Efeito de fatores ambientais na pesca costeira nos trópicos com rede de emalhe

Abstract

The variation of marine environmental factors modulates environmental seasonality and influence on diversity, fish catchability and that is directly related to yield in from fisheries. There is important to define patterns of variations to ensure the maintenance of stocks. Thus, the objective was to test if the seasonal pattern of rainfall and wind influences in structure of fish assemblages in tropical coastal and yield in gillnet fishing bottom. For this there were three samples during the rainy season and three in the dry season. It has been calculated: 1. Species and specimens number per net bid; 2. Average length per species per bid; 3.Catch per net bid; 4.CPUE with standardized effort: weight (Kg) / (net 1330 m * net bid hr); 5. Average wind speed (average of 6 hours per day: 3 hr per bid + 2 hr before + 2 hr after) (m/s); 6. Monthly precipitation sum (mm). The diversity was analyzed by abundance Whittaker curves, diversity profiles and Shannon index. Was used Principal Component Analysis (PCA) to analyze the relationship of more abundant species with environmental variables. Were collected 2.373 fish belonging to 73 species of 34 families, of whom 20 frequent and abundant species. The Whittker diagram indicated the rainy season as richer and more equitable than the dry season. The diversity profiles indicated that the rainy season was slightly more diverse than the dry season, even Student t-test for the diversity of Shannon did not detect significant differences between seasons. The univariate ANOVA showed a significant difference to factor weather station, with the rainy season having the highest average observed values. The factorial ANOVA indicated a significant difference for rainfall only. The chi-square (X2) indicated that winds of the northeast quadrant (NE) predominated in the dry season and the southeast quadrant (SE) in the rainy season. The PCA indicated the formation of three species groups, a group mainly related to wind speed, rainfall with another group and a separate one, a separate one with the largest number of species and varied environments. Thus, it was concluded that the seasonal pattern of rainfall and wind modulate the structure of assemblies of fish and fishery yields, with bottom gill net in tropical areas. Emphasizes that rainfall strongly affects the salinity and turbidity in coastal water. Thus, we suggest the analysis of salinity and turbity as complementary studies to assess the impact of environmental variations on the ichthyofauna structure.