Many multispecies models have assumed that prey density determines the per-capita predator consumption rates, following a functional response relationship. However, empirical evidence suggests that a predator’s diet can also be influenced by a variety of environmental factors, including interactions with other predators. Researchers in this study used diet and abundance data from the National Marine Fisheries Service (NMFS) bottom trawl surveys for three groundfish predators Pacific cod, Pacific halibut, and sablefish in the Gulf of Alaska to determine whether temperature or other species influence the consumption of walleye pollock.

Using an information-theoretic approach, researchers tested for relationships between walleye Pollock observed in predator stomachs and predator length, bottom temperature, prey availability (walleye Pollock catch per unit effort (CPUE) scaled by observed prey lengths), and CPUE of the three predators and arrowtooth flounder. Predator length was positively related to walleye Pollock presence and proportion of total diet mass in all predators. Increased temperatures negatively affected consumption of walleye Pollock by Pacific halibut, but not the other predators. Researchers found evidence for a number of inter-predator effects of co-occurring predators, both positive (facultative) and negative (competitive). Surprisingly, observed prey density was not statistically significant with respect to consumption for these predators, suggesting that trawls sample the environment far differently than walleye Pollock predators or species interactions are more complex than those used in previous multispecies models. These factors should be considered for future models contributing to ecosystem-based management.

Thompson, Kevin A., et al
Short Description: 
Research suggest predator interactions and temperature affect the consumption of Gulf of Alaska walleye pollock by three groundfish predators.
Product Number: 
Entry Date: 
Wednesday, August 26, 2015
11 pages
Size and Format: 
8.5 x 11 online
Additional authors: Selina S. Heppell and Grant G. Thompson
Source (Journal Article): 
Canadian Journal of Fisheries and Aquatic Sciences, 71(8), 1123-1133
DOI Number (Journal Article): 
Year of Publication: 
How to Order: 

Open access publication; free download