Comparison of ecosystem models of the Newfoundland and Labrador Shelf and Grand Banks

Wudrick, Alannah (2023) Comparison of ecosystem models of the Newfoundland and Labrador Shelf and Grand Banks. Masters thesis, Memorial University of Newfoundland.

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Abstract

Ecosystem models are tools that can provide strategic ecosystem-based fisheries management (EBFM) advice by accounting for the influence of environmental drivers and food-web interactions on fish stocks. Ecopath with Ecosim (EwE) is an ecosystem modelling platform that uses a mass-balance approach to estimate ecosystem dynamics. Existing EwE models cover the Newfoundland & Labrador Shelf and Grand Banks for 1985-1987 and 2013-2015 time periods, representing ecologically significant time periods for the region. To provide higher spatial resolution to the existing models, I separated the single model area into two for the Newfoundland & Labrador Shelf and the Grand Banks and updated the models for the 2018-2020 time period. Evidence of a strong bottom-up influence from environmental drivers demonstrated that the two model regions are distinct in ecosystem structure and function, with variable temporal dynamics. Comparisons of the system across all three time periods provided insight into ecosystem dynamics. Primary/secondary production had increased since 2013-2015 in both areas, as well as groundfish abundance, but neither were above pre-groundfish collapse (before the early 1990’s) levels. Species composition and biomass was noticeably different between the northern and southern regions, as well as catch composition. Forage fish biomass did not show signs of recovery in either system, and may play key roles in predicting outcomes for the system in the near future.

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