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Shifts in the distributions of organisms due to large-scale changes in Pacific coast oceanographic currents have been investigated for many years (Radovich 1961; Parrish et al. 1981; Chelton et al. 1982; Roesler and Chelton 1987). Changes in currents are evidenced by measurements of physical factors such as temperature, salinity, nutrients, and sea level, and correlated to distribution and abundance of dependent organisms such as phytoplankton, invertebrates, and fish. Radovich (1961) described temperature as an important factor in distributions of numerous marine fishes off the Pacific coast of North America during the 1957-59 ENSO.
The 1957-59 and 1982-83 ENSO events have been described as among the major ENSO events in this century (Cannon et al. 1985; Squire 1987; Dayton and Tegner 1989). ENSO events are characterized by unusually warm water temperatures, disruption of nearshore upwelling, and subsequent decreases in primary and secondary production (Radovich 1961; Roughgarden et al. 1988; Dayton and Tegner 1989). Radovich (1961) described incidents of fish and invertebrates north of their usual ranges during the 1957-59 ENSO. The take of southern species of fish and invertebrates north of their usual ranges during the 1982-83 ENSO was qualitatively described for the state of Washington by Schoener and Fluharty (1985). Klingbeil et al. (1984) described changes in catch and northward shifts of southern species during 1983 in the commercial and recreational fisheries off central and southern California. Squire (1987) examined average "catch temperature" for recreationally important pelagic southern species determined from non-ENSO periods and, based on 1983 sea surface temperatures, predicted their northward distributions during that year. He used qualitative reports of catches from Alaska, Washington, Oregon, and California to support his hypothesized distributional changes.
Evidence for changes in distributions of fish species is dependent on collections made during research cruises or on samples from the catches of commercial or recreational fisheries (Radovich 1961; Klingbeil et al. 1984). The 1980-86 MRFSS data span the period of the 1982-83 ENSO with a random survey of recreational fishery catch composition. Distribution maps made from the data track variations in occurrence (percent of sampled catch, by district) of recreationally important species before, during, and after the 1982-83 ENSO. Examining the maps for all species sampled, we identified the species whose occurrence changed during the 1982-83 ENSO, and compared the changes to those reported during the 1957-59 ENSO.
We found 28 species with differences in distribution that may have been related to the 1982-83 ENSO (Table 11). Ten of those species, all of which are pelagic (Miller and Lea 1972; Feder et al. 1974), showed obvious northward shifts in occurrence during one or more years of the ENSO. The 10 species consisted of eight scombrids (albacore, bigeye tuna, bluefin tuna, bullet mackerel, Pacific bonito, Pacific mackerel, skipjack, yellowfin tuna), one coryphaenid (dolphinfish) and one sphyraenid (California barracuda).
Of the eight scombrids, Pacific mackerel showed the greatest northward shift in occurrence during 1982-83. The range of Pacific mackerel is described as transpacific by Miller and Lea (1972). Pacific mackerel in the Mendocino/Sonoma catch increased from nothing in 1981 to 1.8% of the total catch in 1982. In 1983 and 1984 Pacific mackerel represented about 1% of the central Oregon recreational catch. By 1986 Pacific mackerel were no longer taken north of the San Francisco district (Figure 72).
Pacific mackerel in northern and central California were smaller than in southern California (Figure 73). The modal progression of a cohort was seen from 1984 to 1986 in the northern and central California catch and also in the southern California catch (Figure 73). During the three years, average length increased from 234 mm to 252 mm in northern and central California, and from 297 to 323 mm in southern California.
