The Morphology, Abundance, Size and Sex Distribution of Callinectes amnicola (De Rochebrune, 1883) from Okpoka Creek, Niger Delta, Nigeria

J.F.N. Abowei ； A.D.I. George

《Current Research Journal of Biological Sciences》 2卷1期 (2010/01) Pp. 27-34

並列摘要

The morphology, abundance, size and sex distribution of callinentes amnicola from Okpoka Creek was studied for one year. Callinectes amnicola carapace is broad, moderately convex, ending laterally in a strong spine, preceded on the lateral margin by 9 distinct teeth. The length of the lateral spine is twice or more than that of proceeding tooth. The carapace width is about twice or slightly more than twice its length (2.0-2.3 times). Carapace upper surface is roughly granular. Epibranchial ridges are without distinct inflection in middle, almost straight. Four sub-median frontal teeth are well developed and are usually half or more than half as long as the outer pair. The chelipeds are strong, unequal and pincers with distinct ridges. As with other Portunids, the last (fifth) walking leg with propondus and dactylus is broad and flat, paddle-shaped to accommodate swimming. The crab species exhibit obvious sexual dimorphism. Male blue crabs have a T-shaped abdomen readily distinguishable from both juvenile and adult stages of the female. Female may be identified due to their triangular or rounded aprons. Immature females have triangular shaped abdomen with fused segments. However at the terminal or pubertal molt, the final ecdysis and onset of sexual maturity, the mature female abdomen becomes broad and rounded. It is also easily identified by its body color, which is generally described variously as olive-brown molted, and as blue or bluish with pink and pale legs. The highest number of male crabs was recorded in station 6 (24.50%) followed closely by station 5 (22.66%) then station 2 (15.97%), station 4 (15.76%), station 1 (10.77%) and station 3 (10.33%). Similarly, the females were most abundant in station 6 (23.90%), followed by station 5 (22.92%), station 4 (21.89%), station 2 (14.81%), station 3 (9.0%) and station 1 (7.47%) the least in abundance. The distributions were similar for both males and females. The size classes 30-39.99mm and 40-49.99mm were the highest in number for both sexes. The least number was recorded for size class 70-79.99mm. A total of 13,785 specimens of Callinectes amnicola comprising 45.5% males and 54.5% females were recorded. The crab's sizes ranged from 1 lmm to 74mm (males) and 12 to 76mm (females). The total weight ranged from 1.79g to 146.72g (males) and 1.17-151.62g (females). The largest size for the males (74mm, 146.72g) and females (76mm, 151.62g) were observed in December. The smallest size of the male (11mm, 1.79g) and the female (12.0mm, 1.17g) were recorded in October. The fairly higher body dimensions showed by males and females of C. amnicola in Okpoka is an indication that the creek is productive and environmentally stable.

並列關鍵字

Callinectes amnicola ； morphology ； abundance ； sex and size distribution ； Okpoka Creek and Nigeria