Low Resighting Rate of Entangled Humpback Whales Within the California, Oregon, and Washington Region Based on Photo-Identification and Long-Term Life History Data

Jennifer Tackaberry; Elana Dobson; Kiirsten Flynn; Ted Cheeseman; John Calambokidis

doi:10.3389/fmars.2021.779448

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Low Resighting Rate of Entangled Humpback Whales Within the California, Oregon, and Washington Region Based on Photo-Identification and Long-Term Life History Data

Jennifer Tackaberry, Elana Dobson, Kiirsten Flynn, Ted Cheeseman and John Calambokidis

Frontiers in Marine Science, Vol.8, pp.1-13

28/01/2022

DOI: https://doi.org/10.3389/fmars.2021.779448

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Abstract

Environmental Sciences

Environmental Sciences & Ecology

Life Sciences & Biomedicine

Marine & Freshwater Biology

entanglement

humpback whale

life history

Megaptera novaeangliae

photo-identification

resighting rate

survival

West Coast USA

Bycatch, commonly referred to as entanglement, is a leading source of human-caused mortality of baleen whales. A better understanding of the individuals that survive (or perish from) their entanglement can help reduce the risk of bycatch by informing gear modifications and fisheries management. However, determining survival rates is restricted by the ability to track individuals once they become entangled. Historically, the effort to identify and resight individuals from known entanglement cases was low along the West Coast. The recent increase of entanglements and photo-identification efforts in the California, Oregon, and Washington region provides an opportunity to assess entangled humpback whales’ resighting rates to better understand the effect of entanglements from the individual to the population level. We used photo-ID images of entangled humpback whales between 1982 and 2017 to examine pre- and post-entanglement sighting histories from longitudinal catalogs and life history data (Cascadia Research and Happywhale). We compared the entangled whales (n = 37) against control whales (n = 2,296), selected based on the date and location of the entanglement reports, to evaluate the deviation from the expected mortality rates (or lack of resighting) caused by entanglements and to help inform/support/test National Oceanic and Atmospheric Association’s Serious Injury and Mortality (SI/M) index. Our results suggest that entangled whales were resighted less often than the control groups. Entangled whales with short pre-entanglement sighting histories and without post-entanglement resights did not match other feeding ground populations. Therefore, the higher proportion of entanglements with shorter sighting histories is likely due to their being alive for fewer years, indicating a higher risk of entanglement for younger whales. This indicates that entangled humpback whales may not be as large or strong as mature individuals, and future gear modifications should reflect that possibility. Additionally, the severity of the initial SI/M score aligned well with our resighting rates, though this worsened with the final score assigned. Continued effort to gather and improve data collection about entanglements will help enhance the SI/M determinations. Our findings show the value of photo-identification of entangled whales and how it dramatically increases our understanding of entanglements.

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Title: Low Resighting Rate of Entangled Humpback Whales Within the California, Oregon, and Washington Region Based on Photo-Identification and Long-Term Life History Data
Creators: Jennifer Tackaberry - Cascadia Research Collective
Elana Dobson - Cascadia Research Collective
Kiirsten Flynn - Cascadia Research Collective
Ted Cheeseman - Southern Cross University
John Calambokidis - Cascadia Research Collective
Publication Details: Frontiers in Marine Science, Vol.8, pp.1-13
Publisher: Frontiers Media Sa
Number of pages: 13
Grant note: NOAA as part of several grants/contracts, including a Section 6 grant through the Washington Department of Fish and Wildlife
Identifiers: 991013054709202368
Copyright: Copyright © 2022 Tackaberry, Dobson, Flynn, Cheeseman and Calambokidis. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Academic Unit: Faculty of Science and Engineering
Language: English
Resource Type: Journal article

Low Resighting Rate of Entangled Humpback Whales Within the California, Oregon, and Washington Region Based on Photo-Identification and Long-Term Life History Data

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