Synoptic postfishery structure of invertebrate bycatch associated to Zygochlamys patagonica fishing grounds at SW Atlantic shelf-break front (39°S, Argentina)

Abstract

Biological data were collected in a Patagonian scallop fishing ground, between 39° 00′ and 39° 50′ S and between 87 and 130 m depth. During 2007, we sampled the following stations where the trawling exerted could be precisely determined: 11 locations subjected to continuous fishing effort between 1996 and 2006 (continuous fishing effort, 878 commercial tows) and 12 locations subjected to fishing effort between 1996 and 2002 (interrupted fishing effort, 302 commercial tows). Univariate (species richness, Shannon's diversity index, and Pielou's equitability index) and multivariate analysis, analysis of variance, and Kruskal-Wallis tests were applied to analyze species composition and biomass. This study reflects the significant higher density of sessile taxa (Porifera and the ascidean Paramolgula gregaria) and two small ophiuroids (Ophiacantha vivipara and Ophiura lymani), all of them conspicuous during the exploratory cruises conducted in 1995, in the sites where fishing effort was interrupted 4 y before the sampling in 2007 than in those sites continuously exploited and discusses the results considering previous knowledge on the damage that the process on board scallopers imparts on invertebrates bycatch.