Population characteristics of the swimming crab Callinectes amnicola De Rocheburne, 1883 (Crustacea, Brachyura, Portunidae) in the Qua Iboe River estuary, Nigeri
Journal Title: Aquaculture, Aquarium, Conservation & Legislation - International Journal of the Bioflux Society - Year 2011, Vol 4, Issue 3
Abstract
Aspects of the biology of Callinectes amnicola, from the Qua Iboe River estuary, south-eastern Nigeria, was investigated for twelve months from June 2008 to May 2009, with respect to its size composition and population characteristics. A total of 1,193 specimens were obtained comprising 508 males and 685 females with overall (1:1.35, χ[sup]2[/sup]= 26.26, 1 df, p < 0.05) and rainy season (1:1.2; χ[sup]2[/sup] = 2.17, I df, p <0.001) sex ratios in favour of females, while the dry season ratio of 1:0.84 was male-biased (χ[sup]2[/sup] = 11.44, 1 df, p <0.05). Carapace length (CL), carapace width (CW) and total weight (TW) of crabs were significantly (p < 0.05) influenced by sex, moult stage, colour morphotypes, and development stage. The crabs sampled were 26.6 to 87.0 mm CL (Mean ± S.E: 62.48 ± 0.23), 53.7 to 187.0 mm CW (124.5 ± 0.51) and 9 to 323 g (126.39 ± 1.43) and exhibited a high composition (80 - 90%) of adults. Males ranged from 14 to 323g and 78 to 175 mm CW, and females 9 to 293g and 54 – 187 mm CW, indicating sexual dimorphism in which males attain larger sizes than females (p < 0.05). The crabs were furtherclassified as juvenile or adult based on abdominal morphometry. The reproductive indices (gonadosomatic index and hepatosomatic index) were significantly higher (p < 0.05) in adult than in juvenile crabs. Crabs of the green morphotype were larger in proportion (59.31 %) and were significantly longer and heavier than other colour morphotypes (p < 0.05). Crab total weight and carapace length/width were higher (p < 0.05) in the dry months (November to March) than in the wet (April to October). The study reveals high internal variabilities in the size composition and population characteristics of C. amnicola inhabiting the lower reaches of the Qua Iboe River estuary, Nigeria.
Authors and Affiliations
James Udoh, Anthony Nlewadim
Keywords
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