Identifying prey traits to predict for predator diet shifts under climate change in albacore tuna

Natasha Hardy, University of Alberta, Edmonton, AB, Canada, Cindy Matuch, Hopkins Marine Station of Stanford University, Monterey, CA, United States, Elliott L. Hazen, NOAA Southwest Fisheries Science Center, Environmental Research Division, Monterey, United States, Michael Jacox, University of California-Santa Cruz, San Francisco, CA, United States, Steven J. Bograd, National Oceanic and Atmospheric Administration, Southwest Fisheries Science Center, Monterey, United States, Larry Crowder, Hopkins Marine Station, Department of Biology, Pacific Grove, CA, United States and Stephanie Green, University of Alberta, Biological Sciences, Edmonton, AB, Canada
Abstract:
Climate change is driving shifts in marine species to maintain their preferred habitat, whilst decoupling food web components and resulting in fisheries production shifting across jurisdictional boundaries. Here, we investigate the role of functional trait metrics in predicting predator-prey relationships across geographies and climate-induced shifts of highly-migratory pelagic predators. Albacore tuna (Thunnus alalunga) are widely distributed throughout the temperate regions of the world’s oceans and have a highly diverse diet. In a global meta-analysis, we identified over 400 unique prey taxa identified in the diets of albacore tuna from historical through to contemporary analyses of their diets. We therefore test the relevance of trait-based frameworks for analyzing patterns in the diets of albacore tunas using a fourth-corner modelling approach, in order to identify significant ecological predictors for shifts in predator diets beyond descriptive or taxonomic methods. Prey species traits identified with strong potential to influence the predation process for tunas include prey morphologies, habitat association, aggregating as well as diel and seasonal migratory behaviour. We then apply these identified trait-level rather than taxonomic indicators to model the prey selection process in a case study for albacore tuna in NE Pacific food webs under past climatic conditions. We highlight how this approach could be used to forecast the strength of predator-prey interactions as species’ ranges shift under climate change in the NE Pacific. Analytical tools that incorporate predictive traits to evaluate the effect of predation on species abundance will add salient and cost-effective information to existing species distribution and ecosystem-based models. Our team welcomes international collaborations on tuna diet data to produce predictive tools for predator-prey interactions across jurisdictional boundaries and gradients of environmental change.
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