaskan Leader. Sablefish relative population weight in the Gulf of Alaska increased 18% from 1995-96, following a 7% decrease from 1994-95.
For more information, contact Michael Sigler at (907) 789-6037.
ABL Sablefish Tag Recovery Program
Processing tag recoveries and administration of the reward program continued during 1996. The database for sablefish tagged and released in Alaskan waters now contains 285,038 release records and 19,354 recovery records. Only about 800 tags were turned in during the year, which is the lowest number since 1982. This is probably due to the fact that, except for juveniles in inshore waters, no fish have been tagged since the final Japan-U.S. cooperative longline survey in 1994. Of the 800 tagged fish that were recovered, over one third had been at liberty for over ten years. Sablefish tagging will resume in 1997 on the domestic longline survey; we plan to tag and release approximately five percent of the catch in all areas of the survey.
Data on tag recoveries made by scientific vessels over the years were compiled during 1996 and are being used to obtain an estimate of tag reporting rate in the commercial fishery. This rate will be useful in quantifying migration patterns and population abundance estimates based on tagging data.
We are evaluating otolith ageing criteria for 2-9 year-old sablefish based on tag release and recovery data of sablefish that were tagged as juveniles. These data provided a relatively large sample (n=49) of known-age fish that were 2 to 9 years old. This sample of known age fish is being used to evaluate the accuracy of production ageing methods for sablefish.
For more information, contact Nancy Maloney at (907) 789-6060.
Juvenile Sablefish Studies
Juvenile sablefish studies have been conducted by ABL in Alaska since 1984 and were continued in 1996. Approximately 1,700 juvenile sablefish (age 1+) were tagged and released during cruises of the NOAA RV John N. Cobb at St. John Baptist Bay and Silver Bay, near Sitka, in May and July 1996. This was the twelfth consecutive year that relatively large numbers of juvenile sablefish have been found at St. John Baptist Bay. A young-of-the-year (YOY) sablefish study, which started in 1995, was conducted again in 1996 using the survey vessel Alaskan Leader opportunistically during the sablefish longline survey . A small-mesh surface gillnet was fished at night at offshore locations in the Aleutian Islands and Gulf of Alaska to capture YOY sablefish. Results from this study are unavailable at this time. Both the juvenile tagging and YOY sablefish studies are planned to be continued in 1997.
For more information, contact Thomas Rutecki at (907) 789-6051.
b. Stock Assessment
BERING SEA, ALEUTIAN ISLANDS, AND GULF OF ALASKA
Determination of sablefish abundance in Alaska is largely based on results of the annual sablefish longline survey. The sablefish population in Alaska's waters is still at a relatively healthy level, but with no strong recruitment evident in recent years, the population has slowly decreased since the mid 1980's. Most of the decrease has been concentrated at the outer range of sablefish in the Bering Sea and Aleutian Islands, while abundance in the Gulf of Alaska has not decreased dramatically.
Until 1997, yield estimates were determined from a stock reduction analysis modified to explicitly track estimates of exploitable biomass and provide an estimate of recruitment. The Bering Sea, Aleutian Islands, and Gulf of Alaska regions have been combined and analyzed as one stock since 1989. The recommended yield is then apportioned by management area according to estimates of current biomass using an exponential weighted average of past apportionment estimates. The ABC's for 1990-92 were computed by multiplying the F0.1 exploitation rate (0.116) by the estimate of exploitable biomass at the beginning of the fishing year. For ABC's for 1993 through 1996, an adjustable fishing rate strategy was adopted for sablefish, whereby the F35% fishing rate (that rate which would reduce the spawning biomass per recruit ratio to 35% of the unfished level) is adjusted in proportion to the ratio of current biomass to a target biomass level that is 35% of the unfished level (B35%). For 1997 ABC, new overfishing guidelines adopted by the NPFMC indicated that an adjusted F40% strategy be considered for sablefish.
In 1997, estimates of exploitable biomass and recruitment are determined from an age-structured model, which utilizes longline survey CPUE, survey length frequencies, and reported commercial catch in weight. Exploitable biomass for 1997 is estimated to range from 234,000 to 256,000 mt, depending upon inclusion of various scenarios in the model, such as possible under-reporting of commercial catches in 1989-90 and the level of likelihood weighting applied to the longline survey results. Yield ranged from 22,000 to 24,500 mt using the adjusted F40% fishing rate. If recent low levels of recruitment continue, these scenarios project that the population will decrease and the adjusted F40% strategy will result in yields between 11,300 mt and 13,700 mt within 10 years.
The yield from an adjusted F40% strategy represents a substantial increase over recent catches and ABC’s. Increasing ABC is inconsistent with a population that is considered to be decreasing and below target levels. Rather than increasing 1997 ABC, and then have it reduce rapidly in following years toward the predicted short-term equilibrium, it was recommended that current catch or ABC be incrementally adjusted toward the short-term equilibrium yield. Using 3 year increments, such equilibrium adjusted values would range from 16,800 to 17,600 mt for scenarios of under-reporting rates varying from 10% to 30% and a survey emphasis factor ranging from 1 to 7. The midpoint of these points, 17,200 mt, was recommended and adopted for 1997 ABC for the combined Alaskan stock.
An exponential weighting of regional sablefish relative population weights in the longline survey is used to apportion the combined ABC to regions. Applying this weighting scheme results in a percent distribution of the total ABC of 84.45 percent for the Gulf of Alaska, 7.61 percent for the Bering Sea, and 7.95 percent for the Aleutian Islands. Thus, a total stock ABC of 17,200 mt would be apportioned 14,525 mt, 1,308 mt, and 1,367 mt for the Gulf of Alaska, Bering Sea, and Aleutian Islands, respectively.
A similar exponential weighting is used to apportion the 1997 TAC within the Gulf of Alaska. This results in 12.79%, 44.15%, 16.61%, and 26.45% for the Western, Central, West Yakutat, East Yakutat/Southeast areas, respectively. The apportionment of the 14,525 mt Gulf of Alaska ABC results in 1,857 mt in the Western Area, 6,413 mt in the Central Area, 2,412 mt in the West Yakutat Area, and 3,842 mt in the East Yakutat/Southeast Area.
It is noted that the high ABC’s in recent years were the result of a few large year classes which occurred in the late 70's and early 80's. The last large year class occurred in 1984, and at present, there is no indication of another strong year class for at least another four years, at which time the population could be at historical low levels. The magnitude of the sablefish stock and the appropriate fishing rate largely depends on future recruitment, and little is known about the factors that determine recruitment levels.
For more information, contact Sandra Lowe at (206) 526-4230, Mike Sigler (907) 789-6037, or Jeff Fujioka at (907) 789-6026.
6. Flatfish
b. Stock Assessment
BERING SEA
Yellowfin sole
Two abundance estimators (trawl survey and stock synthesis) all indicate that the yellowfin sole resource increased slowly during the 1970s and early 1980s to a peak during the mid-1980s and that the resource has remained abundant and stable since that time. This trend is consistent with the facts that yellowfin sole is a slow-growing species which has been lightly exploited while experiencing average to strong recruitment during the past 15 years. The age-based Synthesis model used last year was updated for the present assessment. Exceptional recruitment from the 1981 and 1983 year classes has maintained yellowfin sole at a high level of abundance, although the stock is projected to decline in the near future.
Projected biomass of ages 7+ for 1997 is 2.53 million t. The recommended ABC was calculated according to an F40% (=0.11) harvest strategy, giving a projected 1997 catch of 233,000 t. The 1997 OFL for yellowfin sole is 339,000 t, corresponding to an F30% (=0.16) harvest strategy. Reliable estimates of FMSY or BMSY are not available for this stock.
