Seventeen years assessing biodiversity at Zygochlamys patagonica fishing grounds in the shelf break system, Argentina

LAURA SCHEJTER; ESCOLAR MARIANA; MARECOS A.; BREMEC CLAUDIA

Florianopolis

Workshop; 19th. International Pectinid Workshop; 2013

The Patagonian scallop Zygochlamys patagonica (King, 1832) is the key species of a fishery developed in the shelf break front of the SW Atlantic Ocean since 1996. The identification of invertebrate by-catch and the continuous monitoring of the benthic community associated with the Patagonian scallop were main goals of a complete management strategy. The exploration cruises developed one year before the beginning of the fishery (in 1995) established solid baseline information that allowed the characterization of the benthic community in the main Patagonian scallop fishing grounds, that totalize 72 invertebrate taxa in the shelf break system (Bremec & Lasta, 2002; Bremec et al., 1998). This baseline information (and posterior studies that continue until present) largely complemented general faunistic records from “Walther Herwig” exploration cruises developed between 1966 and 1978, results compiled in Walossek (1991). In 1995, the main benthic general assemblage at the Patagonian scallop fishing grounds was composed by the sponge Tedania sp., the anemone Actinostola crassicornis, the echinoderms Ophiactis asperula Ophiacantha vivipara, Ophiura lymani, Sterechinus agassizii, Cosmasterias lurida, Ctenodiscus australis, Psolus patagonicus and Pseudocnus dubiosus (Bremec & Lasta, 2002). This general assemblage persisted over time, with some slightly variations depending on the area (Bremec & Schejter, 2005; Bremec et al., 2009). Posterior studies updated and corrected taxonomical information based on collaborations with other research groups and also on new expertise acquired by members of the INIDEP Benthos Laboratory Team. In general, echinoderms represent one of the most important invertebrate groups in this community, reaching 86% of the by-catch biomass (Escolar et al., 2007; Escolar et al. 2009) with 23 species, some of them recorded as new distributional records (Escolar & Bremec, 2011). Sponge fauna reached more than 30 species, including not only new distributional records, but also descriptions of new sponge species (Bertolino et al., 2007; Schejter et al., 2011b; Schejter et al., 2006). Moreover, one new gastropod species was also described (Zelaya et al., 2011). Comparisons of invertebrate taxa richness among areas with different characteristics (closure areas, areas subjected to different fishing efforts, etc.) were performed (Schejter et al., 2008; Schejter et al, this workshop, Bremec et al., 2011). The smaller fraction of the fauna (not retained in the fishing nets) was also studied (Sánchez et al., 2011). Species richness of the area was found to be markedly increased due to epibiotic and endobiotic associations (Schejter & Bremec 2007, 2009; Lopez Gappa & Landoni, 2009, Schejter et al. 2011a,b, Schejter et al. 2012). Complementary, an inventory of fishes incidentally caught during trawling events added 24 fish species of benthic habits to the total richness of the area (Schejter et al., 2012). The source of data for the majority of these studies was the annual research surveys, developed onboard the INIDEP Research Vessels and also on board Fishery Vessels. Annual reports on invertebrate fauna composition at Zygochlamys patagonica fishing grounds could be found in INIDEP Technical Reports (e.g. Bremec et al. 2012). Based on all this information, we could compile a very complete list that up to date totalize more than 200 taxa that inhabit the benthic realm at Zygochlamys patagonica fishing grounds. This high richness registered in Argentine waters is due to the high productivity registered in this frontal area, one of the most productive ones in the SW Atlantic Ocean (Acha et al., 2004, Bremec et al. 2000).