Populational biology of three Penaeidae shrimps (Decapoda) in the Curuçá estuary on the northern coast of Brazil

Abstract

Sex ratio, population structure, and relative growth of Farfantepenaeus subtilis (Pérez-Farfante, 1967), Litopenaeus schmitti (Burkenroad, 1936), and Xiphopenaeus kroyeri (Heller, 1862) were studied in the Curuçá estuary, State of Pará, northern coast of Brazil. Samples were collected bimonthly from July 2003 to July 2004 using a wing trawl net. Each shrimp was identified and weighed, carapace length was measured, and sex was determined. We obtained 4,818 specimens of F. subtilis, 732 specimens of L. schmitti, and 608 specimens of X. kroyeri. Mean carapace length and weight were 11.95 mm and 1.29 g for F. subtilis, 15.32 mm and 3.67 g for L. schmitti, and 12.78 mm and 0.97 g for X. kroyeri, respectively. The sex proportion (males/females) was 0.8 for F. subtilis, 0.7 for L. schmitti, and 0.6 for X. kroyeri, with significant differences (P<0.05) for the three species studied. Farfantepenaeus subtilis and L. schmitti had positive allometric growth, while X. kroyeri had negative allometric growth. For F. subtilis two important recruitment periods were observed. The largest period occurred in March, and the other, less intense, began in September. For L. schmitti, recruitment occurred in July and in March. Xiphopenaeus kroyeri did not occur in November, with recruitment in January. Results show the importance of the Curuçá estuary in the development of these shrimps, and the information obtained is important for future management plans for its capture in this area.