Date of Award

Spring 2025

Project Type

Dissertation

Program or Major

Biological Sciences

Degree Name

Doctor of Philosophy

First Advisor

Nathan B Furey

Second Advisor

Easton White

Third Advisor

Rebecca Rowe

Abstract

Marine organisms are confronted with warming waters due to climate change requiring species to exhibit responses to persist. For many fish, these responses have included range shifts to cooler waters, but are species-specific which may create further disruption through trophic mismatches. To identify potential mismatches and estimate their implications for the quality of consumption within major predators, analyses of predator stomach contents were integrated with reviews of organismal energetics and physiological parameter values. The energy density of prey that is consumed dictates the consequences of consumption, so having data expands general understanding of diet. To that end, published records (n = 134 sources) of energy density were integrated into a single database containing 2018 taxa. Diet collections were conducted by the Northeast Fisheries Science Center as part of the Spring and Fall Bottom Trawl Survey from the Northeast US Continental Shelf Large Marine Ecosystem (NEUS) community of fishes (n = 41 predator species). Individual diets (n = 369,540 diets) spanning decades (1973-2019) were used for a temporal analysis of feeding guild assignment, multivariate guild interrelatedness, and individual predator diet quality. Together, community analyses revealed a high degree of consistency in feeding behaviors as predators largely (>87%) retained guild assignments, but declining inter-guild dispersion (p = 0.010) suggested that the community is being compressed. Individual predators by season showed similar patterns of compression based on diet breadth losses (83.0% of predators) which may have driven the decline in relative consumption and increased stomach emptiness further observed in many predators (79.6% and 44.0%, respectively). Pairing these observations of diet with the energy density database revealed that average diet energy densities were quite stable (no meaningful change for 61.0% of predators), thereby indicating no compensatory prey selectivity to prevent losses in absolute and relative energy consumption (54.2% and 66.1% of predators declining, respectively). Post-hoc analyses revealed that benthic-oriented predators experienced the most rapid decline on average, especially those from the Polychaete/Amphipod eaters guild, such as witch flounder or haddock. A comparison of species characteristics to parameters of bioenergetics models (n = 101 models) revealed them to be highly variable across taxa (n = 70 species), depending on the ecology of the species. Bioenergetic models also were used to calculated temperature windows across which growth occurs and a novel relative index of resilience. Whereas temperature windows varied widely between species (range 9 – 40°C), a relative index of resilience suggests that high sensitivity to warming was common 82.8% of models). My results suggest that diet quality for a broad community of predators has declined over the past ~50 years due to an apparent lack of feeding adaptiveness. The consequences of these declines may result in an acceleration of distribution shifts as consumption limitations are spatially variable due to and resulting in predator-prey spatial mismatch. These results indicate that the ability of predators to maintain trophic connections threatens marine ecosystems above and beyond warming waters alone and is important to consider to effectively manage fisheries experiencing such changes.

Download

Share

COinS