Seabird and marine-mammal attendance and by-catch in semi-industrial trawl fisheries in near-shore waters of northern Argentina

Abstract

Seabird and marine-mammal attendance and by-catch in mid-water and bottom otter semi-industrial coastal pair-trawl fisheries were assessed for the first time in northern Argentina. Observers were placed onboard trawlers between autumn 2007 and autumn 2008. Fifteen marine top-predator species were associated with the vessels. The most abundant and frequent seabirds (trawl fisheries combined) were the kelp gull, Larus dominicanus (~70% of total birds and >96% occurrence), and the Olrog’s gull, L. atlanticus (~12% and >50%, respectively). Other seabird taxa such as Procellariiforms and Sphenisciforms, among others, were represented in very low numbers. The only mammal species recorded was the South American sea lion, Otaria flavescens (1% and 2%, respectively). Analysis of environmental and operational variability affecting the abundance of gulls indicated a significant increase in abundance with fishing depth, time of day, seasonality, wind intensity and wind direction. Incidental mortality of top predators was low and comprised only Magellanic penguins, Spheniscus magellanicus, in the mid-water gear. The results of the present study showed that the semi-industrial trawl fisheries operating in coastal waters in northern Argentina may a have a relatively minor impact on marine top-predator populations, at least in terms of incidental capture.

Captura incidental de um leão-marinho-sul-americano na pesca de arrasto de parelha no sul do Brasil

“…Although the reasons for this population decline are still unknown, the interactions with fishing activities have been identified as a major cause of threat to the conservation of South American sea lions (IUCN, 2013;Crespo et al, 2012). Records of catches of South American sea lions by fishing activities are reported for gillnet fisheries in Peru (Majluf et al, 2002), Chile (Sepúlveda et al, 2007) and Uruguay (Franco-Trecu et al, 2009), for purse seine fisheries in Chile (Hückstädt and An-tezana, 2003) and Argentina (Seco Pon et al, 2013); and for trawling fisheries in Argentina (Crespo et al, 1997;Dans et al, 2003) and Chile (Reyes et al, 2013). Thus, this paper presents the first record of incidental catch of the South American sea lions in Brazilian waters and by a pair trawl fishery.…”

Sea lion and fur seal interactions with fisheries and aquaculture in South American waters: threats and management perspectives

“…Larger SASL numbers were recorded off Peru, where up to 3000 individuals (mean ± standard deviation: 62 ± 114) were counted interacting with purse seine gear between 2015 and 2019 (Rivadeneyra‐Villafuerte & Román‐Amancio 2022). Off northern Argentina, the maximum number of SASLs reported was two in the semi‐industrial mid‐water trawl fishery, and in the bottom pair‐trawl fishery the maximum number reported was three, with a mean of 0.7 (± 1) SASLs (Seco Pon et al 2013). Lower numbers of SASLs in trawl fisheries may be explained because, contrary to purse seines, fish caught in trawl nets are confined in a small space, which is a dangerous place for SASLs to forage (Northridge 2018).…”

Contribution of recreational fisheries to the diet of the opportunistic Kelp Gull

“…A large number of studies have described the consumption by Kelp Gulls of fishery discards provided by offshore commercial trawl fishing operations in Argentina (e.g. Yorio & Caille 1999;Bertellotti & Yorio 2000;Gonz alez-Zevallos & Yorio 2006;Marinao & Yorio 2011;Seco Pon et al 2013) and in other coastal sectors of South America and Southern Africa (Abrams 1983;Branco 2001;Villablanca et al 2007;Soares Traversi & Vooren 2010;Carniel & Krul 2012). As in the Bah ıa San Blas protected area, Kelp Gulls have been recorded taking advantage of waste derived from the on-land processing of the catch from artisanal fisheries in Brazil (Carniel & Krul 2011) and at fish processing plants associated to commercial trawl fisheries in Argentine Patagonia (Yorio & Caille 2004).…”