Rock sole
An age-based Synthesis model was used to assess the rock sole stock. The time series of abundances estimated by the model parallels that from the trawl survey quite closely apart from the 1994 survey value, which appears to be an overestimate. Both the model and the survey indicate a dramatic increase in rock sole abundance throughout the 1980s and early 1990s. The model indicates that biomass has remained high and stable during the mid-1990s, with a projected 1997 level of 2.39 million t for ages 2+. The 1987 year class continues to appear exceptionally strong, and the 1990 year class appears to be above average as well.
Harvest levels remain well below the ABC level. Harvesting at an F40% (=0.15) strategy is used to compute ABC for this stock, giving a projected 1997 catch of 296,000 t. The OFL for this stock is defined by the F30% (=0.22) fishing mortality rate, which corresponds to a 1997 catch of 427,000 t. Reliable estimates of BMSY and FMSY are not available for this stock.
Flathead sole
Due to a change in the Bering Sea/Aleutian Islands directed fishing standards, the Council directed that flathead sole be separated from the "other flatfish" management category beginning in 1995. Trawl surveys indicate that the biomass of flathead sole has tripled since 1982, remaining high and stable since 1990. Except for a very high value in 1994, the survey biomass estimates have fluctuated between 570,000 t and 620,000 t since 1990. No assessment model has been developed for this stock and harvests remain well below ABC.
The authors use an F40% (=0.16) strategy in computing ABC for this stock, giving a projected 1997 catch of 101,000 t for the EBS and Aleutians combined. The OFL for this stock is defined by the F30% (=0.23) fishing mortality rate, which corresponds to a 1997 catch of 145,000 t for the combined areas. Reliable estimates of BMSY and FMSY are not available for this stock.
Other flatfish
Beginning with the 1995 fishing season, flathead sole were removed from the "other flatfish" complex, leaving Alaska plaice as the dominant member of the complex. The complex has remained at a stable, and presumably high, level of abundance throughout the modern history of the EBS survey time series (i.e., since 1982, when the present survey net configuration was adopted). Survey biomass estimates have fluctuated between 550,000 t and 850,000 t during this period, with the 1996 estimate coming in at a value of 589,500 t. In the present assessment, a biomass-based cohort analysis and an age-based Synthesis model are presented for Alaska plaice. The Synthesis model indicates that Alaska plaice recruitment was above average for all year classes spawned between 1969 and 1981, and below average for all but two year classes spawned since 1981. Based on the present assessment, the Plan Team believes that "other flatfish" qualify for management under tier 4 of Amendment 44. The Plan Team’s recommended 1997 ABC is based on an F40% harvest strategy (with F40%=0.20 for Alaska plaice and F40%= 0.16 for other members of the complex), giving a projected catch of 97,500 t.
The Plan Team’s OFL was determined from the tier 4 formula. Using an F30% value of 0.31 for Alaska plaice and 0.23 for other members of the complex, the 1997 OFL is 150,000 t.
Greenland turbot
The length-based Synthesis model used last year was updated for the present assessment. The protracted period of poor recruitment observed for this stock over the past several years continues. The model indicates that abundance is low and is expected to go lower. Although the assessment chapter includes an estimate of B40%, this estimate may not be reliable. Based on the present assessment (with the exception of the B40% estimate), the Plan Team believes that Greenland qualify for management under tier 4 of Amendment 44. The recommended 1997 ABC is based on an F40% (=0.35) harvest strategy, giving a projected catch of 16,800 t. However, the Plan Team also notes that the Council’s decision last year to set TAC (7,000 t) well below ABC is consistent with a conservative approach to management of a stock which is experiencing protracted poor recruitment.
The Plan Team’s OFL was determined from the tier 4 formula. Using an F30% value of 0.56, the 1997 OFL is 25,100 t.
Arrowtooth flounder
The length-based Synthesis model used last year was updated for the present assessment. Good recruitment from the 1977 year class and several year classes spawned during the 1980s combined with minimal harvest has maintained arrowtooth flounder at a high level of abundance, although the stock is projected to decline in the near future. Based on the present assessment, the Plan Team believes that arrowtooth flounder qualify for management under tier 4 of Amendment 44. The Plan Team’s recommended 1997 ABC is based on an F40% (=0.22) harvest strategy, giving a projected catch of 108,000 t.
The Plan Team’s OFL was determined from the tier 4 formula. Using an F30% value of 0.34, the 1997 OFL is 167,000 t.
GULF OF ALASKA
Management of the Gulf of Alaska flatfish resource has been divided into five categories by the North Pacific Fishery Management Council. These categories include: "shallow water flatfish", "deep water flatfish", arrowtooth flounder, flathead sole, and rex sole. This reclassification was made because of the significant difference in halibut bycatch rates in directed fisheries targeting on shallow and deep water flatfish species and also because of the dominant biomass of arrowtooth flounder which could cause the other flatfish species to be overfished if it was not separated from the group and managed under a separate TAC. Flathead sole are also managed under a separate TAC because they overlap the distributions of the shallow and deep water categories and rex sole were given a separate TAC because of a problem with POP bycatch in the directed rex sole fishery in 1993. Arrowtooth flounder are now assessed separately.
Due to halibut bycatch in commercial be well below their combined TAC, as in past years. In 1995 the shallow-water, deep-water, flathead sole, rex sole and arrowtooth flounder ABC apportionments were 17%, 15%, 10%, 51% and 10% harvested. Biomass estimates from the 1996 Gulf of Alaska trawl survey indicate that the total flatfish resource remains stable with no significant changes estimated for any species between survey years. Trawl survey size compositions indicate the continued presence of juvenile fish recruiting to the stock for rock sole, flathead sole and yellowfin sole. Recruitment patterns for rex and Dover sole are less clear.
The 1997 exploitable biomass is based on abundance estimated from a stock synthesis model, and is estimated to be greater than B40%; therefore, arrowtooth flounder is in tier 3a of the overfishing definitions. The F40% fishing mortality rate is 0.185 and was applied to the exploitable biomass estimate to determine an ABC estimate of 197,840 mt for arrowtooth flounder.
The overfishing level is set at the catch resulting from the F30% fishing mortality rate. For arrowtooth flounder F30% = 0.27 and the associated catch is estimated at 280,800 mt.
For 1997, the flatfish species are managed with a combined ABC of 283,400 t and a TAC of 78,990 t.
For further information, contact Jack Turnock (206) 526-6549.
7. Pacific whiting
WEST COAST
b. Stock Assessment
The most recent stock assessment of Pacific whiting was based on results of the stock synthesis model applied to data from the U.S. fishery, the Canadian fishery, NMFS acoustic surveys, NMFS triennial bottom trawl surveys, and Canadian Department of Fisheries and Oceans acoustic surveys. Substantive changes in the current assessment model from previous versions include: (1) the implementation of a single area model, (2) modeling the fisheries in the U.S. zone as a single combined fishery that displays time-varying selectivity, (3) the addition of the 1995 NMFS acoustic survey results and catch-at-age data for the U.S. and Canadian fisheries in 1995, and (4) a change in the target strength that is used to calibrate the acoustic surveys.
Biomass estimates from the acoustic survey for the 1977-89 period were re-estimated, due to the limited geographic coverage of these surveys. Deep water and northern expansion factors were used to scale up total acoustic back scatter. The revised acoustic biomass time series during this period averaged 31 percent higher than the original, even though use of the new "20 log L-68" target strength relationship tends to reduce biomass estimates by about 20 percent from previous values.
