Variation of the condition factor in Trichiurus lepturus caught in floating seine fishing, on Toque-Toque Pequeno beach, São Sebastião-SP L. S. Bernal, G. C. Stabile, M. S.C. Matos, M. M. Rotundo

Abstract

Even though it does not have targeted capture, swordfish ( Trichiurus lepturus ) has important economic value for artisanal fishermen on the north coast of the state of São Paulo. They are captured by different types of artisanal, industrial and sports fishing. Therefore, knowledge of the biological aspects of this species is necessary in order to measure the impact of fishing on it. The condition factor (K) indicates the degree of health of an individual, being related to the environmental conditions and behavioral aspects of each species. The present study seeks to analyze the seasonal variations of this factor in Trichiurus lepturus captured by floating seine fishing, at Toque-Toque Pequeno beach, São Sebastião-SP. Four samplings were carried out (May to August/2016). After capture, the organisms were euthanized with clove oil and then preserved on ice and transported to the laboratory. In the laboratory, the fish were measured in terms of total length (TL) using an ichthyometer (accuracy of 1 mm) and weighed with the aid of an analytical balance (accuracy of 0.1 g). The condition factor (K) was obtained after logarithmizing the weight (Wt) and length (CT) values ​​of each specimen, where they were subjected to a linear regression to obtain the allometric coefficient (“b”), using the expression: K= Wt/CT ^b _. To verify the seasonal variation of the condition factor, CT and PT, a one-way analysis of variance (ANOVA) was applied, with the Tukey test being used subsequently. An analysis of covariance (ANCOVA) was also carried out, seeking to highlight seasonal differences between the correlation (CTxPT), adopting the confidence interval (α = 0.05). In total, 118 specimens were captured, 33 in May, 31 in June, 28 in July and 26 in August. The average values ​​of K, CT and PT were 3.96x10 ^-06 , 837.6±122.2 mm and 406.7±211.3 g, respectively. Seasonal variations were observed for K (p=4.47x10 ^-69 ), CT (p=0.001373) and PT (p=0.000158), however the CTxPT ratio did not vary. It is therefore evident that greater knowledge is needed about the seasonal patterns of biological aspects of species captured by fishing, in order to contribute to the adequate management of the local fishing stock.