Date of Award

5-2026

Rights

© 2026 Jessica B. Maguire

Document Type

Thesis

Degree Name

Master of Science in Marine Sciences

Department

Marine Science

First Advisor

Will Kochtitzky

Second Advisor

Gwangseok R. Yoon

Third Advisor

Ben Tupper

Abstract

Rapid ocean warming in the Gulf of Maine is driving pronounced shifts in the distribution and composition of marine species, creating increasing challenges for fisheries management. Predicting these changes requires not only identifying where suitable habitat is shifting but also understanding the physiological mechanisms that determine whether species can occupy and persist in newly available environments.

Through this thesis, we aimed to better understand the environmental and physiological drivers of large-scale species distribution shifts in the Gulf of Maine. Studies were developed to (1) model the effects of environmental drivers on the current and projected distributions of commercially important fish species in the Gulf of Maine (Chapter 1), and (2) examine temperature-driven metabolic tradeoffs in growth and energy reserves that may underlie large-scale distribution shifts in marine fishes (Chapter 2).

The first experimental chapter utilized generalized additive models parameterized with long-term bottom trawl survey data (2000–2020) to quantify species–environment relationships for ten commercially and recreationally important taxa and to project habitat suitability under multiple climate scenarios (SSP1-1.9, SSP2-4.5, SSP5-8.5). Projections indicate contraction of suitable habitat for cold-affiliated species, including Atlantic cod, haddock, and pollock, alongside poleward and offshore expansion of warm-adapted and generalist species such as black sea bass, silver hake, and Jonah crab. These shifts frequently cross ecosystem-based fisheries management boundaries, suggesting increasing spatial mismatches between species distributions and existing management

frameworks. The second experimental chapter used controlled temperature exposures to simulate the poleward expansion of black sea bass (Centropristis striata) into northern Gulf of Maine thermal regimes. Juvenile black sea bass performed well across temperatures representative of summer conditions, exhibiting increased somatic growth at elevated temperatures and relatively stable digestive capacity. However, warmer conditions also resulted in reduced hepatosomatic index, indicating a trade-off between growth and energy storage. In contrast, higher energy reserves at cooler temperatures suggest that energy allocation strategies may shift across thermal environments, with implications for overwinter survival and seasonal residency. Together, these results demonstrate that climate-driven redistribution is governed by temperature-dependent physiological trade-offs that shape species performance, persistence, and ecological interactions. Integrating predictive habitat models with organismal physiology provides a mechanistic framework for anticipating species redistribution and supports the development of climate-ready fisheries management strategies in a rapidly warming ocean.

Comments

Master's Thesis

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