Projections for the 1995-97 period indicate that population biomass will range between 1.4-1.8 million mt. Application of the hybrid fishing mortality (F) harvest strategy to Pacific whiting population biomass was evaluated under low, moderate, and high exploitation rates. The hybrid F harvest strategy uses a constant F strategy when female spawning biomass is above the mean level, and a variable F strategy when female spawning biomass is below the mean. The moderate harvest rate strategy was preferred by the Council since deepwater and northern expansion factors were verified by data gathered during the 1995 acoustic survey. This represents a change from the last few years when the low harvest option was adopted due to uncertainty associated with the 1992 year acoustic survey results. Additional data were presented by the assessment author that the 1994 year class is large, which was strongly supported by statements from industry representatives. Consequently, yield projections were calculated based on the assumption that the 1994 year class is equal to the median recruitment of recent years, as well as the more favorable supposition that it is equal to the 75th percentile of recruitment over the 1972-95 period. To further bracket uncertainty, a projection was made which assumed that the 1994 year class is equal to the 87.5 percentile of historical recruitment.
The projected ABCs resulting from these three scenarios are: 241,000 t for an assumed median 1994 recruitment strength, 336,000 t for a 75th percentile recruitment, and 400,000 t for an 87.5 percentile recruitment. Arguments to adopt a conservative approach to selecting a final ABC included: (1) waiting an additional year to verify the strength of the 1994 year class will not result in an appreciable lost opportunity to harvest this cohort, as it will continue to increase in biomass through 1998, (2) past errors in identifying the strength of partially recruitmed whiting year classes (e.g., 1993) have required a lowering of ABC, (3) it is possible that the elevated abundance of the 1994 cohort observed in the fishery this ear is at least partially due to a northern shift in the distribution of 2-yr-old fish, a position supported by Canadian scientists, (4) stability in landings could be fostered by distributing the harvest of strong year classes over several years, and (5) higher landing of Pacific whiting will increase the overall bycatch of yellowtail rockfish at a time when that fishery is facing a major reduction in ABC.
Given these considerations, the Council’s Groundfish Plan Team recommended an ABC of 290,000 t for the U.S. and Canada combined. This specific recommendation represents a compromise between the first and second recruitment scenarios and amounts to a 25,000 t increase from the 1996 ABC (265,000 t).
For further information, contact Martin Dorn at (206) 526-6548.
10. Walleye pollock
a. Research
Acoustic Surveys - Midwater Assessment and Conservation Engineering (MACE) Task
BERING SEA
Between 18 July-2 September, 1996, an echo integration trawl (EIT) survey was conducted on the eastern Bering Sea shelf and slope to determine the distribution and abundance of walleye pollock (Theragra chalcogramma) as part of a triennial time series in conjunction with an annual bottom trawl survey. It encompassed shelf waters west and north of Port Moller, Alaska to the U.S./Russia convention line. In addition to the U.S., the Pacific Research Institute of Fisheries and Oceanography (TINRO), Vladivostok, Russia, conducted an AT survey of pollock in Russia’s exclusive economic zone (EEZ). The highest densities of pollock were observed from St. Matthew Island west to the U.S./Russia convention line. Moderate densities were observed between about 163o-166o W long. north of the Alaska peninsula and Unimak Island. A few isolated areas of very high pollock density were observed around the Pribilof Islands and between there and St. Matthew. From the western edge of Unimak Island to the Pribilofs relatively fewer pollock were observed. Pollock ranged in fork length (FL) from 12 to 71 cm. Dominant length modes were 17 cm and 36 cm north and west of the Pribilof Islands area, and around 50 cm near the Pribilofs and to the south and east. Nearly all fish less than 35 cm were observed northwest of the Pribilofs, with most near the U.S./Russia convention line. In the northwest, the 1992 year class (age 4) dominated, followed by the 1995 year class (age 1). South and east of the Pribilofs, the 1989 year class (age 7) was most numerous. The sex ratio by haul ranged from 31% to 59% female and averaged 46% female. No fish in spawning condition were encountered during the survey. Pollock numbered about 6.52 billion, with an estimated biomass of 2.31 million tons for the entire eastern Bering Sea survey area. Near the Pribilofs and in areas south and east, pollock biomass was 0.55 million tons and pollock numbered 0.63 billion. Northwest of the Pribilofs, pollock biomass was 1.76 million tons with 5.89 billion fish. The northwest area thus accounted for 76% of the total biomass and 90% of the total numbers of pollock estimated for the whole survey area.
Scientists from the midwater assessment program at the Alaska Fisheries Science Center (AFSC) investigated the population distribution and characteristics of spawning walleye pollock (Theragra chalcogramma) in the southeastern Aleutian Basin near Bogoslof Island between February 28 and March 11, 1997 using EIT survey techniques aboard the NOAA ship Miller Freeman. This research cruise was the ninth in a series that began in 1988 and has been continued annually with the exception of 1990 as part of long-term monitoring of Bering Sea pollock. In 1997, the cruise began and ended in Dutch Harbor, Alaska, and was a cooperative effort involving scientists from the United States, China, Poland and South Korea. Two passes were made through the area. Pass 1 began near Akutan Island and continued westward with 27 north-south transects covering about 1400 nmi. Ten midwater trawl hauls were made to sample pollock from the waters on or adjacent to transects. During pass 2, 18 transects covering about 525 nmi were run over the main spawning area, and 6 additional trawl hauls were completed. Pollock distribution was similar to that in 1996. Pollock were moderately concentrated in the eastern survey area between 165o 30-166o 30 W, and along the Aleutian Island chain between 167o 30-168o 30 W. Most pollock (60% of the biomass from pass 1) were distributed in several spawning aggregations 1-10 miles in horizontal extent and 200-400 m in vertical extent between 200-700 m in the water column from Umnak Island to the Islands of Four Mountains (169o-170o W). Fork lengths (FL) of pollock sampled in trawl hauls ranged from 33-66 cm, and average lengths increased from east to west. At the eastern most edge of the survey area, fish from a single haul averaged 44.0 cm/41.9 cm FL for females/males, respectively. Between 167o W and 166o W, average lengths were 50.0 cm /46.8 cm for females/males. West of 167o W, pollock averaged 55.4 cm/51.8 cm FL for females/males, respectively. Maturity composition data indicated that 84% of the females and 78% of the males were pre-spawning. The mean gonadosomatic index (gsi) for pre-spawning females was 0.20. Preliminary results suggested that total pollock abundance in the Bogoslof area was lower than it was in 1996.
GULF OF ALASKA
An EIT survey to assess the distribution and abundance of spawning walleye pollock within the Shelikof Strait area was conducted between Chirikof Island and Cape Chiniak during March 13-26, 1997. This is the sixteenth annual spawning stock survey of walleye pollock in the Shelikof Strait area since 1980 (no survey in 1982). A total of 1100 nmi of transect trackline and 30 hauls were completed during the survey. As in previous years, most spawning pollock were distributed along the western side of the Strait with greatest densities near Capes Kekurnoi and Kuliak. Fish were most abundant within 50-150 m of the bottom. The size distributions of pollock from hauls within the Strait generally exhibited dominant modes around either 26-29 cm or 50-56 cm fork length (FL). Eighty-eight percent of the females greater than 34 cm FL were either pre-spawning or spawning and only 6 percent were spent. Pollock from the 1994 year class (ca. 26-29 cm FL mode) formed a strong, well-defined midwater layer (150-200 m depth) which was broadly distributed from about Uyak Bay south to the Trinity Islands. The areal extent and strength of this layer of three-year old fish supports earlier EIT survey observations that the 1994 year class is relatively strong.
For more information contact Dr. Jimmie Traynor at (206) 526-4163.
