PhD defence Bass Dye

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Bass Dye (Marine Biology/NIOZ)

Promotor: Prof. B.D.H.K. Eriksson; copromotor: Dr A. van Leeuwen (NIOZ)

The heat is on

Yet various factors influence fish performance

A changing climate has triggered global environmental shifts, including biodiversity loss and altered species distributions. Rising sea temperatures pose a major challenge to ectothermic organisms, whose physiological processes depend on external conditions. However, species exhibit varied responses to warming waters. Some relocate to new habitats, moving into deeper waters or migrating northward, while others face habitat limitations that increase their vulnerability to climate-induced changes. Additionally, food availability shapes species’ responses and performance, particularly in dynamic coastal ecosystems where environmental and anthropogenic changes are often most pronounced.

This thesis explores how temperature and resource availability influence physiological performance and population dynamics of fish. Experimental studies suggest that the increasing presence of five-bearded rockling in the Wadden Sea may be linked to larger abundance of mussel and oyster reefs, highlighting the importance of structural habitat. Similarly, grey mullet consistently prefers warm waters across varying salinities, suggesting that rising temperatures in the Wadden Sea will continue to support this species. Using a bioenergetics model, I studied size-specific predictions of life history traits across different temperatures and resource levels for five marine species. This analysis demonstrates that even small temperature increases impact performance, though resource availability remains the dominant factor. Likewise, an analysis of European seabass population dynamics indicates that while warming waters can enhance performance, resource abundance is the primary driver to changing regulation of population dynamics. This thesis highlights the need for a holistic approach to assessing impacts of rising temperature, integrating empirical research with modeling across individual, population, and ecosystem levels.

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