Review of potential line-transect methodologies for estimating abundance of dolphin stocks in the eastern tropical Pacific

Cleridy E. Lennert-Cody*, Stephen T. Buckland, Tim Gerrodette, Andrew Webb, Jay Barlow, Peter T. Fretwell, Mark N. Maunder, Toshihide Kitakado, Jeffrey E. Moore, Michael D. Scott, Hans J. Skaug

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

2 Citations (Scopus)

Abstract

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.
Original languageEnglish
Pages (from-to)9-21
Number of pages13
JournalJournal of Cetacean Research and Management
Volume19
Publication statusPublished - 25 Jan 2019

Keywords

  • Abundance estimate
  • Index of abundance
  • Trends
  • Survey-vessel
  • Survey-aerial
  • Survey-acoustic
  • Survey-combined

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