Review of potential line-transect methodologies for estimating abundance of dolphin stocks in the eastern tropical Pacific
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A twelve-year hiatus in fishery-independent marine mammal surveys in the eastern tropical Pacific Ocean (ETP), combined with a mandate to monitor dolphin stock status under international agreements and the need for reliable stock status information to set dolphin bycatch limits in the tuna purse-seine fishery, has renewed debate about how best to assess and monitor ETP dolphin stock status. The high cost of replicating previous ship-based surveys has intensified this debate. In this review, transect methods for estimating animal abundance from dedicated research surveys are considered, with a focus on both contemporary and potential methods suitable for surveying large areas for dolphin species that can form large, multi-species aggregations. Covered in this review are potential improvements to the previous ship-based survey methodology, other ship-based methods, alternative approaches based on high-resolution imagery and passive acoustics, and combinations of ship-based and alternative approaches. It is concluded that for immediate management needs, ship-based surveys, with some suggested modifications to improve precision, are the only reliable option despite their high cost. However, it is recommended that a top research priority should be development of composite methods. Pilot studies on the use of high-resolution imagery and passive acoustics for development of indices of relative abundance to be used in composite methods should be part of any future ship-based survey efforts.
Lennert-Cody , C E , Buckland , S T , Gerrodette , T , Webb , A , Barlow , J , Fretwell , P T , Maunder , M N , Kitakado , T , Moore , J E , Scott , M D & Skaug , H J 2019 , ' Review of potential line-transect methodologies for estimating abundance of dolphin stocks in the eastern tropical Pacific ' , Journal of Cetacean Research and Management , vol. 19 , pp. 9-21 . < https://archive.iwc.int/?r=7931 >
Journal of Cetacean Research and Management
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