Estimating abundance indices for NAFO Subarea 2 + Division 3K redfish via a spatiotemporal model

Fuller, Natalie (2023) Estimating abundance indices for NAFO Subarea 2 + Division 3K redfish via a spatiotemporal model. Masters thesis, Memorial University of Newfoundland.

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Abstract

Redfish (Sebastes spp.) are commercially important groundfish whose fisheries experienced some devastating collapses in the Northwest Atlantic of Canada. The stock on the Labrador Shelf (Northwest Atlantic Fisheries Organization Subarea 2 + Division 3K) is currently under a fishing moratorium but has experienced some recent population growth. Since there is currently no accepted assessment model for this stock, crucial decisions on when and how the fishery may reopen are determined by abundance indices. One big concern for this stock is the reliability of the abundance indices estimated from research surveys, especially with the partial and inconsistent survey coverage that has occurred over time. A possible solution for index standardization is via a spatiotemporal model, which utilizes spatial and spatiotemporal correlations to estimate trawl catches in unsampled areas based on sampled catches from neighbouring areas and years. In Chapter 1 I provide an overview of the redfish fishery and background on index standardization. In Chapter 2 I test different temporal and spatiotemporal structures for a model and use the best-performing model to predict catches in unsampled areas and therefore fill the gaps in survey coverage. I also quantify the uncertainties due to these predictions and generate new standardized survey abundance indices for the stock. There is also the possibility in the future of reductions in survey efforts in many regions in Subarea 2 + Division 3K, especially the near-shore and deep-water strata. Therefore, in Chapter 3, I test various survey configurations to assess the consequences of further reduction in sampling.

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