The red abalone sport resource appears to be doing well on the Sonoma-Mendocino coast, while the picture in the rest of the state appears bleak at best. A soon-to-be-completed report on the status of red abalone stocks in northern and central California gleans the results of low-tide field surveys taken from 1975 to 1994 at 12 locations in Humboldt, Mendocino, Sonoma, and San Mateo counties, and also summarizes estimates of total effort and take from random telephone surveys in 1985-89.
The telephone surveys, in which over 60,000 northern and central California households where contacted, show that a large sport fishery now exists in northern California. Divers and shorepickers took an annual average of 2,000,000 pounds in 1985-89, and diving take has increased ten-fold since 1960 (Figure 1).
In the low-tide field surveys, 13,500 divers and 18,643 shore pickers were interviewed, and over 40,000 abalone were examined and measured. The 12 field locations surveyed were, from north to south, Shelter Cove in Humboldt County; Hardy Creek, Mackerricher State Park, the Noyo launch ramp, Chapman,Van Damme State Park, Albion River launch ramp, Arena Cove, and Moat Creek in Mendocino County; Salt Point and Pedotti State Park in Sonoma County; and Fitzgerald Reserve through Franklyn Point in San Mateo County.
Abalone catch rates have remained high in Mendocino and Sonoma counties, averaging about 3 abalone per day. Catch rates were slightly lower at Shelter Cove, averaging just under 3 per day. Catch rates were lowest in San Mateo County, averaging less then 2 per day.
Abalone average sizes varied by location with San Mateo producing the smallest diver-caught abalone (7.5 inches), and Point Arena producing the largest (8.0 inches). The results are not surprising considering the low densities of abalone at Fitzgerald (Kelp Forest No. 2), where the remaining abalone stocks are less than 10% of those in Sonoma and Mendocino counties. The low densities at Fitzgerald appear to be the result of combined sport and commercial fisheries, which have eliminated almost all abalone from waters deeper than 30 feet and continue to intensively harvest the remaining stocks in shallower water.
At Van Damme State Park, where our sampling has been most consistent, average size taken by divers has increased in recent years, an unusual trend (Figure 2). Starting about 1987 larger abalone started showing up, especially in the diver catch (Figure 2), but also among shorepickers. The same trend is evident at other sites in Mendocino and Sonoma counties. Annual scuba surveys , conducted at Van Damme since 1986 , show an influx of recruitment (young abalone) beginning in 1989. Growth rates of the new "recruits" have been unusually high compared to growth rates measured in the 1970s. What's going on here?
One possible explanation is increased use of boats, which allow divers to go further to get larger abalone. Indeed our data from all sites show that boat divers that went further took larger abalone (Figure 3). Boat divers who traveled the furthest (about 5 miles) averaged 8.5 inch abalone while divers who ventured less than a mile averaged 7.7 inch abalone. This however does not explain increased sizes among shorepickers and from sampling locations where boat divers were not surveyed.
A more likely explanation has to do with the large scale commercial removal of a major abalone competitor, the red sea urchin. Urchin are known from studies in southern California and Australia to compete with abalone for space and food. A commercial fishery for red urchin in northern California started in 1985, peaked in 1988 (35 million pounds harvested!), and declined thereafter (5 million pounds landed in 1993). Pete Kalvass, a CDFG biologist here in Fort Bragg, estimates that some 111 million pounds of a 165 million original total (67%) have been mined out over the past 8 year period! The results of have been dramatic. CDFG aerial infrared surveys show that kelp surface areas have increased at Van Damme, paralleling this decline in urchin biomass.Although the apparent decline in urchin stocks is bad news for the urchin fishery, it may have helped abalone populations and the sport abalone fishery. The only potential bad news for the abalone resource has been a concurrent increase in poaching since 1985 (see Poached Abalone) that has apparently followed the urchin fleet north from southern California. Poaching of deep water stocks may threaten the northern abalone populations since our research suggests deep water populations are what sustain a sport fishery that removes almost two million pounds annually. Deeper water animals are available to spawn and move in as the shallow water animals are removed by shorepickers and divers. In central and southern California where abalone are subjected to commercial take, sport use of SCUBA, and expanding sea otter populations, the stocks have crashed.-KK