Seletividade de captura e sustentabilidade das redes de emalhe na pesca da viola (Loricariichthys anus) no sistema lagunar Mirim-Mangueira, RS

Abstract

The objective of this study was to determine the selectivity of gill net, used in capturing the viola, resulting in more efficient economic and sustainable perspective in the Mirim and Mangueira Lagoons, RS. Viola (Loricariichthys anus) is the kind of higher incidence and economic importance caught by artisanal fishermen in the region, has high economic value for the quality of their meat. Fishermen operating in the region complain that the quantity and the average size of fish caught are decreasing, resulting in the reduction of inventories over time. The local fishing activity is characterized as artisanal fishing, which is the only source of income for many families. The fishing gear developed in the region is the gillnet, where the most used are the meshes of 60, 70, 80, 90, 100 and 110 mm between opposite knots. According to Instruction No. 2 of 09/02/2004 IBAMA / SEAP, the minimum mesh size allowed in the area is 80mm to 90mm for Mangueira and Mirim Lagoon. A suitable fishery management implies that the fishing gear to capture adult fish (mature), allowing smaller (immature) to escape, thereby ensuring the possibility of reproduction and renewal of the population. There were 5 repetitions in each pond. In Mangueira lagoon were used two sets of 15 gillnet, 5 mesh gillnet 60mm and 70mm mesh nets 5 and 5 x 80 mm mesh. In Mirim lagoon were used two sets of 10 gillnet, with 5 x 60mm mesh and 5 mesh gillnet 70mm, in both experiments the mesh sizes were interspersed, the fighters were placed in predetermined places by fishermen. Fish caught in each mesh were counted and submitted to biometric evaluation, a sample of 20% of the total catch was taken to the Ichthyology of UFPEL laboratory for further analysis. For selectivity calculations we used the method of Holt (selectivity of the two mesh) and for statistical evaluation the BiosEstat 5.0 software. The results suggest the use of mesh 70 mm between opposite knots, which provide greater economic gain and increased average size of fish caught, giving sustainability activity.