Recruitment Processes (FOCI)
Fisheries-Oceanography Coordinated Investigations (FOCI), a NOAA cooperative research program between the Recruitment Processes Task of the RACE Division and the Pacific Marine Environmental Laboratory (PMEL) is designed to investigate the causes of recruitment variations in commercially important fish and shellfish. The program's focus is the well-defined spawning population of walleye pollock in Shelikof Strait, and walleye pollock stock structure and recruitment in the eastern Bering Sea. Bering Sea FOCI is part of the NOAA Coastal Ocean Program. Areas of research include field studies of eggs and larvae in relation to primary and secondary production and the physical environment, biochemical methods for assessing larval starvation and predation and stock structure, and pollock behavior. FOCI participated in nine cruises aboard the NOAA ship Miller Freeman and one aboard the NOAA ship Discoverer during 1996, five in the Shelikof Strait region of the Gulf of Alaska, and five in the Eastern Bering Sea to study the effects of the environment on the eggs and larvae of walleye pollock. We also conducted a study of young-of-the-year juvenile pollock in the Bering Sea near the Pribilof Islands in late summer, and participated in a cruise aboard the Japanese fisheries research ship Oshoro Maru in the Eastern Bering Sea during the summer. Laboratory studies on reared pollock larvae were conducted to calibrate biochemical indices, and estimate feeding, digestion, and gastric evacuation rates. Eggs were spawned from fish trawled in the Shelikof Strait and Bogoslof Island area, maintained in refrigerators aboard ship, and then transported in thermos jugs to the culture center at Sand Point in Seattle.
For more information contact Dr. Art Kendall at (206) 526-4108.
b. Stock Assessment
BERING SEA AND ALEUTIAN ISLANDS
As in previous years, this year’s pollock assessment includes two models based on cohort analysis. It also includes a Bayesian alternative model presented in an appendix. The Plan Team again used the "solver" version of cohort analysis for its ABC, OFL, and projected biomass values. The Plan Team accepts the estimates of FMSY (0.38) and BMSY (6.00 million t) given in the assessment. Based on the present assessment (including the estimates of FMSY and BMSY), the Plan Team believes that this stock qualifies for management under tier 2 of Amendment 44. Under tier 2, FMSY is the maximum allowable ABC fishing mortality rate, given that the stock’s biomass is projected to remain above BMSY for the coming year. However, their is concern about the possible magnitude of Russian pollock harvests in areas where the fish are likely part of the same stock prosecuted by the EBS fishery. In particular, potentially large harvests of 2-year-old pollock are of concern, as these fish might otherwise be expected to recruit to the EBS fishable population. Also, the number of age 2 fish encountered by this year’s hydroacoustic survey was smaller than expected and seemed to be clustered near the Navarin region (i.e., near the northwestern edge of the U.S. EEZ). Because of these concerns, the Plan Team’s recommended ABC is based on the F40% (=0.30) fishing mortality rate, which is substantially below the FMSY rate. Based on the "solver" cohort analysis model, harvesting at the F40% rate gives a projected 1997 catch of 1,130,000 t, which is the Plan Team’s recommended ABC. The F40% harvests projected for 1997 by the other cohort analysis model and the Bayesian alternative model are also very close to this value. Although the recommended 1997 ABC is very close to last year’s ABC, both the cohort analysis model and the Bayesian alternative model project significant decreases in ABC for the years following 1997.
The overfishing level was determined from the tier 2 formula, where FOFL = FMSY ´ F30% / F40% = 0.38 ´ 0.46/0.30 = 0.58. Based on the "solver" cohort analysis model, harvesting at a fishing mortality rate of 0.58 gives a projected 1997 catch of 1,980,000 t, which is the Plan Team’s OFL.
Aleutians:
An age-structured model was used for pollock in the Aleutian Islands. Based on the present assessment, the Plan Team believes that Aleutian pollock qualify for management under tier 4 of Amendment 44. The Plan Team’s recommended ABC is based on the low end of the model’s estimated biomass (100,000 t) and an F40% value of 0.38, giving a projected 1997 catch of 28,000 t. The directed pollock fishery in the Aleutians is likely to have only a short opening and may be difficult to manage if TAC is 28,000 t or less.
The Plan Team’s OFL was determined from the tier 4 formula. Using an F30% value of 0.57, the 1997 OFL is 38,000 t.
Bogoslof:
Projected biomass was computed by applying a natural mortality rate of 0.20 to the 1996 survey biomass estimate of 682,000 t, giving a 1997 projection of 558,000 t. Applying an F40% rate of 0.27 gives a projected 1997 catch of 115,000 t. The Plan Team notes that the Council recommended against allowing a target pollock fishery in the Bogoslof district during 1996, and suggests that this recommendation be continued for 1997.
The Plan Team’s OFL was determined from the tier 4 formula. Using an F30% value of 0.37, the 1997 OFL is 157,000 t.
For further information contact Dr. Vidar Wespestad, (206) 526- 4249.
GULF OF ALASKA
Relative to the 1996 SAFE, new sources of information include: a) the 1996 triennial bottom trawl survey biomass estimate; b) length frequency data from the 1996 bottom trawl survey; c) the 1996 Shelikof Strait hydroacoustic biomass estimate; d) length frequency data from the 1996 hydroacoustic survey; e) age composition data from the 1995 fisheries; f) updated estimates of discard and catch for 1995 and 1996; and g) results of a sensitivity analysis exploring several assumptions about the emphasis applied to survey biomass estimates and the catchability of the bottom trawl survey.
The 1996 Shelikof Strait biomass estimate is 745,400 mt (similar to the estimate of 725,200 mt from the 1995 survey). These values were adjusted in the stock assessment to be comparable to estimates from the old hydroacoustic system in order to provide a time series of a relative abundance index. The sensitivity analysis explored the impact of constraining the hydroacoustic survey selectivity to be asymptotic. The findings of a reduced fit to all data components except the hydroacoustic length compositions suggested that the hydroacoustic survey selectivity should not be constrained to be asymptotic.
Length frequency data from the 1990 to 1996 hydroacoustic surveys showed the progression of the strong 1988 year class through the population. In the 1995 and 1996 surveys, evidence of a strong 1994 year class was also apparent. In 1996, 82.2% of the population numbers were 16-25 cm (age 2, 1994 year class). Age 1 (<16 cm) pollock of the 1995 year class represented 1.3% of the population numbers.
The biomass estimate for the Western/Central area from the 1996 bottom trawl survey was 653,900 mt, similar in magnitude to previous survey estimates. Length frequency distributions from the 1996 bottom trawl survey showed the strong 1994 year class in the Western and Central Gulf. In the Eastern Gulf and the Shumagin region, a second smaller mode (assumed to be the 1995 year class) was observed. It was noted that the 1996 hydroacoustic survey found relatively low numbers of 1 year olds from the 1995 year class.
The age compositions from the 1993 bottom trawl survey and the 1995 fishery revealed strong 1988 and 1989 year classes. The 1989 year class in the Bering Sea has been shown to be strong. The presence of the strong 1989 year class found in the Shumagin, Chirikof and Kodiak areas suggests that mixing of pollock stocks may occur between the Bering Sea and the Gulf of Alaska. Alternatively, 1989 oceanic conditions may have favored recruitment in the Western Gulf of Alaska more than the Central area.
The current assessment model is similar to last year, except for a reduction in the number of length categories, inclusion of the 1984 bottom trawl biomass estimate, and the use of separate fishery selectivity vectors for 1992-1996. The previous model configuration had assumed a single fishery selectivity vector for 1991-1996. The recent change was made because the inclusion of the 1996 bottom trawl survey in the previous model yielded poor fits to the recent fishery age composition data.
Estimates of various fishing mortality rates based on biological reference points were determined from the stock synthesis model. The estimated F30%, F35%, and F40% full-selection fishing mortality rates were 0.468, 0.390, and 0.329, respectively. The 1997 3+ biomass was estimated at 1,105,420 mt from the current stock synthesis analysis. Additionally, the B40% female spawner biomass (289,700 mt) was higher than the projected 1997 female spawner biomass of 237,300 mt. Average historical recruitment from the 1963-94 year classes (the 1994 year class was represented by the median of the upper quartile of recruitment estimates) was used in the calculation of B40%. The Plan Team asked the authors to explore other measures of central tendency, specifically the geometric mean of historical recruitment, in the future assessment. It was noted that with a stock such as pollock which exhibits extremely variable recruitment, the calculation of B40% and F40% would be quite sensitive to average long term recruitment assumptions.
