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Assessing the potential for resource competition between the Kerguelen Plateau fisheries and southern elephant seals

Citation

Hindell, MA and McMahon, CR and Guinet, C and Harcourt, R and Jonsen, ID and Raymond, B and Maschette, D, Assessing the potential for resource competition between the Kerguelen Plateau fisheries and southern elephant seals, Frontiers in Marine Science, 9 Article 1006120. ISSN 2296-7745 (2022) [Refereed Article]


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DOI: doi:10.3389/fmars.2022.1006120

Abstract

Indirect ecological interactions such as competition for resources between fisheries and marine predators have often been proposed but can be difficult to demonstrate empirically. The Kerguelen Plateau in the Southern Indian Ocean supports fisheries for both Patagonian toothfish and mackerel icefish and is also an important foraging ground for several avian and mammalian predators, including the southern elephant seal. We quantified the spatio-temporal use of the plateau by southern elephant seals and found that males and females spent 30% of their time on the plateau within the commonly used fishing grounds, indicating the possibility of competition for resources there. We then contrasted the seals’ use of two habitat types, the benthos (where interactions with the long-line fisheries are most likely) and the epi-pelagic zone. The likelihood of feeding on the benthos declined as ocean depth increased and was also less likely at night. Males were also more likely to feed on the benthos than females. The sub-adult male seals consumed an estimated 6,814 – 14,848 tons of high energy content prey (including toothfish) and females 7,085 – 18,037 tons from the plateau during the post-molt winter months. For males this represented 79.6 - 173.4% of the mean annual catch by the Kerguelen fishery compared to 82.8 - 210.7% for adult females. When considering the seals consumption of fish from the benthos within the fishing grounds these estimates decreased to 3.6 - 15.1% of the fishery’s total annual catch for females and 7.8 - 19.1% for males. While this further indicates the possibility of indirect ecological interactions (with the fishery taking more fish than the seals), the lack of detailed diet information for the seals precludes us from establishing the degree or nature of the possible interactions because the importance of toothfish and icefish in the diet of the seals is unknown. However, the unique life history and highly polygynous nature of this species, and the lack of evidence of a measurable effect on either the seal’s population growth rates or the catch per unit of the fishery, suggest that any indirect ecological interactions are not of sufficient magnitude to affect either the seal population or the fishery.

Item Details

Item Type:Refereed Article
Keywords:seals, fisheries, Kerguelen Plateau, southern elephant seal, fisheries interactions, Patagonian toothfish, mackerel icefish
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Fisheries sciences
Research Field:Fisheries management
Objective Division:Animal Production and Animal Primary Products
Objective Group:Fisheries - wild caught
Objective Field:Fisheries - wild caught not elsewhere classified
UTAS Author:Hindell, MA (Professor Mark Hindell)
UTAS Author:McMahon, CR (Dr Clive McMahon)
UTAS Author:Raymond, B (Dr Ben Raymond)
UTAS Author:Maschette, D (Mr Dale Maschette)
ID Code:155019
Year Published:2022
Deposited By:Sustainable Marine Research Collaboration
Deposited On:2023-01-23
Last Modified:2023-01-23
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