Alternative models of climatic effects on sockeye salmon, Oncorhynchus nerka, productivity in Bristol Bay, Alaska, and the Fraser River, British Columbia

Abstract

We compare alternative models of sockeye salmon, Oncorhynchus nerka, productivity (returns per spawner) using more than 30 years of catch and escapement data for Bristol Bay, Alaska, and the Fraser River, British Columbia. The models examined include several alternative forms of models that incorporate climatic influences as well as models not based on climate. For most stocks, a stationary stock‐recruitment relationship explains very little of the interannual variation in productivity. In Bristol Bay, productivity covaries among stocks and appears to be strongly related to fluctuations in climate. The best model for Bristol Bay sockeye involved a change in the 1970s in the parameters of the Ricker stock‐recruitment curve; the stocks generally became more productive. In contrast, none of the models of Fraser River stocks that we examined explained much of the variability in their productivity.

Historical trends in productivity of 120 Pacific pink, chum, and sockeye salmon stocks reconstructed by using a Kalman filter

“…While it is possible to have either the a or b parameter (or both) vary over time, we limited our analysis to a timevarying a t for three reasons. First, Adkison et al (1996) found that for Bristol Bay sockeye stocks, the a parameter tended to change much more over time than the b parameter. Second, assuming that the Ricker b parameter (but not a) was time-varying would imply that substantial changes in log e (R/S) would occur only when spawner abundance was large (i.e., a change in the level of density-dependent feedback).…”

Nonlinear dynamics in ecosystem response to climatic change: Case studies and policy implications

“…A marine climate shift in the North Pacific Ocean and Bering Sea in the 1970s has been well documented in the literature (Pearcy, 1992;Rogers and Ruggerone, 1993;Mantua et al, 1997). Ocean climate and oceanlinked terrestrial climate affect all phases of Pacific salmon life history in the north Pacific region and play a significant role in salmon production on interannual, as well as interdecadal, time scales (Adkinson et al, 1996;Downton and Miller, 1998). Mortality and maturation of salmon appear to be linked to broadscale fluctuations in ocean climate (Beamish and Bouillon, 1993); however, more localized upwelling circulation patterns can affect local productivity and salmon growth at sea (Fisher and Pearcy, 1988;Kope and Botsford, 1990).…”

Comparison of Akaike information criterion (AIC) and Bayesian information criterion (BIC) in selection of stock–recruitment relationships

“…AIC has the advantage of testing the significance of the differences between the functions of different model specifications (Akaike, 1973). Sakamoto et al (1986) describe an alternative to the AIC, called the BIC (Adkison et al, 1996), which is also a tool of selecting the best model. The purpose of this paper is to test and compare the ability of AIC and BIC in selecting the true SR models by simulated SR data generated by the six SR models.…”