The assessment included an exploration of the long term productive potential of the pollock stock with a stochastic age structured simulation and different recruitment scenarios. The tradeoffs between increased yield and the risk of falling below an estimated threshold were evaluated and the fishing mortality rate selected from this simulation was 0.32 (full selection value). This fishing mortality rate (0.30 in last year’s assessment) was used to estimate the 1996 ABC. Pollock fall under tier 3 of the ABC/OFL guidelines, thus FABC cannot exceed the F40% fishing mortality rate adjusted by the ratio of current spawner biomass to B40%. The FABC (F40%adjusted) fishing mortality rate is 0.275, results in a yield of 74,400 mt for the Western/Central Gulf, and is the recommended 1997 Western/Central ABC.
The Groundfish Plan Team recommended the ABC be apportioned according to the biomass distribution of the exploitable population (>20 cm) in the 1996 bottom trawl survey: 25% in the Shumagin area (18,600 mt), 42% in the Chirikof area (31,250 mt), and 33% in the Kodiak area (24,550 mt). Relative to the 1993 distribution, the current biomass distribution has increased in the Kodiak area and decreased in the Shumagin area, and is similar to the 1990 survey distribution.
The overfishing mortality rate (0.41) is F30% adjusted by the ratio of current spawner biomass to B40%, and corresponds to a harvest of 103,500 mt for the Western and Central Gulf of Alaska. Therefore, pollock are not considered overfished at the ABC level.
There is no new information to set an ABC for the Eastern Gulf. Lack of adequate age composition data has precluded any age-structured analysis similar to that conducted for the W/C areas. However, analysis of Eastern Gulf length frequency data show that recruitment patterns appear similar to that observed in the W/C Gulf. Thus, the Team agreed that it would be appropriate to apply the ratio of W/C ABC to 1996 W/C survey exploitable biomass to the Eastern Gulf 1996 exploitable biomass estimate. The recommended Eastern Gulf ABC is 5,580 mt. Similarly calculated, the overfishing level for the Eastern Gulf is 7,770 mt.
The exploitable biomass estimates from 1994 and 1995 are from the stock synthesis (SS) model as determined in those years. The 1996 mid-year biomass is estimated at 574,000 mt from the current SS analysis. Comparisons of the 1996 biomass to previous years' levels should be made with biomass levels from the revised hindcast in the current assessment.
For more information contact Dr. Anne Hollowed 526-4223.
D. Other related studies
Sea Floor Habitat Studies:
Effects of Bottom Trawling in the Eastern Gulf of Alaska
This past year, ABL initiated a study to examine the effects of trawling on hard bottom areas of the eastern Gulf of Alaska. The objective was to determine whether a bottom trawl outfitted with tire gear on the foot rope causes changes to the sea floor and associated epifauna. We used both a commercial trawler and a two-man submersible in this investigation. The trawler was fitted with a Nor’eastern bottom trawl equipped with tire gear. Most trawling was on the outer continental shelf in low-profile habitat (pebble/cobble) at depths of 200–220 m. After each trawl track was completed, the submersible descended to the sea floor and located the trawl path. Currently, videotape data are being analyzed, initially concentrating on habitat classification, sessile and motile epifauna in trawled vs. reference transects, impacts to epifauna, and comparisons of trawl bycatch with organisms in situ. Study sites were marked and observations will be repeated in 1997 to document longer term recovery/damage.
For more information, contact Linc Freese at (907) 789-6045, Ken Krieger at (907) 789- 6053, or Jonathan Heifetz at (907) 789-6054.
Retrospective Analysis of Commercial Trawl Data and Benthic Community Structure
In 1996, a study was begun to determine the structure of benthic communities in Alaskan waters and possible trawl fishery effects on these communities based on data from both the commercial trawl fishery and trawl surveys. The objectives of this study are to 1) describe the geographic and temporal patterns of trawl fishery effort in the Gulf of Alaska and Aleutian Island regions, 2) describe the major benthic communities by their component species and associations based on trawl survey data, and 3) to the extent possible, determine possible trawl fishery influences on benthic community structure by comparing benthic community structure in heavily trawled areas to lightly trawled areas. This study is being carried out under auspices of ABL via a grant to the Cooperative Institute for Arctic Research (CIFAR) at the University of Alaska Fairbanks.
For more information, contact Cathy Coon (907) 789-6604 or Jonathan Heifetz (907) 789-6054.
Seabed Composition as it Relates to Survey Design
The RACE West Coast Groundfish team has been conducting a retrospective analysis of our triennial bottom trawl surveys conducted along the west coast from 1977-1995. While there are many different portions of this project, they are all related and hopefully the combined results will lead to a better understanding of how our survey samples the groundfish populations.
The first objective is to identify areas where we have been unable to successfully use our bottom trawl nets. This involves plotting the locations of poor performance hauls (trawl gear ripped or hung-up on bottom) and stations which were skipped because the bottom was too rough. Preliminary results show clustering of bad tows in some areas. For example, in the shallow stratum off northern Washington (US Vancouver area, 55-183 m), approximately 42% of planned stations were not sampled successfully (1986-95). We are working with Washington State Department of Fish and Wildlife scientists to explore weather the abundance of some important commercial groundfish species are different in the untrawlable vs. trawlable areas. Species of particular interest in this study include lingcod (Ophiodon elongatus) and canary rockfish (Sebastes pinniger).
Along with delineating untrawlable areas, we plan to create a map of surficial sediments throughout our west coast survey area. This will be the first such map created using original data sources with sediments divided into constituent components (%gravel, %sand, %silt, and %clay). Previous maps have used data coded by a ternary diagram or only visually classified samples. To date we have accumulated about 2,000 data points, with good coverage of the northern half of the survey area and weaker coverage of the southern half. We are working with the Geological Survey of Canada and the United States Geological Survey towards completing this goal. All data will be imported into a GIS package so that we can use spatial statistics to interpolate the data and produce a map which can be easily updated.
We also hope to conduct an assemblage analysis on the groundfish species, showing which species tend to occur together. Depth, bottom water temperature and sediment texture will be used to further define these assemblages. Age and length data from our catches, not normally included in assemblage analysis studies, may help us further refine these assemblages. Once completed, we hope to use that information to identify stations with similar catches, group the stations into strata, and then compare these strata to our current stratification system, based on depth and latitude. By minimizing differences in species composition between strata, more accurate estimates of species abundance with lower variance should be produced.
For more information, contact Mark Zimmermann, 206-526-4119.
Effects of Trawling on Demersal Invertebrates
At the end of the standard Bering Sea Crab/Groundfish Survey an experiment was performed to estimate the effect of trawling on the bottom by sampling demersal invertebrate species in areas primarily closed to trawling and adjacent areas subject to intensive commercial trawling. Fifty-two pairs of tows were made in inner Bristol Bay around the perimeter of the red king crab Protection Zone 1. Analyses are continuing.
For more information, contact Gary Walters, 206-516-4143.
Remote Acoustic Substrate Typing
Experiments with acoustic bottom-typing equipment commenced in 1996 in conjunction with the hydroacoustic survey of the Bering Sea. Engineering problems with the interface between sounder and analysis equipment were discovered and have been solved with manufacturer/NMFS cooperative work. Phase 2 of the project will continue during the 1997 Bering Sea Crab/Groundfish Survey.
For more information, contact Robert McConnaughey, 206-526-4150.
Trawl Survey Methodology
The RACE Division has been active in several studies of the sampling methodology related to bottom trawl surveys, including the effects of herding and escapement on the catch rates observed during surveys, the effect of changing survey trawl haul duration, alternative methods of subsampling large survey catches, and matters related to bycatch. Underwater video and scanning sonar were used to study the behavior of fish encountering trawl gear with the purpose of detecting species and size differences which could be exploited to reduce bycatch. This technology, combined with equipment for measuring trawl operational parameters, was also applied to studies of survey trawl effectiveness.
