Biologia reprodutiva e hábito alimentar do beijupirá Rachycentron canadum (Linnaeus, 1766), como base para o desenvolvimento da piscicultura marinha

Abstract

Cobia Rachycentron canadum is considered an excellent species for marine aquaculture. However, little is known regarding its biology in the coastal waters of Brazil. The aim of the present study was to describe the reproductive biology and feeding habits of cobia along the coast of Pernambuco state (northeastern Brazil). The work was carried out between February / 2004 and August / 2006, with samples collected from artisanal and sport fishing. Total length ranged from 42.0 to 141.0 cm (mean and standard deviation: 95.8 ± 19.8 cm) and total weight ranged from 0.4 to 29.8 kg (7.5 ± 4.3 kg). The type and time of spawning, length at fisrt maturity (L50) and fecundity was evaluated. Furthermore, it was analyzed the food strategy and the importance of each food item in the diet using the index of relative importance (IRI). Histological analysis of the 99 gonads (42 females and 57 males) evidenced the presence of mature females throughout the year. Length at 50% maturity was 69.8 cm of furcal length (FL) for females, with 100% of adult females in the length class of length above 90-100 cm FL. Batch fecundity ranged from 192,063 to 1,600,513 oocyte and the mean relative batch fecundity was 32.9 to 104.8 oocytes / gram of female weight. A total of 110 stomachs were analyzed (54 females and 56 males), 92 (83.6%) contained food items and 18 (16.4%) were empty. Bony fish were the main food item (IRI = 98.7%). The squirrelfish (Holocentrus adscensionis) and porcupine fish (Diodon sp.) were the most frequent prey itmes (30.7% and 8.2% IRI, respectively). Elasmobranchs, crustaceans and cephalopods were also present in small proportions (IRI < 1% for each). No significant differences in diet were found between sexes or size classes (zoological length: < or ≥ 69.8 cm; estimated L50 for the species). The present data demonstrate that cobia along the coast of Pernambuco state (northeastern Brazil) had a protracted reproduction throughout the year, but with peake between January and April, when the highest gonadosomatic index are verified for females and is a carnivorous predator with a preference for demersal bony fish, independently of the size and sex of the individuals analyzed.