Contribuições à gestão pesqueira da Laguna dos Patos, RS, Brasil

• Autor(a) principal: Ceni , Gianfranco
• Data de Publicação: 2015
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da PUC_RS
• Texto Completo: http://tede2.pucrs.br/tede2/handle/tede/6057
• topic: ZOOLOGIA; ICTIOLOGIA; PEIXES - RIO GRANDE DO SUL; PESCA; PROTEÇÃO AMBIENTAL; GESTÃO AMBIENTAL; CIENCIAS BIOLOGICAS::ZOOLOGIA

Fish resources of the Patos Lagoon have been drastically reduced since 80's, when overfishing with harmful fishing gear affected the stocks. In the last decade there have been major breakthroughs regarding the conservation of the lagoon estuary, however, freshwater region still suffers with the lack of a specific management plan. In that sense, to contribute to fisheries management different tools were applied: initially, analyzing the dynamics of fishing activity and subsequently, studying the age in growth of two fish species by a new methodological approach. The results of the artisanal fishing, which evaluated the activity times, distances, fishing gear used and the captured fish species (identification and biometrics), revealed the existence of two fishing strategies: forbidden mesh (MPR) (mesh size 20-30mm) and allowed mesh (MPE) (mesh size 35-80mm). Even recording 31 species (MPE = 27 and MPR = 24), both strategies revealed selectivity in their catches (ANOSIM R = 0.8613, p<0.0001). The MPR gillnets were harmful as they captured small individuais (97% <260mmCT) and therefore below the size of first maturity for most species, including the target species Loricarüchthys anus (60.91 % of the total catch), over which these fishing equipment are used during the closed season. However, the target species in the MPE were larger (Mugil liza, Genidens barbus and Micropogonias furnieri) and gillnets were not used during the closed season. The aggressive use of MPR reveals the need of effective conservation measures. In this context, emerges the need of studies to assess the conservation status of these exploited species. This predicate served as support for the development of a new methodology to determine the age in length. Retrocalculated measures from lapilli otoliths of two marine catfish species (Genidens barbi+s and Genidens genidens) were used in von Bertalanffy equation adjusted for capture and recapture data.In this model, the retrocalculated measure from the previous ring represented the moment at capture, while the next ring represented the moment at recapture. This approach allowed the analysis of the growth in age at individual levei, followed by two subsume vias: by the average of the growth parameters (L. and k) and by the minimization of residuais in Average Total Length, once estimated through individual growth curves. Both methods were able to represent the species' life history. However, the model allowed that paired measurements of ali otoliths could be grouped and analyzed as a single individual. This way, the growth parameters were directly obtained, corresponding to the best fit from a methodological point of view (error dissolution) and legitimacy. The quality of information about the local fishing dynamics resulted in a series of proposals to resource management and when associated with the development of a new growth in age methodology was able to strengthen reasonable contributions to fisheries sustainability.