Seabird interactions and by‐catch in the anchovy pelagic trawl fishery operating in northern Argentina

Abstract

Commercial fishing has been identified as one of the main threats affecting the survival of most seabird species. Although seabird mortality in Argentine longline and demersal trawl fisheries has already been characterized and quantified, the interactions with pelagic trawl fisheries targeting anchovy (Engraulis anchoita Hubbs & Marini, 1935) remains unknown. The goal of this study was to characterize seabird assemblages attending pelagic trawl vessels and to analyse their interactions (i.e. contact of the birds with the vessel and/or fishing gear and by‐catch). Data were obtained by on‐board observers during three consecutive fishery runs, 2011–2013. From a total of 333 observations, seabird abundance averaged 157.3 ± 229.7 birds per haul (totalling 23 species). Procellariiform followed by Charadriiform birds were the more frequent and abundant groups. The black‐browed albatross (Thalassarche melanophris (Temminck, 1828)), shearwaters (Ardenna spp. and Puffinus spp.), white‐chinned petrel (Procellaria aequinoctialis Linnaeus, 1758), and the kelp gull (Larus dominicanus Lichtenstein, 1823) were the most frequent and abundant attending species. The seabird abundance increased when the swell and the number of neighbouring vessels decreased. Seabird interactions with the vessel and/or fishing gear occurred in approximately 70% of the observations, with most of these representing interactions with the net (92%). The estimated contact rate was 16.7 birds h−1 per haul. A total of 121 birds were by‐caught and the average mortality rate was 0.55 birds h−1 per haul. Shearwaters and Magellanic penguins (Spheniscus magellanicus (Forster, 1781)) were the main by‐caught species (101 and 12 individuals, respectively). Lower levels of mortality were recorded in black‐browed albatrosses and white‐chinned petrels. The interactions increased in the presence of fishing discards and during haulback operations. This study is relevant to the implementation of the Argentine National Plan of Action – Seabirds, as well as for the continuing certification process in the anchovy fishery.

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

“…This supports the assumption that the destination areas recorded are representative of the areas exploited by the larger breeder's population. On the other hand, despite a possible overestimation of overlap with fisheries by using a large pixel, regions of high overlap corresponded fairly well with regions of documented interaction with Magellanic penguins [22,27,[57][58][59]. However, we acknowledge that inference drawn from these low sample sizes and spatial resolution deserves caution.…”

“…Seabirds-fisheries interactions are a result of the overlap between the foraging areas used by seabirds and the areas used by the fisheries. 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].…”

Incidental capture of seabirds in Argentinean side-haul trawlers

“…This fleet has a dynamic fishing strategy, primarily targeting Argentine Hake with an average annual catch of 67,323 mt, but also skates (Rajidae; 6,579 mt) and Kingklip Genypterus blacodes (4,012 mt). Depending on the season, vessels may change fishing gear and/or fishing zone to target Argentine Anchovy (6,954 mt; see Paz et al 2018) and Atlantic Chub Mackerel Scomber colias (6,248 mt). Some vessels also target Argentine Red Shrimp.…”

“…Interactions between seabirds and trawl cables in the Patagonian Shelf are well known in several fisheries targeting predominantly finfish species. This includes factory trawlers that target Southern Blue Whiting Micromesistius australis , Hoki Macruronus magellanicus and Patagonian Toothfish Dissostichus eleginoides (Sullivan et al 2006b, Tamini et al 2019), the Argentine Anchovy Engraulis anchoita fishery (Paz et al 2018), the offshore Argentine Hake Merluccius hubbsi trawl fishery in San Jorge Gulf (González-Zevallos and Yorio 2006, González-Zevallos et al 2007) and Northern Patagonia (Seco Pon 2014), and industrial vessels along the Patagonian Shelf (Favero et al 2011, González-Zevallos et al 2011, Tamini et al 2015). The most affected seabirds are albatrosses, petrels, and shearwaters.…”

“…Seabird interactions with the net have been observed in the same area by fishing fleets targeting a variety of species. This includes the Argentine Red Shrimp Pleoticus muelleri fishery in San Jorge Gulf (Gandini et al 1999), the Silverside Odonthestes incisa fishery (Tamini et al 2002), the Argentine Anchovy fishery (Paz et al 2018), the Argentine Red Shrimp and Argentine Hake coastal fisheries in Northern and Central Patagonia (Yorio and Caille 1999, Marinao and Yorio 2011, Marinao et al 2014), the high seas Argentine Hake trawl fishery in San Jorge Gulf (González-Zevallos and Yorio 2006, González-Zevallos et al 2007) and by industrial vessels along the Patagonian Shelf (Favero et al 2011, González-Zevallos et al 2011, Tamini et al 2015). Species observed interacting with these fisheries include penguins, cormorants, albatrosses, petrels, and shearwaters.…”