Dear MARMAMers,
My co-author Andreas Winter and I are happy
to share our open-access paper published in Frontiers in Marine
Science: “Disentangling pinniped incidental mortality in a bottom-trawl
fishery with seal exclusion devices”.
*Keywords:* bottom-trawl, bycatch, drowning, incidental mortality,
pinniped, propeller strike, seal exclusion device.
*Abstract: *Seal exclusion devices (SED) fitted in trawls are recognized as
the best technical measure to mitigate pinniped bycatch, but do not
completely eliminate incidental mortality. In areas with high pinniped
abundance and concentrated fishing effort, identifying the cause of death
of pinniped carcasses in different stages of decomposition is challenging,
as the individuals could have died from a variety of causes. In the
Falkland Islands, best practice to mitigate and monitor incidental
mortality of South American fur seal (*Arctocephalus australis*) and South
American sea lion (*Otaria flavescens*) in the bottom-trawl Patagonian
squid (*Doryteuthis gahi*) fishery was introduced in 2017. From 2018
through 2023, best practice in the fishery included 100% dedicated observer
coverage and the use of SEDs. We analyzed 29,812 trawls (5,748 without a
SED and 24,054 with a SED) for pinniped bycatch (live SED escapes, live
deck releases, and mortalities) and corresponding catch and fishing effort,
post-mortem gross examinations, and multimedia data in the Patagonian squid
fishery. Mortalities in trawls without a SED included 45 drownings (fresh
carcasses) and two unknown (carcasses in different stages of
decomposition). Mortalities in trawls fitted with a SED included 53
drownings, 28 propeller strikes, and 26 unknown. Our results indicate that
SEDs are efficient at reducing incidental mortality, although low levels of
drownings continue during trawl hauling. These mortalities comprise mostly
males and are related to several operational variables and captain
performance, which was found to be heterogeneous in facilitating SED
escapes. In addition, we link for the first time propeller strike mortality
of South American otariids to a particular fishery, evidencing the
existence of this type of cryptic mortality in offshore trawl fisheries in
the Southwestern Atlantic. Since using SEDs, pinniped mortality levels in
the Patagonian squid fishery have been negligible at their population
levels. Results of this study can be used to work with captains to enhance
best practice and contribute to the sustainable management of the fishery.
*Link to the paper: *
https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2025.1588956/full
Kind regards,
Vero
--
Verónica Iriarte, MSc.
Bycatch Mitigation Officer (Seabirds & Marine Mammals)
Falkland Islands Fisheries Department FIQQ 1ZZ
Stanley
Falkland Islands
https://uy.linkedin.com/in/veronicairiarte
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