Ichthyofauna bycatch of sea-bob shrimp (Xiphopenaeus kroyeri) fishing in the town of Porto Belo, SC, Brazil

Abstract

The activity of artisanal fishing for the sea-bob shrimp, using the method of motorized dragnet with rings, has been practised on the Santa Catarina coast, where it generates jobs and income, and helps keep the traditional Azorean cultural tradition alive, since 1960. With the aim of analyzing the quality and quantity of the ichthyofauna bycatch, two trawls were carried out per isobath (10-20-30 m), seasonally, between November 2009 and August 2010 (i.e. summer, spring and winter), for 20 minutes each, at an average speed of two knots, and the bottom water temperatures and salinities recorded. The captures totalled 10868 fish (208.34 kg), distributed among 31 families and 62 species, with a fish/shrimp ratio of 5.19/1 kg. The most abundant family was Sciaenidae (86.13%), followed by Batrachoididae (2.70%) and Trichiuridae (2.44%). The diversity and evenness indices presented similar patterns of variation, the highest values occurring in spring at 30 m and the lowest in winter at 20 m. Cluster analysis led to the creation of four groups; one of them small and dominated by the Sciaenidae Stellifer brasiliensis, S. rastrifer, Paralonchurus brasiliensis, Isopisthus parvipinnis and Larimus breviceps. The young of this and other species, which are of little or no commercial value, along with tiny shrimps and other macroinvertebrates that enter the dragnets, are thrown back into the sea, usually dead. Besides the negative impact on the food chain, this continued practice could exacerbate the situation of artisanal fishermen even further, with the gradual, future decline of these resources.