Benthic community in two Patagonian Scallop Reproductive Reserve Areas, SW Atlantic Ocean

LAURA SCHEJTER; ESCOLAR MARIANA; BREMEC CLAUDIA

Florianopolis

Workshop; 19th. International Pectinid Workshop; 2013

Characterization, identification of invertebrates and monitoring of the benthic community at the Patagonian scallop fishing grounds in the SW Atlantic Ocean have been continuous activities developed by technicians, researchers and students working at the Benthos Laboratory (INIDEP). Moreover, a very unusual (but undoubtedly helpful!) situation is given by the fact that the baseline condition of this benthic community in the year 1995 (before Fishery) is well-known and documented (Bremec and Lasta, 2002). In this benthic community, more than 150 invertebrate species have been recorded until moment, being sessile or epibiotic near 50% of them. A conspicuous assemblage of invertebrate species that characterizes this community remained constant between 1995 and 2011 (Bremec et al., 2012). The present contribution aims to characterize the benthic community in two Patagonian Scallop Reproductive Reservations Areas (closed to commercial fishing since 2009, Res.Nº5, CFP, 2009). Comparative benthic community samples from the surrounding areas were also analyzed in order to compare taxa composition and richness. The results here presented correspond to the situation in October 2011. Material and Methods The 2 main study areas are currently known as Management Unit F (MUF, ex MU9) and Management Unit G (MUG, ex MU 10), and are located between 43º02.43’ and 44º11.82’ S and between 59º35.77’ and 60º55.11’W (MUF) and between 44º11.97’ and 45º15.38’ S and between 59º35.99’ and 60º55.11’W (MUG). Samples for the characterization of the benthic community inside and outside closed areas (Patagonian Scallop Reproductive Reservation Areas – RRF and RRG) were collected during the Patagonian scallop stock assessment cruise onboard the RV “Miss Tide” in October 2011. This vessel is equipped with bottom otter trawls with booms, with an horizontal opening of 22 m and mesh size of 140 mm. Samples (Vol:10L) were obtained from total catch on the deck. In total, 38 samples were studied (see Table below). Presence-absence data, MDS analysis and SIMPER test were used to characterize differences and similarities between the studied areas. Results and Discussion Recorded species in all sampled areas were previously known from preceding stock assessment cruises and are common taxa of the benthic community (Hydrozoa, Porifera and Bryozoa remained as major taxa for this study). Results of taxa richness (range) by sample and total are given in the Table below. SIMPER test showed that the following taxa constituted the main assemblage (95%) in the 2 areas: MUF: Zygochlamys patagonica, Sterechinus agassizii, Porifera, Idanthyrsus armatus, Gorgonocephalus chilensis, Ophiacantha vivipara. MUG: Zygochlamys patagonica, Sterechinus agassizii, Porifera, Ophiacantha vivipara, Gorgonocephalus chilensis, Magellania venosa, Idanthyrsus armatus, Actiniaria, Adelomelon ancilla, Alcyonium sp., Chaetopterus sp. RRF was characterized by a very high proportion (near 95% in biomass) of scallops and just few by-catch organisms per sample. RRG was characterized by a high proportion of scallops, but also Porifera, Adelomelon ancilla, Actinostola crassicornis, Sterechinus agassizii, Magellania venosa and Terebratella dorsata. Taxa recorded inside the closed areas (RRF and RRG) wouldn´t be different to the general composition of the main area according to MDS analysis. Although minimum number of samples required for the majority of the taxa to be registered was not reached inside the closed areas (N=8 according to Bremec et al., 2000), this is the first attempt to monitor benthic community composition inside Patagonian Scallop Reproductive Reservation Areas, and provides a very useful baseline information. Monitoring in time of these particular habitats and the comparison of fished vs. non-fished areas will help to better understand the structures and processes of these benthic communities, aiming to improve management strategies. Area Nº of samples Nº taxa/sample (range) Total taxa richness FGF 12 10-27 49 RRF 3 12-19 25 FGG 20 12-32 57 RRG 3 21-27 34 Bremec et al., 2000. Arch.Fish.Mar.Res. 48: 295-303. Bremec and Lasta, 2002. Bul.Mar.Sci. 70: 89-105. Bremec et al., 2012. Inf. Inv. INIDEP 10, 14pp.