Escapement of Flatfish Under the Footrope of the Nor’eastern Roller Trawl
Scientists in the RACE Division’s Groundfish Task conducted a trawl efficiency experiment during the 1996 Gulf of Alaska triennial bottom trawl survey of groundfish resources. The experiment was designed to measure the proportion of fish escaping under the footrope of the survey trawl. This study is part of a series of experiments designed to quantify the efficiency of our survey trawls. Our overall goal is to be able to more accurately estimate groundfish abundance with area-swept trawl surveys.
We used the chartered vessel F/V Golden Dawn to conduct this experiment on Portlock Bank, off Kodiak Island. We used the RACE Divsion standard, high-opening Noreastern trawl used for all RACE Division continental shelf trawl surveys in the West Coast, Gulf of Alaska, and Aleutian Islands. Roller gear is used in conjunction with this trawl to enable sampling in areas of fairly rough bottom. Concerns have been raised that the roller gear allows a relatively clear path of escape for groundfish, particularly flatfish.
Our experiment employed a second, smaller trawl attached underneath the Noreastern to capture any fish passing under the footrope of the Noreastern net. This secondary trawl, or bag trawl, was fashioned after those used in similar studies conducted by Norwegian and Canadian fishery scientists. It utilized heavy chain strung with 13 cm (5") rubber disks to ensure steady contact with the sea floor. Camera observations showed that the bag trawl interfered minimally, if at all, with the normal operation or fishing configuration of the Noreastern trawl.
We successfully completed 34 hauls without snagging the bottom or tearing up the gear. Catches from the main trawl and the bag trawl were sorted separately and the fish weighed, counted, and measured. Preliminary results show that one-half of the bag trawl catch (by weight) was invertebrates, compared to only a trace amount in the main trawl, indicating sound bottom contact by the experimental net. Flatfish species, skates, and spiny dogfish dominated the bag trawl samples, whereas catches of roundfish were slight. The species which the Noreastern was least effective in catching was Dover sole. The proportion of fish escaping capture by the main trawl was estimated for the five most commonly occurring species. The percent escapement for arrowtooth flounder, Dover sole, rex sole, flathead sole, and Pacific cod were (by weight) 7.4, 55.1, 14.1, 24.7, and 5.3%, respectively. Percent escapement by numbers for the same species was estimated to be 19.5, 53.8, 17.5, 33.6, and 6.1%.
Size selectivity curves were derived for a few of the more commercially important species. These results indicate that the Noreastern trawl, in general, has a tendency to pass over smaller flatfish. The exception to this was Dover sole.
For further information, contact Peter Munro, (206) 526-4292 or Ken Weinberg, (206) 526-6109.
The Effect of Artificial Light on Escapement Beneath a Survey Trawl
Escapement under the footrope of a trawl has been estimated by attaching an auxiliary bag underneath the trawl to capture the escaping fish. Auxiliary bags, however, are relatively fragile, limiting the procedure to areas of smooth substrate. An alternative method under investigation by the Alaska Fisheries Science Center is to directly count escaping fish by attaching a video camera and an artificial light source to the trawl. An advantage to this technique is that it can accompany the trawl over a variety of depths and bottom conditions inhabited by varying fish assemblages. However, because most survey stations are at depths greater than natural light can penetrate for low-light camera use, artificial light is necessary. One potential shortcoming of this approach is that the light emitted might alter fish behavior and thereby bias estimates of escapement. The effect of the artificial light was examined by attaching a 50 watt halogen lamp onto a trawl fitted with an auxiliary bag. A paired experiment (lighted and unlighted footrope) was then used to test whether the escapement rate changed with the presence of the light under a variety of ambient light conditions.
For further information, contact Ken Weinberg, (206) 526-6109.
APPENDIX I
Recent Publications and Reports Pertaining to Groundfish and Marine Habitats by Authors at the Alaska Fisheries Science Center
These reports are primarily products of the RACE Division, REFM Division, and the Auke Bay Laboratory.
ANDERL, D. M., A. NISHIMURA, and S. A. LOWE.
1996. Is the first annulus on the otolith of the Atka mackerel, Pleurogrammus monopterygius, missing? Fish. Bull., U.S. 94:163-169.
BAILEY, K. M., R. D. BRODEUR, and A. B. HOLLOWED.
1996. Cohort survival patterns of walleye pollock, Theragra chalcogramma, in Shelikof Strait, Alaska: A critical factor analysis. Fish. Oceanogr. 5(Suppl. 1):179-188.
BAILEY, K. M., S. J. PICQUELLE, and S. M. SPRING.
1996. Mortality of larval walleye pollock Theragra chalcogramma in the western Gulf of Alaska, 1988-91. Fish. Oceanogr. 5(Suppl. 1):124-136.
BAILEY, K. M., A. L. BROWN, M. M. YOKLAVICH, and K. L. MIER.
1996. Interannual variability in growth of larval and juvenile walleye pollock Theragra chalcogramma in western Gulf of Alaska, 1983-91. Fish. Oceanogr. 5(Suppl. 1):137-147.
BRODEUR, R. D., and K. M. BAILEY.
1996. Predation on the early life stages of marine fishes: a case study on walleye pollock in the Gulf of Alaska, p. 245-259. In Y. Watanabe, Y. Yamashita, and Y. Oozeki (editors), Survival Strategies in Early Life Stages of Marine Resources. A.A. Balkema Press, Rotterdam, Netherlands.
BRODEUR, R. D., and M. T. WILSON.
1996. A review of the distribution, ecology and population dynamics of age-0 walleye pollock in the Gulf of Alaska. Fish. Oceanogr. 5(Suppl. 1):148-166.
BRODEUR, R. D., B. W. FROST, S. R. HARE, R. C. FRANCIS, and W. J. INGRAHAM, JR.
1996. Interannual variations in zooplankton biomass in the Gulf of Alaska, and covariation with California Current zooplankton biomass. CalCOFI Rep. 37:80-99.
BRODEUR, R. D., J. M. NAPP, M. T. WILSON, S. J. BOGRAD, E. D. COKELET, and J. D. SCHUMACHER.
1996. Acoustic detection of mesoscale biophysical features in the Shelikof sea valley, and their relevance to pollock larvae in the Gulf of Alaska. Fish. Oceanogr. 5(Suppl. 1):71-80.
BRODEUR, R. D., S. J. PICQUELLE, D. M. BLOOD, and N. MERATI.
1996. Walleye pollock egg distribution and mortality in the western Gulf of Alaska. Fish. Oceanogr. 5(Suppl. 1):92-111.
EBBESMEYER, C. C., R. CHIANG, A. COPPING, G. M. ERICKSON, R. HORNER, W. J. INGRAHAM, JR., and L. NISHITANI.
1995. Decadal covariations of Sequim Bay paralytic shellfish poisoning (PSP) with selected Pacific Northwest environmental parameters,p. 415-421. In Puget Sound Research ‘95 Proceedings, January 12-14, 1995. Available from Puget Sound Water Quality Authority, P.O. Box 40900, Olympia, WA 98504-0900.
GILROY, H., P. J. SULLIVAN, S. M. LOWE, and J. M. TERRY.
1996. Preliminary assessment of the halibut and sablefish IFQ programs in terms of nine potential conservation effects, prepared as one of a group of studies completed by NMFS, IPHC, USCG, and the State of Alaska.
HAAGA, J. A., and B. G. STEVENS.
1996. Reproductive conditions, fecundity, and size at maturity for the Arctic lyre crab (Hyas coarctatus) in the eastern Bering Sea, p. 443-444. In Proceedings of the International Symposium on Biology, Management, and Economics of Crabs from High Latitude Habitats. Alaska Sea Grant College Program Report No. 96-02, University of Alaska Fairbanks.
