High mortality of adult female Magellanic penguins by gillnet fisheries in southern Brazil

Abstract

Bycatch in gillnet fisheries is one of the main threats to several penguin species. Magellanic penguins (Spheniscus magellanicus) are caught by gillnets during their wintering in southern Brazil. However, current information is based only on a small number of sets observed during a single fishing trip. This study assesses bycatch rates of bottom and drift gillnets operating in southern Brazil, and describes the sex and age classes of individuals captured. In 80 bottom gillnet sets, 33 penguins were captured (85% adults), 14 were sexed of which 13 were females. In 41 drift gillnet sets, four penguins were captured, three of which were juveniles. The mean bycatch rates, measured as number of penguins km−2 of net and number of penguins km−2 h−1, were significantly higher for the drift gillnets. Despite the lower bycatch rates, owing to the higher fishing effort in terms of number of boats, net length, net area, soak time and fishing season, the magnitude of penguin bycatch in the bottom gillnet fishery cannot be ignored. Despite based on small sample size, the predominance of adult and female Magellanic penguins as bycatch in gillnet fisheries in southern Brazil agrees with previous studies suggesting that females displace further north than males. In addition, such evidence contributes to the male‐biased sex ratio in breeding grounds, and the long‐term decline of major Patagonian colonies owing to higher female mortality during winter.

Postmortem findings in Magellanic penguins (Spheniscus magellanicus) caught in a drift gillnet

“…The age groups described in previous reports of penguin bycatch in Brazil are contradictory. Vanstreels et al [22] and the present study reported mostly juveniles, respectively, 100 and 95%, while Cardoso et al [9], Marques et al, 2018 [10], and Fogliarini et al, 2019 [11] identified mostly adults (respectively, 81, 77 and 53%).…”

“…Their potential impact in regards to bycatch may not be comparable with fishing nets used by commercial fisheries (e.g., longer and used offshore); however, gillnets are still a threat to penguins. Previous reports evidenced the gillnet bycatch of a large number of penguins in southern Brazil [8][9][10][11]; nonetheless, these studies did not perform complete postmortem examinations.…”

Sex-specific spatial use of the winter foraging areas by Magellanic penguins and assessment of potential conflicts with fisheries during winter dispersal

“…Fisheries by-catch mortality has been documented for Magellanic penguins all along its distributional range, especially in areas of high fishing effort during the autumn and winter periods off the coast of Argentina (e.g., [20][21][22]. Also, a female-biased mortality was found in carcasses of Magellanic penguins' overwintering grounds in southern Brazil among individuals died by starvation [23], and a female-biased mortality in by-catch of gillnet fisheries [24]. In northern Patagonia, a study reported that the non-breeding-season survival of females was lower than in males, thereby influencing population growth rate [25].…”

Long‐term changes in fishery resources of an estuary in southwestern Atlantic according to local ecological knowledge

“…The current situation of overfishing for several artisanal fishing resources in the PLE, as demonstrated by this study, and for industrial resources in the coastal region as demonstrated by Haimovici and Cardoso (2016a), requires the attention of fishery managers. However, there is a clear lack of proper management measures or enforcement in southern Brazil, as several threatened marine megafauna species are killed annually in high numbers and most of the fish resources are overexploited (Fogliarini, Bugoni, Haimovici, Secchi, & Cardoso, 2019;Haimovici & Cardoso, 2016b;Prado, Mattos, Silva, & Secchi, 2016, this study). From a governance context of lack of enforcement or ineffective management or conservation strategies, Dowling et al (2016)…”