Idade e crescimento da caraúna azul, Acanthurus coeruleus (Bloch & Schneider, 1981) (Perciformes: Acanthuridae) capturada no litoral norte de Pernambuco

Abstract

The blue tang, Acanthurus coeruleus, is distributed in tropical and subtropical waters. It is an important member of the trophic guild of large mobile herbivores, presenting a considerable social organization in great or small schools of domination in territorial systems at coral reefs. It is found in the coastal areas of the Northeast Brazil. A. coeruleus is caught in the fishing traps as bycatch fauna of the saramunete fishery and is considered as one of the most exported ornamental species in Brazil. The aim of the present study was to estimate the growth parameters for Acanthurus coeruleus in Pernambuco coastal areas. A monthly sample collected in 2007-2008 was analyzed. From artisanal and commercial fishing the sagittae otoliths were obtained, removed, cleaned, embedded in plyester resin, sectioned, mounted on microscopic slides and analyzed under stereomicroscope using transmitted light. The micro and macroincrements were read and the counts were adjusted to the models of von Bertalanffy (VBGF), Generalized von Bertalanffy (VBGF Gen.), Gompertz, Logistic, and Schnute using the likelihood and the Akaike Information Criterion (AIC), to choose the model providing the best fit. Counts were conducted in 610 individuals ranging from 3.75 to 41 cm in total length; there were no significant differences in the weight-to-weight ratio for the separated sexes (ANCOVA, t-value = 103,716, p = 0,000). The readings of 261 were carried out for the macrostructures in which the IAPE was 3.69%. Eleven otoliths were read for microincrements and the coefficient of variation (CV) was 3.063%. The relative marginal increment (MIR) showed significant difference (Kruskal-Wallis; p = 0.000266) suggesting that ring formation occurs once a year mostly in November. Of the 261 slides read, the maximum age was 13.6 years and minimum was 0.22 years, there were significant difference between the parameters Bertalanffy (VBGF) (L∞ = 42,00 cm; k = 0,173; t0 = -0,724). VBGF displayed the best fit comparing to the other models for the macro and microstructures when separated sexes are considered.