Abstract
AbstractWaters of the northern Gulf of Alaska around Kodiak Island once supported the world's largest fishery for the red king crab Paralithodes camtschaticus. Commercial fisheries began at low levels in the 1930s, increasing rapidly in the 1960s to a peak harvest of 42,800 metric tons in 1965. Stock abundance declined sharply in the late 1960s, moderated in the 1970s, and crashed in the early 1980s. A commercial fishery closure since 1983 has not resulted in stock recovery. To improve understanding of stock dynamics, we examined spawner–recruit (S‐R) relationships for the Kodiak red king crab stock. The shape of the S‐R relationship helps describe average stock productivity at different stock levels, thus relating directly to fishery management objectives. Due to limited female data, we used only male data and two currencies of male abundance as a proxy for spawners: either (1) all males greater than or equal to 125 mm carapace length (CL) or (2) legal males (≥145 mm CL). Due to age uncertainty, we considered lag times of 5 to 8 years between reproduction and recruitment. Residuals from fitting a standard Ricker model were strongly negative for brood years from the mid‐1970s to the mid‐1980s and positive from the early to mid‐1990s. A Ricker model with autocorrelated errors resulted in better fits with corrected Akaike's information criterion (AICc) values minimized for a 5‐year lag using all males. Among model configurations, estimates of peak production ranged from 2.0 to 3.4 million recruits from a range of 11.3 to 37.7 million males. A model separating the time series into three productivity periods corresponding to different ecological regimes further improved model fit. Although abundances of both spawners and recruits have been less than 1.0 million males since 1985, depensation at low stock sizes was not detected. Future analyses will examine the contribution of ecological and environmental factors to crab recruitment.
Highlights
IntroductionA model separating the time series into three productivity periods corresponding to different ecological regimes further improved model fit
Spawner abundance corresponding with peak recruitment ranged from 24.2 to 44.0 million crab if measured as legal males (!145 mm carapace length (CL)) or 42.4 to 81.3 million crab if measured as all males (!125 mm CL; Table 2)
Estimates of a and b were larger for legal-male models than for all-male models under similar lags and correlation configurations, the precision of the estimates was similar for a given configuration (Table 2)
Summary
A model separating the time series into three productivity periods corresponding to different ecological regimes further improved model fit Abundances of both spawners and recruits have been less than 1.0 million males since 1985, depensation at low stock sizes was not detected. The northern Gulf of Alaska near Kodiak Island (Figure 1) once supported the world’s largest fishery for the red king crab Paralithodes camtschaticus Commercial harvests from this area first occurred in the 1930s, annual harvests were relatively minor until the early 1960s when improved market conditions, changes in vessel technology, and the introduction of vessels designed to harvest red king crab resulted in a rapid increase in fishing effort and catch (Figure 2; Gray et al 1965; Spalinger 1992).
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