Determining the impact of global warming on Atlantic salmon populations
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Date
2024
Authors
Rinaldo, Adrian
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University College Cork
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Abstract
Climate change poses a significant threat to anadromous fish species such as the Atlantic salmon (Salmo salar), whose life history is tightly coupled with environmental conditions in freshwater ecosystems. In this thesis, I investigate how rising river temperatures and other human-induced pressures reshapes juvenile growth, life-history scheduling, and demographic patterns in Atlantic salmon populations across Europe. Using a combination of long-term datasets, climate model projections, statistical modelling and individual-based models, I explore the phenotypic and demographic responses of salmon to changing thermal regimes and other environmental pressures.
My first study focuses on the Atlantic salmon population native to the Burrishoole catchment on the west coast of Ireland, using decades of climate and biological data to model the relationships between atmospheric conditions, water temperature, and growth in juvenile Atlantic salmon. Projections of future climate change suggests a shift towards earlier smoltification, with an increasing proportion of juveniles migrating as one-year-old smolts. These changes are expected to have a cascading effect throughout the life-cycle and ultimately impact the population dynamics of the Atlantic salmon population native to the Burrishoole catchment.
Expanding the spatial scope, my second study investigates temperature-dependent growth rates across 15 European populations using the modelling framework developed in my first study. The analysis indicates latitudinal differences in growth rates despite accounting for temperature differences using a degree-day approach. I find that population-specific growth rates are important for the accurate estimation of climate change impact on life-history scheduling, which underpins the importance of regional adaptations in shaping climate resilience.
My third study examines how gene flow from farm escaped Atlantic salmon alters growth responses and life-history timing in wild populations. Through common garden experiments and growth simulations, I demonstrate that fish with farm ancestry exhibits faster growth and earlier smoltification than their wild conspecifics, which may potentially reduce life-history diversity and increase vulnerability to climate change.
Finally, my fourth paper investigates the ecological implications of reproductive behaviour in Atlantic salmon, specifically the spatial clustering of offspring in redds. Using a spatially explicit, individual-based foraging model supported by empirical data, I show how early-life density-dependent mortality in clustered spatial distributions may be compensatory, which may entail better growth conditions and potentially higher smolt production compared to dispersed spatial distributions. This finding suggests that the protective spawning strategy which has evolved in salmonids of clustering eggs in gravel substrates rather than dispersing them is not ecologically disadvantageous.
Collectively, this thesis provides new insights into how climate change and other anthropogenic impacts may interact in the future to shape the biology of Atlantic salmon. By integrating long-term monitoring, climate projections, statistical models, it highlights the vulnerabilities of salmon populations in the face of climate change.
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Keywords
Atlantic salmon , Climate change , The Inter-Sectoral Impact Model Intercomparison Project , Life history , Individual-based modelling
Citation
Rinaldo, A. 2024. Determining the impact of global warming on Atlantic salmon populations. PhD Thesis, University College Cork.