| dc.description | Since the beginning of the Patagonian scallop fishery Zygochlamys patagonica, in the Argentine Sea in 1996, an On-Board Observers Program (OBOP) was established at the National Institute of Fishery Research and Development (INIDEP). The general trends of the bycatch composition and biomass were analysed from information on catches and fishing effort (219 trips, 575 samples), collected in five scallop beds between 39º and 44º S during the period 1997-2002, provided by the OBOP. Large variations in average density of bycatch and the presence of eight taxonomic groups were determined during the study period. Echinodermata was the dominant taxon in most of the scallop beds. Echinoderms and gastropods showed an increase in biomass and sessile organisms were scarce in the SWSAO bed, subjected to high and continuous fishing effort. In the SWTB bed, with the lowest fishing effort, sessile organisms showed a decrease during the study period, while no variations occurred in the case of echinoderms and gastropods. The mentioned groups, mainly scavengers and predators, would be favoured by fishing activity that increased food availability (discards and damaged organisms). Contrarily, potential settlement substrates as sessile organisms, decreased in areas with intensive fishing activities. We stress out the validity of this source of data, which widens the spatio-temporal coverage of the yearly stock assessment cruises and is optimal for producing long-term databases. | |
