Variation of the condition factor in teleosts captured as part of the fauna accompanying the seven-beard shrimp, Xiphopenaeus kroyeri fishery at Praia do Perequê, Guarujá-SP D. M. Araujo, K. R.O. Cordeiro, A. A. Almeida, J. L. Santos, M. M. Rotundo

Abstract

No matter how much the fishing effort is directed at a target species, there will always be the capture of other accessory species or “ bycatch ”. Part of this “ bycatch” is returned to the sea, due to lack of economic and/or technological interest, and is then referred to as disposal. Therefore, knowledge of the biological aspects of these species is necessary in order to measure the impact of fishing on them. 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 the species of Teleostei discovered by the seven-beard shrimp fishery, on Perequê beach, Guarujá-SP. Two samplings were carried out (Spring and Summer) using a local fishing vessel, equipped to capture Barbary shrimp. 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 identified and measured individually 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 species, where they were subjected to a linear regression to obtain the allometric coefficient (“b”), using the expression: K= Wt/CT ^b _. To verify the correspondence of the condition factor between the sample periods, a one-way analysis of variance (ANOVA) was applied, adopting the confidence interval (α = 0.05). In total, 28 species were captured, 15 in spring and 22 in summer, totaling 363 and 316 specimens respectively. Of these, only Isopisthus parvipinnis , Paralonchurus brasiliensis and Stellifer brasiliensis presented a sufficient number of specimens, in both periods, to carry out the analyses. The average K value was 0.010784 for I. parvipinnis , 0.630204 for P. brasiliensis and 0.030078 for S. brasiliensis . ANOVA demonstrated a significant difference for K between the study periods, with the Wt and CT values ​​being responsible for the variation. It is therefore clear that greater knowledge about the seasonal patterns of biological aspects of discarded species is also necessary to obtain the real impact of this fishing activity on the accompanying ichthyofauna.