Abstract
The malacofauna bycatch of sea-bob shrimp Xiphopenaeus kroyeri (Heller, 1862) trawl fisheries on the coast of Sergipe was studied for 5 years. The malacofauna bycatch considered was obtained in nine oceanographic sampling campaigns carried out between May 1999 and June 2003 in 18 stations distributed in six transects along depths of 10, 20 and 30 m. A total of 2,669 individuals of mollusk belonging to 54 species were captured on the 18 sea-bob shrimp trawl stations carried out along the coast of Sergipe. The considerable richness of mollusks was composed by 19 families and 31 species of gastropods, 12 families and 19 species of bivalves and 2 families and 4 species of cephalopods. The highest abundance were observed at stations 13 (373 individuals) and 16 (685 individuals) that represents the lowest depth (10 m) and the richness was higher at stations 15 and 12 (17 and 11 species, respectively) both located at the highest depth (30 m). Cephalopods had high frequency of occurrence being collected in all the stations and by far the most abundant group with a total of 2,488 individuals captured. On the other hand, gastropods (with 142 individuals found in 83.3% of stations) and bivalves (about 1% of the individuals collected) contribute with a much smaller percentage of individuals captured. Lolliguncula brevis (Blainville, 1823) was most representative cephalopod in number and frequency of occurrence. Arcidae, Conidae, Muricidae and Strombidae were the families with the higher number of species in the trawl-fishery. Among bivalves, Pitar arestus (Dall & Simpson, 1901) and Spathochlamys benedicti (Verrill & Bush [in Verrill], 1897) were the species with higher frequency of occurrence. Although the considerable sample effort and a number of mollusks captured as bycath, the richness estimators indicated that the species richness could increase with additional sampling effort in the study area. The present study expands the taxonomic alpha knowledge on the mollusk bycatch of sea-bob shrimp trawl fisheries on the northeastern coast of Brazil. However, it is of crucial importance to assess urgently the negative impacts of the sea-bob shrimp trawl fisheries on the benthic community of the entire coast of Brazil.
Highlights
The present study provides important insights regarding the composition of the mollusk fauna on the continental shelf off the state of Sergipe, Brazil, for which few data have been published far
A total of 2,669 individuals belonging to 54 mollusk species were captured at 18 Atlantic seabob trawl stations along the coast of the state. This total was represented by 19 families and 31 species of gastropods, 12 families and 19 species of bivalves as well as two families and four species of cephalopods
The following taxa were not identified on the species level due to the poor state of preservation of the shells and/ or the fact that they were juveniles: Aplysia sp., Siratus sp. and Strombus sp. (Gastropoda); Chama sp., Chlamys sp., Corbula sp., Ostrea sp. and Spondylus sp. (Bivalvia); Loligo sp. and Octopus sp. (Cephalopoda)
Summary
Shrimp trawl fisheries constitute an activity of considerable economic importance on the coast of Brazil (Paiva-Filho & Schmiegelow, 1986; Mendonça & Barbieri, 2000; Braga et al, 2001; Paiva et al, 2001; Branco, 2005; Santos et al, 2006; Santos & Silva, 2008; Rodrigues et al, 2015; Maia et al, 2016). The bycatch of shrimp trawl fisheries has a considerable richness of invertebrates (Graça-Lopes et al, 2002a; Branco & Fracasso, 2004; Branco & Verani, 2006b), such as cnidarians, echinoderms, mollusks and other crustaceans (Braga et al, 2001; Paiva et al, 2001; Graça-Lopes et al, 2002a, b; Branco & Fracasso, 2004; Branco & Verani, 2006b; Belz et al, 2018)
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