Whale depredation in the South Georgia Patagonian toothfish (Dissostichus eleginoides) fishery in the South Atlantic: a comparison of estimation methods

Earl, Timothy, MacLeod, Eleanor, Söffker, Marta, Gasco, Nicolas, Massiot-Granier, Félix, Tixier, Paul and Darby, Christopher (2021) Whale depredation in the South Georgia Patagonian toothfish (Dissostichus eleginoides) fishery in the South Atlantic: a comparison of estimation methods. ICES Journal of Marine Science, 78 (10). pp. 3817-3833. ISSN 1054-3139

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Abstract

Removal of fish from gear by marine predators, known as depredation, is a fishery dependent mortality that needs to be included in stock assessments for affected stocks to avoid misestimation of the assessed resource. Toothed whales engage regularly in depredation from longlines, and while in some regions they leave clear marks of depredation activity, in the longline fisheries in the Southern Ocean they often leave no trace of removal, making it necessary to estimate depredation through modelling approaches. Several modelling approaches have been developed over the past decade in affected Southern Ocean fisheries, and in this paper, we examine five applications of common CPUE model structures to the same dataset from the longline fishery around South Georgia. We then compare the estimates of depredation with those based on observed bycatch ratios. The different model structures estimated very similar annual depredation removals, with all approaches averaging around 5% of the catch removed throughout the entire fishery. While depredation varies spatially, the different modelling approaches consistently highlighted areas where the impact of depredation was highest.

Item Type: Article
Additional Information: Data availability statement: Data access is governed by the Rules for the Access and Use of CCAMLR Data https://www.ccamlr.org/en/document/publications/rules-access-and-use-ccamlr-data
Uncontrolled Keywords: depredation,longline,marine mammal,modelling,odontocete,south atlantic,south georgia,killer whales,orcinus-orca,sperm-whales,longline fisheries,physeter-macrocephalus,relative abundance,fishing practices,marine mammals,crozet,sablefish,sdg 14 - life below water ,/dk/atira/pure/sustainabledevelopmentgoals/life_below_water
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: LivePure Connector
Date Deposited: 11 Feb 2022 16:30
Last Modified: 14 Feb 2022 11:31
URI: https://ueaeprints.uea.ac.uk/id/eprint/83438
DOI: 10.1093/icesjms/fsab212

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