Reproductive biology and morphometric characters of the Squid Loligo forbesi (Cephalopoda: Loligindae) in the Suez bay. Red Sea,Egypt

Abstract

Reproductive biology and morphometric variation of male and female Loligo forbesi were investigated from samples obtained from commercial catches in Suez bay. The samples were collected seasonally between 2005 and 2006. The results of sex ratio indicated that females outnumber males during peak periods of reproduction. Based upon morphological features of the gonads, three maturity stages were described in both sexes. Depending on the proportion of each maturity stages as well as various maturity indices (gonad somatic index, GSI and nidamental gland index. NG1) the spawning season was found to take place during spring and early summer. Sexual dimorphism is evident in L. forbesi, where the males grow more rapidly than do females and achieve larger sizes. The mean size at maturity was 106 and 104 mm dorsal mantle length (DML) for males and females respectively. Potential fecundity estimates were obtained by counting eggs and ova in the oviduct and ovary of mature females and were in the range of 4985 to 12427 (mean = 9633±1555). There was a weak relationship between ova number and mantle length but a reasonable positive correlation was reported. The ovaries of mature females contained eggs of various sizes, indicating that spawning probably occurs intermittently. Comparisons of external morphometric characters between males and females of L. forbesi indicated a high overlapping between the sexes. Sexual dimorphism was limited to few measurements,