Megabenthic gastropods in the outer Uruguayan continental shelf: composition, distribution and some effects of trawling

this study aims to advance knowledge on the effects of bottom trawling in the shelled megabenthic gastropods from uruguayan continental shelf. composition of by-catch, species distribution, direct shell damage and mortality, and frequency of repaired shell damage were analysed from data collected on board of the research vessel "aldebaran". a total of 12 megabenthic gastropod species was registered from 35 stations surveyed, either as live specimens or empty shells. from these, the shelled gastropods adelomelon beckii, adelomelon ancilla, odontocymbiola magellanica, fusitriton magellanicus and zidona dufresnei dominated numerically the by-catch. we observed a spatial segregation of the gastropod assemblages along a bathymetric and latitudinal gradient, with o. magellanica, f. magellanicus and a. ancilla occurring at the southern portion of the study area, whereas a. beckii and z. dufresnei were restricted to the northern and shallower areas respectively. direct mortality was barely observed, but shells of a. ancilla, o. magellanica and z. dufresnei were frequently damaged during the fishing operation and capture handling. accordingly, we found a high positive correlation between the observed frequency of recent shell damage and the presence of scars, suggestive but not conclusive evidence on the relationship between incidence of repaired shell damage and trawling disturbance