A strong 1981 year-class dominated southern California commercial landings of Pacific mackerel in 1985, based on otolith age-at-size data (CDFG unpublished data). In the 1980-86 MRFSS data, dominant modes are apparent in the length-frequency distributions for southern and for northern and central California (Figure 73). Assuming mode A represents the 1981 year-class, a comparable mode was not present in northern and central California. Mode B to the north may represent younger fish that grew more slowly than expected from the Von Bertalanffy growth equation published by Knaggs and Parrish (1973). Mode B moved from 200 mm to 250 mm over a 4-year period from 1983 to 1986. Knaggs and Parrish (1973) found 1-year-old fish that were 273 mm long growing to 358 mm in four years. In the absence of age-at-size data, we can only speculate that either growth rates were markedly depressed or a series of young of the year were taken in the north. Klingbeil et al. (1984) reported a commercial landings shift northward to the Monterey area during 1982 and 1983, with 10% of the 1983 commercial landings in the Monterey area. The 1983 Monterey landings represent the largest landings of Pacific mackerel from that port area since the inception of the fishery five decades previously. Schoener and Fluharty (1985) reported increased abundance in 1983 from catches off Washington and in Puget Sound. Northward shift of Pacific mackerel was not noted during the 1957-59 ENSO by Radovich (1961). The lack of a shift may reflect low stock biomass during 1957-59, estimated at one-third the 1982-83 biomass (MacCall et al. 1985).
Bullet mackerel and albacore persisted to the north into 1986 following the ENSO. Bullet mackerel were caught in southern California in 1983-86 (Figure 72). Their northernmost and peak occurrence (0.74%) was in the Santa Barbara/Ventura district in 1984. Radovich (1961) described the range of the species as common off Mexico and Central America, with one fish collected off Los Coronados Islands in 1957 and 40 collected between Santa Catalina Island and San Clemente Island in 1959.
Northward catch of albacore was first apparent in 1982 (Figure 72). Catches persisted off Santa Cruz through San Luis Obispo counties through 1986. Klingbeil et al. (1984) reported albacore taken in Monterey Bay in September 1983; they were not found by the MRFSS (Figure 73). Schoener and Fluharty (1985) described increases in albacore landings off Washington following the 1957-58 ENSO and in 1983. Radovich (1961) described the presence of albacore as clearly related to ocean temperature and available inshore farther to the north during the 1931, 1957, and 1958 warm-water years.
Pacific bonito displayed a pronounced but transitory shift north of Point Conception in 1982-84 (Figure 72). In 1983, they were caught as far north as the Del Norte/Humboldt district. Radovich (1961) described the range of Pacific bonito as uncommon north of Point Conception until numerous specimens were found off the Farallon Islands and northwest of Eureka during 1957. Klingbeil et al. (1984) noted an increased northward occurrence in recreational fisheries starting in September 1982. The increase extended as far north as Crescent City by fall 1983. Schoener and Fluharty (1985) described Pacific bonito as more abundant than usual off Washington in 1983.
In 1983, skipjack tuna and yellowfin tuna both showed increased occurrence northward to the Santa Barbara/Ventura district (Figure 74). In 1984, skipjack tuna continued to be taken at reduced levels as far north as the Santa Barbara/Ventura district, while yellowfin tuna were taken only off Orange County. Klingbeil et al (1984) reported recreational catches of both species as far north as Ventura County in August 1983. Radovich (1961) described skipjack tuna as uncommon in southern California and rare north of Point Conception. During the 1957-59 ENSO, skipjack tuna were reported to be numerous as far north as Cape Blanco, Oregon and were commonly taken off southern California in 1957 (Radovich 1961).
Bigeye tuna were first taken off San Diego County in 1982 (0.78%) and as far north as Orange County in 1983 (Figure 74). Radovich (1961) reported the first bigeye tuna collected in California in 1959 and a range extension to Iron Springs, Washington in the same year. Klingbeil et al. (1984) reported the first landing of bigeye tuna off San Diego in July 1983, with 1700 fish reported on CPFVs from August through September of 1983.
Bluefin tuna were taken off San Diego County in 1983 and as far north as Santa Barbara/Ventura in 1984 (Figure 74). Klingbeil et al (1984) reported commercial catches of bluefin tuna in southern California during 1983. Radovich (1961) reported a bluefin tuna taken near Kodiak, Alaska in 1958.