HEIFETZ, J.
1996. Dynamics of a migratory fish population with applications to the management of sablefish in the northeast Pacific Ocean. Doctoral dissertation. University of Alaska Fairbanks, Juneau AK. 127 p.
HEIFETZ, J. (editor).
1997. Workshop on the potential effects of fishing gear on benthic habitat. U.S. Dep. Commer., AFSC Processed Report 97-04. 17 p.
HERMANN, A. J., W. C. RUGEN, P. J. STABENO, and N. A. BOND.
1996. Physical transport of young pollock larvae (Theragra chalcogramma) near Shelikof Strait as inferred from a hydrodynamic model. Fish. Oceanogr. 5(Suppl. 1):58-70.
HERMANN, A. J., S. HINCKLEY, B. A. MEGREY, and P. J. STABENO.
1996. Interannual variability of the early life history of walleye pollock near Shelikof Strait as inferred from a spatially explicit, individual-based model. Fish. Oceanogr. 5(Suppl.1):39-57.
HONKALEHTO, T., and N. WILLIAMSON.
1996. Echo integration-trawl survey of walleye pollock (Theragra chalcogramma) in the south-eastern Aleutian Basin during February and March 1995. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-65, 57 p.
HOWELL-KUBLER, A. N., E. J. LESSARD, and J. M. NAPP.
1996. Springtime microprotozoan abundance and biomass in the southeastern Bering Sea and Shelikof Strait, Alaska. J. Plank. Res. 18:731-745.
IANELLI, J. N., and T. K. WILDERBUER.
1995. Greenland turbot (Reinhardtius hippoglossoides) stock assessment and management in the eastern Bering Sea, p. 407-441. In Proceedings of the International Symposium on North Pacific Flatfish. Alaska Sea Grant Program. AK-SG-95-04.
JOHNSTON, R. S., L. E. QUEIROLO, and Z. ZHANG.
1996. Competition and the market for fisheries access under extended jurisdiction. Northwest J. Business Econ., September 1996, p. 55-69.
KENDALL, A. W. JR., and A. J. MEARNS.
1996. Egg and larval development in relation to systematics of Novumbra hubbsi, the Olympic mudminnow. Copeia 1996(3):684-695.
KENDALL, A. W., JR., J. D. SCHUMACHER, and S. KIM.
1996. Walleye pollock recruitment in Shelikof Strait: Applied fisheries oceanography. Fish. Oceanogr. 5(Suppl. 1):4-18.
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1996. Perspectives on the relationship between otolith growth and the conversion of isotope activity ratios to fish ages. Can. J. Fish. Aquat. Sci. 52:2296-2303.
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1996. Kalman filtering the delay-difference equation: Practical approaches and simulations. Fish. Bull., U. S. 94:678-691.
KIMURA, D.K., and H.H. ZENGER, JR.
1997. Standardizing sablefish (Anoplopoma fimbria) longline abundance indices by modeling the log-ratio of paired comparative fishing cpue's. ICES J. of Marine Science, 54:48-59.
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1996. Oregon, Washington, and Alaska exports of edible fishery products, 1994. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-63, 49p.
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1996. Oregon, Washington, and Alaska Exports of Edible Fishery Products, 1995. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-66, 48p.
KINOSHITA, R. K., A. GREIG, and J. M. TERRY.
1966. Economic status of the groundfish fisheries off Alaska, 1994. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-62, 102 p.
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1996. Food habits of key groundfish species in the eastern Bering Sea slope region. U.S. Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-67, 111 p.
LAUFER, H., J. S. B. AHL, P. TAKAC, G. SCOTT, B. STEVENS, J. E. MUNK, and S. A. PAYNE.
1996. Hormone and reproductive strategies in spider crabs with emphasis on commercially important species, p. 383-387. In Proceedings of the International Symposium on Biology, Management, and Economics of Crabs from High Latitude Habitats. Alaska Sea Grant College Program Report No. 96-02, University of Alaska Fairbanks.
LAUTH, R. R., and R. J. OLSON.
1996. Distribution and abundance of larval Scombridae in relation to the physical environment in the northwestern Panama Bight. IATTC Bulletin Vol 21, No. 3, 167 p.
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1995. Male size and female reproduction in Dungeness crab in Glacier Bay, Alaska,p. 203-208. In Proceedings of the Third Glacier Bay Science Symposium, 1993, D.R. Engstrom (editor), National Park Service, Anchorage, Alaska.
LIVINGSTON, P.A.
1996. Alaska Gyre Model- Miscellaneous Fish. In: D. Pauly and V. Christensen (eds). Mass-Balance Models of North-eastern Pacific Ecosystems. The Fisheries Centre, University of British Columbia, 2204 Main Mall, Vancouver, B.C. Canada, V6T 1Z4.
LIVINGSTON, P.A.
1996. Southern B.C. Shelf Model - Pacific cod and sablefish. In: D. Pauly and V. Christensen (eds). Mass-Balance Models of North-eastern Pacific Ecosystems. The Fisheries Centre, University of British Columbia, 2204 Main Mall, Vancouver, B.C. Canada, V6T 1Z4.
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1996. Interdecadal comparisons of walleye pollock, Theragra chalcogramma, cannibalism in the eastern Bering Sea. P. 115-124. In: Brodeur, R.D. P.A. Livingston, T.R. Loughlin, and A.B. Hollowed. Ecology of Juvenile Walleye Pollock, Theragra chalcogramma. U.S. Dept. Commerce, NOAA Tech. Rept. NMFS 126. 227p.
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1996. Bitter crab hemolymph studies: indications of host physiological condition, p. 549-562. In Proceedings of the International Symposium on Biology, Management, and Economics of Crabs from High Latitudes. Alaska Sea Grant College Program Report No. 96-02, University of Alaska Fairbanks.
MACINTOSH, R. A. , B. G. STEVENS, J. A. HAAGA, and B. A. JOHNSON.
1996. Effects of handling and discarding on mortality of Tanner crabs (Chionoecetes bairdi), p. 577-590. In Proceedings of the International Symposium on Biology, Management, and Economics of Crabs from High Latitude Habitats. Alaska Sea Grant College Program Report No. 96-02, University of Alaska Fairbanks.
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1996. Principles for the conservation of wild living resources. Ecol. Appl. 6:338-362.
MCCONNAUGHEY, R. A.
1995. Changes in geographic dispersion of eastern Bering Sea flatfish associated with changes in population size,p. 385-405. In Proceedings of the International Symposium on North Pacific Flatfish. Alaska Sea Grant Program. AK-SG-95-04, University of Alaska Fairbanks.
MEGREY, B. A., and E. MOKSNESS (editors).
1996. Computers in Fisheries Research. Chapman Hall, London, 254 p.
MEGREY, B. A., A. B. HOLLOWED, S. R. HARE, A. MACKLIN, and P. J. STABENO.
1996. Contributions of FOCI research to forecasts of year-class strength of walleye pollock in Shelikof Strait, Alaska. Fish. Oceanogr. 5(Suppl. 1):189-203.
MEYERS, T. R., J. F. MORADO, A. K. SPARKS, G. H. BISHOP, T. PEARSON, D. URBAN, and D. JACKSON.
1996. Distribution of bitter crab syndrome in Tanner crabs Chionoecetes bairdi, C. opilio from the Gulf of Alaska and the Bering Sea. Dis. Aquat. Org. 26: 221-227.
MORADO, F., and E. B. SMALL.
1994. Morphology and stomatogenesis of Mesanophrys pugettensis n. sp. (Scuticociliatida: Orchitophryidae), a facultative parasitic ciliate of the Dungeness crab, Cancer magister (Crustacea: Decapoda). Trans. Am. Microsc. Soc. 113(3):343-364.
