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Interactions between top predators and the coastal net fishery based in Mar del Plata, Buenos Aires Province, Argentina

Nets used in fishing operations worldwide are known to kill a variety of non-target organisms, including non-commercial fishes, seabirds, marine mammals and sea turtles worldwide. Argentine coastal waters are intensively used as a foraging area by a large number of marine top predators and also attract a large and diverse fishing fleet, resulting in documented seabird bycatch. Although there is information on the impact on birds and marine mammals of commercial net fisheries developed in Patagonia, the interactions in other regions are less documented, despite the fact that 81% of the national fleet fishing for coastal fish is concentrated in Buenos Aires Province. The aim of this project was to study the interactions between top predators and the coastal net fishery based in Mar del Plata (Buenos Aires Province), specifically to assess the incidental mortality of seabirds and other top predators associated with this fleet and the operational and environmental variables involved in that process.

During the 2007-08 fishing season, observers accompanied fishing vessels on 66 trips, collecting information on fishing operations, target fish catch, the number and identity (species, sex, age when known) of seabirds and marine mammals following the vessel, and contacts between seabirds/marine mammals and fishing gear. Twenty seabird and three marine mammal species were identified following net fishing vessels in the region, eleven more bird species than had been reported for the Patagonian fisheries. Seabirds and marine mammals were observed contacting fishing gear in 48% of sets; however, almost all interactions were light contacts resulting in no harm while seabirds and marine mammals were feeding on the catch. The white-chinned petrel and the southern sea lion were the seabird and marine mammal species observed interacting most frequently with fishing nets. The Magellanic penguin was the only species observed to be incidentally caught during the study (an estimated 40 individuals taken), and has also been reported caught in other fisheries and regions along the Argentina coast. These data are important for contributing to estimates of the potential cumulative impact on the Magellanic penguin population. The endangered Franciscana dolphin was observed following the fishing vessel, though no interactions were observed.

This study indicated that there do not appear to be significant seabird and marine mammal incidental mortality concerns given the current operational and management conditions of the net fishery off the coast of Buenos Aires province. Because the work was conducted in close collaboration and with the voluntary support of fishermen, the research team developed an important trusted relationship with the cooperative. In particular, if conditions change (e.g., discard policies, decline in other food sources), this relationship will be invaluable for continued investigations into the interactions – positive or negative – between marine top predators and Buenos Aires net fisheries.

See the publication Seabird and marine mammal attendance in the Chub mackerel Scomber japonicus semi-industrial Argentinian purse seine fishery.