Fecundity and Population Structure of Cockles, Anadara antiquata L. 1758 (Bivalvia: Arcidae) from a Sandy/Muddy Beach near Dar es Salaam, Tanzania

Abstract

The fecundity and population structure of the cockle, Anadara antiquataL., from sandy/muddy intertidal habitats in the intertidal of Ocean Road beach was examined from January to December 2001. A. antiquata is hand harvested, for domestic consumption, mainly by women and children, with the empty shells sold to traders. The sex ratio from combined data of all classes deviates significantly from 1:1 with the ratio of females to males increasing significantly above 41 mm shell length. Hermaphrodites were also observed in this size range indicating a protrandric hermaphrodite situation with males maturing earlier than females. Fecundity increases with an increase in shell length, with a mean of 1,652,000 (+/- 562,000 [or 40%] SE) eggs per female and correlated significantly with shell length and whole live weight. Two peaks were observed from length frequency analysis, one dominated by juveniles and other with mature A. antiquata. The slope b from length-weight relationship for A. antiquata was 2.7134 (n = 1,951) indicating isometric growth.

Keywords: cockles, Anadara antiquata, hermaphrodite, fecundity, intertidal zone, ocean road

West Indian Ocean Journal of Marine Science Vol. 4 (1) 2005: pp. 77-84