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

Abstract

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.

Long-term changes in the spiny dogfish (Squalus acanthias) trophic role in the southwestern Atlantic

“…Repeated trawling has profound effects on the trophic structure and function of benthic communities reducing their productivity (Jennings et al, 2001). In the study area, Carranza & Horta (2008) have found that 12 gastropod species may be potentially affected by trawling in the southwestern Atlantic, especially by hake fisheries (Carranza, 2006).…”

Coexistence patterns of benthic gastropods on the Uruguayan shelf

“…In our study, at least three datasets showed this pattern. Carranza and Horta (2008) showed a spatial segregation of gastropod assemblages along bathymetric and latitudinal gradients, thus making habitat partitioning a likely hypothesis toexplain the high C‐score for this dataset. However, in nearly all cases (with the exception of dataset 4), and despite differences in sampling gears, the area surveyed was large enough to encompass significant environmental variability, the same fact observed by Carranza et al (2008d) by means of a clustering analysis of stations based on biological data.…”

“…1); (B) Carranza et al 2008c; (C): Carranza and Scarabino unpubl. 2), (D): Carranza and Horta 2008; (E): Layerle and Scarabino 1984 and (F): Milstein et al 1976.…”

“…In our study, at least three datasets showed this pattern. Carranza and Horta (2008) showed a spatial segregation of gastropod assemblages along bathymetric and latitudinal gradients, thus making habitat partitioning a likely hypothesis to Table 1.…”

Impact of the clam Arca zebra artisanal fishery upon the population of the neogastropod Voluta musica in eastern Venezuela

“…Although bycatch is widely recognized as a threat to marine biodiversity and fisheries sustainability (Pauly et al, 2002), few studies have quantified bycatch of invertebrates and the effect on their populations in South America (Riestra et al, 2006;Escolar et al, 2009;Morsan, 2009) and specifically, gastropod bycatch is poorly registered (but see Carranza, 2006;Riestra et al, 2006;Carranza & Horta, 2008). The bycatch of benthic invertebrates may have negative impacts on some species, but some other (scavenger gastropods, crabs, and echinoderms) may increase population densities (Collie et al, 1997;Juan et al, 2007;Escolar et al, 2009).…”