Dolphinfish were available off Orange and San Diego counties in 1982 and 1983 at low levels of occurrence (0.05% to 0.3%) (Figure 75). Radovich (1961) described the species' distribution as worldwide in warm seas. He also reported numerous collections off San Diego and the Farallon Islands in California, and off Grays Harbor, Washington in 1957. In August through September 1983, 997 dolphin were reported taken by CPFVs off southern California (Klingbeil et al. 1984).
California barracuda showed the least quantitative shift to the north of the 10 species. The species was described as nearshore pelagic by Feder et al. (1974). In 1982, occurrence was low (0.03%) as far north as Del Norte/Humboldt (Figure 75). Low occurrence (0.01%) persisted in Santa Cruz/Monterey during 1983 and 1984. Klingbeil et al. (1984) reported recreational fishery take of barracuda off central California in 1983. Radovich (1961) reported numerous catches off British Columbia in 1958.
Earlier in this bulletin we examined distributions of 16 rockfishes, eight surfperches, and lingcod in 1980-86 (Figures 18-21, 42, and 58-60). None of those species showed clear evidence of latitudinal displacement during the 1982-83 ENSO. However, three rockfishes (chilipepper, widow rockfish, and greenstriped rockfish) and two surfperches (redtail surfperch and striped seaperch) did show interannual shifts in occurrence during or after the ENSO that were not clearly related to the ENSO (Table 11). Chilipepper displayed an increase in occurrence in San Luis Obispo through Mendocino counties in 1985 and 1986 (Figure 19); the strong 1984 year-class was present during that period (Rogers and Bence, 1992). Widow rockfish were caught by recreational fisheries off Oregon from 1983 through 1986; none were seen there before 1983 (Figure 18). Greenstriped rockfish were not found in Oregon until after 1983 (Figure 21). Occurrence of redtail surfperch and striped seaperch decreased off Oregon in 1982 relative to the other five years investigated (Figure 58). The decreases may have been related to the warmwater event, but did not constitute latitudinal displacement from the species' normal ranges (Table 11). During the 1957-59 ENSO, only one rockfish species (greenspotted rockfish) and no surfperch showed evidence of northward shift (Radovich 1961). Greenspotted rockfish distribution showed no evidence of northward shift during the 1982-83 ENSO (Figure 19). Thus available data suggest that rockfish and surfperch do not undergo obvious latitudinal shifts in distribution during warmwater periods.
In addition to the three rockfishes and two surfperches, 13 other species showed increases or decreases in occurrence during 1982, 1983, or 1984 that may have reflected effects of the ENSO (Table 11). The differences were not pronounced enough north or south to be described as latitudinal shifts in distribution. The 13 species included six species of bottom fish (barred sand bass, California sheephead, ocean whitefish, petrale sole, sand sole, and spiny dogfish), four nearshore species (black croaker, opaleye, señorita, and shovelnose guitarfish), and three pelagic species (Pacific hake, yellowtail, and white seabass) (Appendix G). Radovich (1961) reported northward shifts during the 1957-59 ENSO for three of those species: California sheephead, white seabass, and ocean whitefish (Table 11). Squire (1987) reported catches of yellowtail off central California and the catch of a single yellowtail in 1983 off Port Orford, Oregon. The MRFSS did not sample any yellowtail north of Point Conception during the ENSO.
White seabass were frequently taken north of their typical range during the 1957-58 ENSO (Radovich 1961); they were typically uncommon north of Point Conception, but were abundant off San Francisco in 1958 and numerous off Monterey in 1959. Catches were reported off Oregon, Alaska, and British Columbia in 1957 and 1958. The range of white seabass has contracted with a decrease in population from the 1950s to the 1980s. CPFV catches in southern California in the 1980s were only 3% of what they were from 1947-59 (Vojkovich 1992). Squire (1987) described isolated catches off California and Oregon in 1983. The MRFSS data show increased occurrence off southern California only in 1982 and low occurrence (0.01%) off Santa Cruz/Monterey, also in 1982 (Appendix G).
