Mortality, Exploitation Rate and Recruitment Pattern of Callinectes amnicola (De Rochebrune, 1883) from Okpoka Creek, Niger Delta, Nigeria

J.F.N. Abowei ； A.D.I. George ； O.A. Davies

《Asian Journal of Agricultural Sciences》 2卷1期 (2010/01) Pp. 27-34

並列摘要

The motality, exploitation rate and recruitment pattern of Callinectes amnicola from Okpoka creek was studied from January-December 2007. Total mortality (Z) value was Z=5.19 yr^(-1), M=1.30 yr^(-1), F=3.89yr^(-1) and exploitation rate (E)= 0.7495. The exploitation rate (E(subscript max)) that gives maximum relative yield-per-recruit was 0.4890. The exploitation rate at which marginal increase occurred in the relative yield-per-recruit was 10% of its value at E=0, whereas (E0.1) was observed to be between 0.4684. The exploitation rate (E0.5), which, corresponds to 50% of the virgin (i.e., the unexploited stock) relative biomass-per-recruit was 0.3129. The mean ratio of length-at-first capture (Lc) and asymptotic length (L∞) was 0.21, while that of natural mortal (M) and growth rate (Kyr^(-1)) was 0.82. The recruitment pattern showed all year round recruitment with two peaks (one major and the other minor). The parameters obtained were L(subscript ∞)=61.8, K=l.71yr^(-1), C= 0, WP = 0, t0=0. The percentage recruitment values for the different months were: January (4.29%); February (5.45%), March (7.47%); April (15.50%); May (20.57%); June (15.68%); July (8.77%); August (7.40%); September (0.43%); October (1.23%); November (13.21%) and December (0.00%). C. amnicola from Okpoka creek die more due to human exploitation than natural death, thus experiences excessive fishing pressure. This implies that the level giving maximum sustainable yield has been overshot. There is therefore the urgent need to check the exploitation of C amnicola in Okpoka Creek for its sustainability.

並列關鍵字

Callinectes amnicola ； mortality ； exploitation rate ； recruitment ； Okpoka Creek and Nigeria