Effects of water temperature and wind on year‐class success of Tanner crabs in Bristol Bay, Alaska

Abstract

We investigated five a priori hypotheses on factors affecting year‐class success of commercially exploited Tanner crabs, Chionoecetes bairdi, in Bristol Bay, Alaska, through correlation analysis and multiple regression modelling. Estimates of recruitment from Zheng et al.’s (1998; Can. Spec. Publ. Fish. Aquat. Sci. 125:97–105) length‐based analysis of assessment survey and commercial catch data were used to index year‐class strength. This work extends results of an earlier study (Rosenkranz et al., 1998; Alaska Fish. Res. Bull. 5:18–24), which reported positive correlations between Tanner crab year‐class size and north‐east (NE) winds during the spring larval period, by considering the effects of nondirectional wind speed, bottom and surface water temperature, and abundance of the potential predators sockeye salmon (Oncorhynchus nerka) and Pacific cod (Gadus macrocephalus). No relationships were found between year‐class size and mean wind speed or predator abundance, but positive correlations were found with bottom temperatures during gonadal development and egg incubation. Linear regression models with the independent variables NE wind and bottom temperature accounted for about half the variability in the year‐class strength index (r2=0.50 for males, r2=0.48 for females). Anomalously cold bottom temperatures may adversely affect the Tanner crab reproductive cycle, and NE winds may promote coastal upwelling while advecting larvae to regions of fine sediments favourable for survival upon settling. The role of Bering Sea oceanography on decadal‐scale variability in Tanner crab population dynamics could not be resolved with the relatively short (∼ two decades) time series of stock assessments.