Effect of size on spawning of Imbaw, <i>Anodontia edentula</i> (Linnaeus, 1758)

Abstract

The effect of shell size to spawning of imbaw, Anodontia edentula was examined. A total of 120 clams with shell length ranging from 34.90 to 68.20 mm were collected. Basing on shell length, 3 class sizes were used to group these clams, namely: < 45 mm, 45-50 mm, and > 50 mm. Thirty-five percent of the clams had shell length of < 45 mm, 21.7% in the range of 45-50 mm, and 43.3% had shell length of > 50 mm. Overall result showed that a high percentage of the clams in the range of 35 to 50 mm responded to spawning induction. Result showed that 41 (98%) of the clams in class size < 45 mm spawned. Twenty-six (100%) of the clams in 45-50 mm spawned and 31 (60%) spawned in class size > 50 mm. A mortality of 2 occurred among the broodstock and had shell lengths of > 50 mm. Among the clams induced to spawn, males predominated in the sample. Only 1 case of hermaphroditism was observed in < 45 mm and no females were observed to spawn. The only immature male in class size < 45 mm has a GSI value of 22.3. The mean GSI value of the 19 immature clams in class size > 50 mm was found to be 23.9 (±7.62).