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Regional oceanography drives humpback whale entanglement in Queensland shark-control nets
Conference presentation

Regional oceanography drives humpback whale entanglement in Queensland shark-control nets

Jessica Bolin, David S Schoeman, Carmen Piza Roca and Kylie L Scales
Australian Marine Science Association Annual Conference (Fremantle, Australia, 07-Jul-2019–11-Jul-2019)
Australian Marine Sciences Association
2019
url
http://amsa19.amsa.asn.auView
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Abstract

Ecology biological oceanography remote sensing marine ecology
Shark-control nets pose an entanglement risk to East Australian humpback whales during their annual migrations. Understanding entanglement risk requires knowledge of the mechanisms involved in whale navigation, and the influence of contemporaneous environmental cues, including the East Australian Current (EAC). This study provides a quantitative spatio-temporal analysis of associations between the position and strength of the EAC and the likelihood of entanglements in shark-control nets. We use remotely-sensed sea-surface temperature, and outputs from a data-assimilating ocean model, to develop algorithms for detecting the EAC using Principal Components Analysis, which are used to model the likelihood of humpback entanglement in Southeast Queensland. We find elevated risk of entanglement when the EAC inner edge was closer to shore, and when the physical gradient marking the inner edge of the EAC was poorly defined. Our results suggest humpbacks use the inner edge of the EAC as a navigational aid. Our findings can be integrated into management to improve predictive capacity of future entanglements, thus aiding and preventing whale injuries and fatalities. Our approach is applicable to other commonly entangled species, which could underpin a more holistic, data-driven approach to bycatch mitigation in the Queensland Shark Control Program, and other programs involving static fishing gear.

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