Advancing ecosystem-based fisheries management on the Grand Banks of Newfoundland

Ruiz Díaz, Raquel (2025) Advancing ecosystem-based fisheries management on the Grand Banks of Newfoundland. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Traditional fisheries management has long operated within a single-species lens. Yet, the persistent degradation of marine ecosystems, loss of biodiversity, and the consequential decline in ecosystem services highlight the imperative to embrace new approaches to resource management. This thesis explores various methods to advance ecosystem-based fsheries management (EBFM) on the Grand Banks of Newfoundland (3LNO NAFO divisions), flling knowledge gaps on the impacts of climate change on snow crab, yellowtail founder and Atlantic cod biomass and distribution, and the role of forage species and top predators on the stability of the Grand Banks community. By using spatio-temporal models, which capture spatial and temporal correlations in data and account for species habitat preferences, I detected a northern shift in the average location of biomass for Atlantic cod, suggesting either a northward movement of the 3NO southern stock or a rapid recovery of the 2J3KL northern stock. In contrast, the centre of gravity of snow crab and yellowtail founder have remained relatively stable over time. I also developed new spring biomass indices for these species in the 3LNO divisions. I used species distribution models to forecast changes in focal species distribution and biomass by the end of the century. These models use bottom temperature data from three climate models (GFDL-ESM4, IPSL-CM6A-LR, and ACM) and three emissions scenarios (SSP1-2.6 and SSP3-7.0/SSP4-6.0) to force the projections. The fndings suggest that warming is expected to reduce the biomass of snow crab and yellowtail founder, while increasing the biomass of Atlantic cod, especially in the 3NO stock. Furthermore, I developed a size spectrum model to evaluate bottom-up versus top-down controls. My fndings indicate that Atlantic cod may play a more important role than forage fsh in the stability of the Grand Banks community. Overall, this thesis provides critical insights into the application of EBFM on the Grand Banks. It emphasizes the necessity for adaptive management strategies in response to climate-driven changes and highlights the importance of advanced modelling approaches to understanding complex ecological interactions.

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