Interactions between Marine Mammals and high seas fisheries in Patagonia under an integrated approach

DANS SILVANA LAURA; KOEN-ALONSO MARIANO; CRESPO ENRIQUE ALBERTO; PEDRAZA SUSANA NOEMI; GARCÍA NÉSTOR ANÍBAL

Marine Mammals: Fisheries; Tourism and Management Issues

CSIRO Publishing Collingwood Vic.

Lugar: Collingwood, Victoria; Año: 2003; p. 88 - 103

DISCUSSION AND PERSPECTIVESThe study of interactions between marine mammals and trawlingfisheries in Patagonia during the 1990s was probably one ofthe most integrative studies carried out with these fisheries.Trawls had been less surveyed than other fishing gear, like purseseinesor gillnets, and their effects on the marine environmenthad probably been underestimated (Perez and Loughlin 1991;Fertl and Leatherwood 1997; Crespo et al. 2000). The strongcapacity for biomass extraction by trawlers needed the evaluationof both operational and ecological impacts. This was thescope of the research carried out in Patagonia, which turnedfrom a pristine regional sea in the early 1980s, to a heavilyimpacted sea in the late 1990s.Dynamics of the fishery includes rapid changesThe trawl fishery in Argentine Patagonia has changed considerablyduring the last two decades. During the 1980s, this changewas an increase in fishing effort and the targeting of differentresources; in the late 1990s, it was as a consequence of thedecline and replacement of target species. In the middle of thisprocess, the total bycatch of top predators climbed up and downaccording to the fishing effort, always under the assumption thatmortality rates remained constant. The most important changesrelated to marine mammal mortality are those experienced bymid-water trawling for shrimp during the 1980s, and in the lastfew years, mid-water trawling for Argentine anchovies. Thesefacts resulted in temporal increases of mortality of dusky andcommon dolphins. Mid-water trawling for anchovy represents apotentially important source of marine mammal mortality, andthis fishery may develop as a consequence to the collapse of thehake fishery. With relatively low effort, the mortality levelscaused by this fishing type could be very high (Crespo et al.2000).