The northward increases in occurrence for the 10 pelagic species should be compared cautiously to the 1957-59 ENSO reports by Radovich (1961). The latitudinal shifts described here are based on MRFSS data that 1) quantify gross movement as a percentage of all species taken by district, 2) consider only the take of recreational fisheries, mainly from inshore areas (except in southern California), and 3) did not record depth of capture. The MRFSS is a random survey targeting broad geographic areas and offers a coarse level of resolution by district and year. The movements north or south described by Radovich (1961) and Squire (1987) often represented rare events targeted by scientists focused on identifying an anomaly. In general, ranges reported in the literature for marine fish reflect a similar focus on unusual events and say little about actual quantitative distribution of a species. Rarely are resources devoted to conduct species distribution and abundance surveys. An example of such were the two federal rockfish surveys of 1977 and 1980 (Gunderson and Sample 1980; Dark et al. 1983). The MRFSS data fall short of quantifying true abundance but do quantify relative abundance in the sampled catch.
Recreational fisheries in central and northern California and Oregon are generally concentrated nearshore due to weather, the narrow continental shelf, and types of vessels used. Recreational fisheries in southern California access both nearshore and offshore areas, targeting both groundfish and pelagic species. In northern and central California, offshore commercial troll fisheries target salmon and occasionally albacore. Most recreational boat fisheries target bottomfish or salmon. Radovich (1961) reported landings from both recreational and commercial vessels in the north, with many of the pelagic species noted well offshore and out of the range of recreational boats sampled by the MRFSS.
Distance offshore and depth of fishing should be included in future marine recreational surveys for improved quantification of species distributions during ENSO events. Our findings on the status of rockfish reveal a shift to deep- water rockfish species between 1958-62 and 1980-86 by PRB and CPFV anglers that suggests a need for caution when evaluating species' distributions as an index of ENSO effects. Apparent changes in distribution could also reflect targeting shifts to deep-water species.
Squire (1987) hypothesized shifts north of Point Conception of the southern pelagic species yellowtail, California barracuda, Pacific bonito, Pacific mackerel, yellowfin tuna, striped marlin, and white seabass. He suggested that as sea surface temperatures increased to the north, those species would follow their typical "mean catch temperature" ranges into northern waters. Squire (1987) suggested that Pacific bonito, with the lowest "low mean catch temperature" (LMCT) (12.2° C) would exhibit a further shift to the north during 1983 than white sea bass, California barracuda, Pacific mackerel, and yellowtail (with LMCTs of 13.3° C, 13.9° C, 13.9° C, and 13.9° C respectively). Our MRFSS data indicate that the northward populations shifts, within Oregon and California, were led by Pacific mackerel, followed by Pacific bonito, and yellowfin tuna. California barracuda and white seabass showed little evidence of northward shift. Ally and Miller (1992) suggested that declines in California barracuda populations since the 1957-59 ENSO account for the less pronounced northward movement observed during what they described as the equally intense 1982-83 ENSO. We suggest the same effect for white seabass, based on declines in abundance reported by Vojkovich (1992).
All 10 of the species we identified as dislocated to the north during the 1982-83 ENSO event were also named by Radovich (1961) for the 1957-59 ENSO. The fact that Radovich's (1961) list of dislocated species (49 fishes) was larger then ours does not imply that the 1957-59 ENSO had a greater effect on species distributions. Radovich (1961) utilized both inshore and offshore sport and commercial samples over a wide range from California to Alaska. Our study relied on samples only from sportfish anglers in California and Oregon. The Radovich (1961) study counted rare events (51% of the species he listed were based on a single observation) while our graphical analysis included only species with multiple observations. Added factors such as decreases in population density for white seabass and California barracuda or population recovery for Pacific mackerel obscure or exaggerate apparent shifts in distribution. Hopefully, surveys such as MRFSS will be active during future ENSO events, providing a basis for quantitative comparison of pelagic species dislocations to our results. Ultimately such comparisons could provide a basis for classifying the relative magnitude of ENSO impacts on pelagic fishes.