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1996. Timing and duration of the mating and molting season for shallow water Tanner crab (Chionoecetes bairdi), p. 341-347. In Proceedings of the International Symposium on Biology, Management, and Economics of Crabs from High Lattitude Habitats. Alaska Sea Grant College Program Report No. 96-02, University of Alaska Fairbanks.
NAPP, J. M., L. S. INCZE, P. B. ORTNER, D. L. W. SIEFERT, and L. BRITT.
1996. The plankton of Shelikof Strait, Alaska: Standing stock, production, mesoscale variability and their relevance to larval fish survival. Fish. Oceanogr. 5(Suppl. 1):19-38.
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1995. Spawning and maturation of female yellowfin sole in the eastern Bering Sea, p. 35-50. In Proceedings of the International Symposium on North Pacific Flatfish. Alaska Sea Grant Program. AK-SG-95-04.
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1995. Nearshore distribution and abundance of Dungeness crabs in Glacier Bay National Park, Alaska,p. 196-202. In Proceedings of the Third Glacier Bay Science Symposium, 1993, D.R. Engstrom (ed.), National Park Service, Anchorage, Alaska.
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1996. Contamination of intertidal and subtidal sediments by oil from the Exxon Valdez in Prince William Sound. In S. D. Rice, R. B. Spies, D. A. Wolfe, and B. A. Wright (editors). Proceedings of the Exxon Valdez Oil Spill Symposium. Am. Fish. Soc. Symp. 18:61-93.
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1996. Dispersion of adult Cancer magister at Glacier Bay, Alaska: Variation with spatial scale, sex, and reproductive status, p. 209-227. In Proceedings of the International Symposium on Biology, Management, and Economics of Crabs from High Lattitude Habitats. Alaska Sea Grant College Program Report No. 96-02, University of Alaska Fairbanks.
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1996. Behavioural determinants of distribution and survival in early stages of walleye pollock, Theragra chalcogramma: A synthesis of experimental studies. Fish. Oceanogr. 5(Suppl. 1):167-178
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1996. Observations on the biology of the lithodid crab Paralomis spinosissima from the Southern Ocean near South Georgia, p. 627-647. In Proceedings of the International Symposium on Biology, Management, and Economics of Crabs from High Latitude Habitats. Alaska Sea Grant College Program Report No. 96-02, University of Alaska Fairbanks.
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1996. Food deprivation affects vertcal distribution and activity of a marine fish in a thermal gradient: Potential energy-conserving mechanisms. Mar. Ecol. Prog. Ser. 133:43-55.
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1996. Contribution to the biology of the grooved and triangle Tanner crabs, Chionecetes tanneri, and c. Angulatus, in the eastern Bering Sea. Fish. Bull., U.S. 94:348-357.
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1996. Observed patches of walleye pollock eggs and larvae in Shelikof Strait, Alaska: Their characteristics, formation and persistence. Fish. Oceanogr. 5(Suppl. 1):81-91.
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1996. A statistical test for a difference between the spatial distributions of two populations. Ecology 75-80.
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1996. Variations in larval walleye pollock feeding and condition: A synthesis. Fish. Oceanogr. 5(Suppl. 1):112-123.
TRAYNOR, J. J.
1996. Target-strength measurements of Walleye pollock
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1995. Discard mortality rates of Pacific halibut:Fishery differences and trends during 1990-1993, p. 611-622. In Proceedings of the International Symposium on North Pacific Flatfish. Alaska Sea Grant College Program Report No. 95-04, University of Alaska Fairbanks.
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1996. Application of a one-dimensional geostatistical procedure to fisheries acoustic surveys of Alaskan pollock.
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1996. Diets of the important groundfish in the Aleutian
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AFSC Processed Reports for 1996
CLAUSEN, D. M.
1996. Report to industry: 1993 triennial bottom trawl survey of the eastern Gulf of Alaska, July-August 1993, RV Miller Freeman cruise 93-09. ASFSC Processed Report 96-03, 77 p. Alaska Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, Auke Bay Laboratory, 1305 Glacier Highway, Juneau, AK 99801-8626.
LIVINGSTON, P. A., and Y. DEREYNIER.
1996. Groundfish food habits and predation on commercially important prey species in the eastern Bering Sea from 1990 to 1992. AFSC Processed Report. 96-04. 214 p. Alaska Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 Sand Point Way NE, Seattle, WA 98115-0070.
PORTER, S. M., and G. H. THEILACKER
1996. Larval walleye pollock, Theragra chalcogramma, rearing techniques used at the Alaska Fisheries Science Center, Seattle, Washington. AFSC Processed Report. 96-06. 26 p. Alaska Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 Sand Point Way NE, Seattle, WA 98115-0070.
STARK, J. W.
1996. Report to industry: Fishing log for the 1984 bottom trawl survey of the Aleutian Islands. AFSC Processed Report 96-02, 122 p. Alaska Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 Sand Point Way NE, Seattle, WA 98115-0070.
STEVENS, B. G., J. A. HAAGA, and R. A. MACINTOSH.
1996. Report to industry on the 1995 eastern Bering Sea crab survey. AFSC Processed Report 96-01, 51 p. Alaska Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 Sand Point Way NE, Seattle, WA 98115-0070.
WALTERS, G. A. (Compiler).
1996. 1992 Bottom trawl survey of the eastern Bering Sea continental shelf. AFSC Processed Report. 96-05. 164 p. Alaska Fish. Sci. Cent., Natl. Mar. Fish. Serv., NOAA, 7600 Sand Point Way NE, Seattle, WA 98115-0079.
SAFEs ** Not to be cited **
CLAUSEN, D. M., and J. HEIFETZ.
1996. Pelagic shelf rockfish. In Stock assessment and fishery evaluation report for the groundfish resources of the Gulf of Alaska, p. 271-288. North Pacific Fishery Management Council, 605 W 4th Avenue, Suite 306, Anchorage, AK 99501.
DORN, M. W. 1996. Status of the coastal Pacific whiting resource in 1996. In Pacific Fishery Management Council, Status of the Pacific Coast groundfish fishery through 1996 and recommended acceptable biological catches in 1997, p. A1-A76. (Document prepared for the Council and its advisory entities.) Pacific Fishery Management Council, Suite 224, 2130 SW Fifth Ave., Portland, OR 97201.
FUJIOKA, J. T., M. F. SIGLER, and S. A. LOWE.
1996. Sablefish. In Stock assessment and fishery evaluation report for the groundfish resources of the Gulf of Alaska, p. 189-228. North Pacific Fishery Management Council, 605 W 4th Avenue, Suite 306, Anchorage, AK 99510.
HEIFETZ, J., J. N. IANELLI, and D. M. CLAUSEN.
1996. Slope rockfish. In Stock assessment and fishery evaluation report for the groundfish resources of the Gulf of Alaska, p. 229-269. North Pacific Fishery Management Council, 605 W 4th Avenue, Suite 306, Anchorage, AK 99510.
THOMPSON, G. G., and M. W. DORN.
1996. Pacific cod. In Plan Team for Groundfish Fisheries of the Bering Sea/Aleutian Islands (editor), Stock assessment and fishery evaluation report for the groundfish resources of the Bering Sea/Aleutian Islands region as projected for 1997, p. 47-75. North Pacific Fishery Management Council, 605 W. 4th Avenue Suite 306, Anchorage, AK 99501.
THOMPSON, G. G., H. H. ZENGER, and M. W. DORN.
1996. Pacific cod. In Plan Team for Groundfish Fisheries of the Gulf of Alaska (editor), Stock assessment and fishery evaluation report for the groundfish resources of the Gulf of Alaska as projected for 1997, p. 93-126. North Pacific Fishery Management Council, 605 W. 4th Avenue Suite 306, Anchorage, AK 99501.