Beyond Post-release Mortality: Inferences on Recovery Periods and Natural Mortality From Electronic Tagging Data for Discarded Lamnid Sharks

Type Article
Date 2021-04
Language English
Author(s) Bowlby Heather D.1, Benoît Hugues P.2, Joyce Warren1, Sulikowski James3, Coelho Rui4, 5, Domingo Andrés6, Cortés Enric7, Hazin Fabio8, Macias David9, Biais Gerard10, Santos Catarina4, 5, Anderson Brooke3
Affiliation(s) 1 : Bedford Institute of Oceanography, Fisheries and Oceans Canada, Dartmouth, NS, Canada
2 : Institut Maurice-Lamontagne, Fisheries and Oceans Canada, Mont-Joli, QC, Canada
3 : School of Mathematical and Natural Sciences, Arizona State University, Glendale, AZ, United States
4 : Portuguese Institute for the Ocean and Atmosphere (IPMA, I.P.), Olhão, Portugal
5 : Centre of Marine Sciences of the Algarve (CCMAR), University of Algarve, Faro, Portugal
6 : Laboratorio de Recursos Pelágicos, Dirección Nacional de Recursos Acuáticos, Montevideo, Uruguay
7 : Panama City Laboratory, NOAA Fisheries, Southeast Fisheries Science Center, Panama, FL, United States
8 : Department of Fishing and Aquaculture, Universidade Federal Rural de Pernambuco, Recife, Brazil
9 : Oceanographic Center of Malaga, Spanish Institute of Oceanography, Málaga, Spain
10 : Ifremer, Laboratoire LIENSs, Université de La Rochelle, Nantes, France
Source Frontiers in Marine Science (2296-7745) (Frontiers Media SA), 2021-04 , Vol. 8 , P. 619190 (14p.)
DOI 10.3389/fmars.2021.619190
Keyword(s) Natural mortality, recovery period, lamnid sharks, Atlantic, survival, mitigation, bycatch
Abstract

Accurately characterizing the biology of a pelagic shark species is critical when assessing its status and resilience to fishing pressure. Natural mortality (M) is well known to be a key parameter determining productivity and resilience, but also one for which estimates are most uncertain. While M can be inferred from life history, validated direct estimates are extremely rare for sharks. Porbeagle (Lamna nasus) and shortfin mako (Isurus oxyrinchus) are presently overfished in the North Atlantic, but there are no directed fisheries and successful live release of bycatch is believed to have increased. Understanding M, post-release mortality (PRM), and variables that affect mortality are necessary for management and effective bycatch mitigation. From 177 deployments of archival satellite tags, we inferred mortality events, characterized physiological recovery periods following release, and applied survival mixture models to assess M and PRM. We also evaluated covariate effects on the duration of any recovery period and PRM to inform mitigation. Although large sample sizes involving extended monitoring periods (>90 days) would be optimal to directly estimate M from survival data, it was possible to constrain estimates and infer probable values for both species. Furthermore, the consistency of M estimates with values derived from longevity information suggests that age determination is relatively accurate for these species. Regarding bycatch mitigation, our analyses suggest that juvenile porbeagle are more susceptible to harm during capture and handling, that keeping lamnid sharks in the water during release is optimal, and that circle hooks are associated with longer recovery periods for shortfin mako.

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Bowlby Heather D., Benoît Hugues P., Joyce Warren, Sulikowski James, Coelho Rui, Domingo Andrés, Cortés Enric, Hazin Fabio, Macias David, Biais Gerard, Santos Catarina, Anderson Brooke (2021). Beyond Post-release Mortality: Inferences on Recovery Periods and Natural Mortality From Electronic Tagging Data for Discarded Lamnid Sharks. Frontiers in Marine Science, 8, 619190 (14p.). Publisher's official version : https://doi.org/10.3389/fmars.2021.619190 , Open Access version : https://archimer.ifremer.fr/doc/00688/80020/