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

We assessed for the first time marine bird and mammal attendance in the Chub mackerel Scomber japonicus semi-industrial coastal purse seine fishery in northern Argentina. Information was gathered during a fishery run from late spring 2007 to early summer 2008. Sixteen marine top predator species attended vessels, and the most abundant seabirds (percent of overall individuals and percent of occurrence) were the Kelp Gull Larus dominicanus (25% and 40% respectively), and White-chinned Petrel Procellaria aequinoctialis (24% and 47% respectively). Other attending bird species were the Black-browed Albatross Thalassarche melanophrys (18.5% and 12% respectively) and South American Tern Sterna hirundinacea (30% and 22% respectively). The most abundant marine mammal's species was the South American Sea Lion Otaria flavescens (2% and 8% respectively). Analysis of environmental and operational variability affecting the abundance of the four main seabird species indicated a clear spatial variability in the numbers of seabirds attending coastal purse seiners. Other factors included fishing operation, time of day, seasonality, and wind intensity and wind direction. Neither seabird nor marine mammal species were observed to be incidentally taken during 82 fishing operations. The results of this study showed that the semi-industrial purse seine fishery operating in coastal waters in northern Argentina may have a relatively minor impact on some marine top predator populations mainly because (1) the fishing grounds are close to shore, and at relatively shallow depths, and (2) for economic reasons, the fishing fleet operates at considerable distance from dense schooling areas. Still, it has to be stressed that data were obtained during operations in which the levels of discards (<2%) were by far lower than the average of 30% reported in the literature. Given this background, further studies including long-term monitoring are needed for an adequate modeling of the interactions and the identification of core areas for seabirds interacting with purse seiners in the waters of northern Argentina. (C) 2012 Elsevier Ltd. All rights reserved.