[MARMAM] Recent papers on estimating sustainable bycatch limits and animal welfare implications of bycatch mitigation in Conservation Biology and Marine Policy

Simon Allen simon.allen at bristol.ac.uk
Wed Aug 10 00:41:56 PDT 2022

G’day Marmamers,

The recent paper “A stochastic model for estimating sustainable limits to wildlife mortality in a changing world” (https://conbio.onlinelibrary.wiley.com/doi/10.1111/cobi.13897) introduced a new method for assessing if we are “taking too many” in, amongst other things, our seemingly insatiable hunger for marine wildlife. This paper has attained the #1 Attention Score of over 3,600 outputs from Conservation Biology tracked by Altmetric (https://wiley.altmetric.com/details/122229482#score), and we hope the method might prove broadly useful to scientists, managers, consultants and decision-makers going forward. Please reach out to the corresponding author if you’d like to discuss it further (Oliver Manlik: o.manlik at unsw.edu.au<mailto:o.manlik at unsw.edu.au>).

Sticking with the bycatch theme, I am also pleased to bring to your attention (on behalf of a different suite of co-authors) a recent publication in Marine Policy:

Dolman S, Breen C, Brakes P, Butterworth A, Allen SJ 2022. The individual welfare concerns for small cetaceans from two bycatch mitigation techniques. Marine Policy 143: 105126. https://doi.org/10.1016/j.marpol.2022.105126

Abstract: The prevalence of small cetacean (including dolphins, porpoises and small odontocete whales) bycatch in fisheries worldwide remains an ongoing conservation and welfare challenge. Various mitigation methods have been implemented in attempts to reduce bycatch. Two such methods involve gear modification: placement of Bycatch Reduction Devices (BRDs) within trawl nets<https://www.sciencedirect.com/topics/earth-and-planetary-sciences/trawl-net>, usually involving a physical barrier and an escape hatch; and, deployment of Acoustic Deterrent Devices (ADDs, ‘pingers’), typically placed on static nets and some trawl nets, to alert cetaceans to their presence and deter them from interacting with the gear. Despite their efficacy in reducing bycatch under certain circumstances, negative welfare impacts remain for individuals interacting with both BRDs and ADDs. Post-mortem analyses of small cetaceans caught in trawl gear, for example, illustrate the potential long-term effects of capture myopathies and cardiac damage sustained during the acute stress of entanglement<https://www.sciencedirect.com/topics/engineering/entanglement>, prior to and during escape through the BRD. Further, animals may become entangled in the bars, ropes or mesh of the BRD or escape hatch itself, and little is known of their post-release survival. ADD efficacy is typically fishery- and cetacean species-specific and, even where deemed a success at reducing bycatch, displacing animals from their optimal foraging habitat could negatively impact individual survival. Some species display equivocal responses to ADDs, while others may habituate to or be attracted to the sounds produced as they learn to associate it with food rewards, as they do in trawl fisheries, thereby reducing ADD efficacy and increasing the likelihood of entanglement. Here, we provide a synthesis of existing studies of these mitigation methods and discuss the associated welfare issues, where poor welfare negatively impacts an individual’s physical or mental state. We conclude that cetacean welfare considerations should become an integral part of decision-making in relation to bycatch globally.

Please contact the corresponding authors if you have any queries or would like a PDF of the manuscript (Sarah Dolman sarahdolman at eia-international.org<mailto:sarahdolman at eia-international.org> or Charlotte Breen charlotte.breen at icloud.com<mailto:charlotte.breen at icloud.com>).

All the best, Simon

Dr Simon J Allen
Senior Lecturer
School of Biological Sciences
University of Bristol

Mob: +44 (0) 77047 53101 [UK] / +61 (0) 416 083 653 [AU]
Email: Simon.Allen at bristol.ac.uk<mailto:Simon.Allen at bristol.ac.uk> / Simon.Allen at uwa.edu.au<mailto:Simon.Allen at uwa.edu.au>
Web: http://www.sharkbaydolphins.org
Twitter: @SimonJAllen1

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Recent papers: Estimating sustainable limits to human-caused wildlife mortality https://conbio.onlinelibrary.wiley.com/doi/abs/10.1111/cobi.13897
Cooperation-based concept formation in bottlenose dolphins https://www.nature.com/articles/s41467-021-22668-1
Non-vertical transmission of a dolphin foraging innovation https://www.cell.com/current-biology/fulltext/S0960-9822(20)30756-9
Declines in dolphin survival and reproduction following a heatwave https://www.cell.com/action/showPdf?pii=S0960-9822%2819%2930217-9

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