Patterns in Octopus Predation By Pacific Cod, Gadus macrocephalus , in the Eastern Bering Sea

Pacific cod appear to sample octopus more effectively than bottom-trawl stock assessment surveys conducted by the Alaska Fisheries Science Center. A departure from traditional methods, Pacific cod consumption estimates are used as a basis for estimating minimum biomass and mortality of the octopus complex in the Eastern Bering Sea/Aleutian Islands management area. These diet-based estimates are directly used to set the annual catch limit for octopus in the Bering Sea/Aleutian Islands. In this study we identify spatial and ontogenetic patterns in Pacific cod predation on octopus across the Eastern Bering Sea continental shelf using more than 30 years of annual stomach contents data. Regression between octopus body mass and keratinous mandible length is used to estimate initial octopus prey masses from stomach contents. The size composition of prey octopus is then compared with the composition reported from annual bottom-trawl surveys to examine possible size-selectivity bias between sampling methods.