Temporal variation in the reproductive pattern of blood cockle Anadara antiquata from Pakistan (northern Arabian Sea)

Sex ratios, size frequency, and reproductive patterns of blood cockle Anadara antiquata were studied from Sonmiani and Phitti Creek, Pakistan, from May 2004 to April 2005. At both sites, the overall sex ratio was significantly in favor of females. The population of A. antiquata at Sonmiani consisted of cockles of 31-80 mm in size and that at Phitti Creek of 21-100 mm in size; however, the majority of specimens were of 51-70 mm in size at both sites. Four stages of gametogenesis were identified in male and female cockles: 1) developing, 2) ripe, 3) spawned out, and 4) resorbing. No hermaphrodites or specimens with undifferentiated sex were found in the present study. The gametogenic activity in males and females occurred year-round, with greater intensity during January to March and low activity in December at both Sonmiani and Phitti Creek in female cockles, as indicated by low gonad index values of females in these months.