Title:

Retrospective dietary analyses of key benthic fishes of the Western Atlantic

The Gulf of Maine is a productive environment with great social, ecological, and commercial value, but which is experiencing community-wide changes due to climate change. As ocean temperatures rapidly rise there, many species are shifting poleward and/or offshore seeking preferred conditions. Due to species-specific shifts, there is a high potential for predator-prey interactions to change. Using the historical diet data collected by the National Marine Fisheries Service (1973-2019), we characterized feeding behaviors and identified changes in diet for a selection of 9 focal, benthic predators (e.g., Spiny Dogfish Squalus acanthias). We calculated traditional dietary metrics—breadth, frequency of emptiness, and relative consumption—across spatio-temporal gradients to observe when and where changes occur for species. Species were seen to exhibit inter-specific differences in diet type consistently across geographic regions and decades. Foraging strategies for predators were generally exhibited through trade-offs in dietary characteristics, such as a direct relationship between the mean prey size and the frequency of empty stomachs. These species-specific dietary niches identified were generally consistent with prior characterizations of feeding guilds, but some changes in diet composition were evident. Thus, distinguishing how sensitive different predators are to changing prey availability could inform management and conservation with future ecological changes.

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