Sex ratio of the sea-bob shrimp Xiphopenaeus kroyeri of the coast of Ilhéus, Bahia, Brazil

Abstract

The object of this research was to conduct a study of the sex ratio of X. kroyeri in the three main trawling areas on the Ilhéus coast in order to better understand the species population structure. The monthly sex ratio per class and total length (mm) were analyzed, so as the proportion of young and adults in space and time. Monthly hauls lasting 30 minutes were conducted between November 2003 and February 2005 at three sampling stations located 16 m deep. We sampled 19,559 individuals, being 11,291 males and 8,268 females. Males and females were grouped into classes of total length (mm), and unimodal distribution were usually observed. The amplitude of the total length of males was of 20 mm to 110 mm and that of females, 20 mm to 140 mm. The sex ratio was 1:1 (í"¡² = 2.39, p>0.05). In the analysis of sex ratio by size, males were more prevalent in classes below 100 mm and females at 100 and 110 mm. Juveniles were present in all months, but there was an increase in abundance during June-July (winter) and September-October (spring). The young were more abundant in areas of the Airport and Santo Domingo, located next to the two largest estuaries in the region. Water transparency was the only abiotic variable correlated negatively with the abundance captured.