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Article Information:
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 and O.A. Davies
Corresponding Author: Abowei Jasper
Submitted: 2009 August, 27
Accepted: 2009 September, 14
Published: 2010 January, 10 |
Abstract:
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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=3.89
yr-1 and exploitation rate (E)= 0.7495. The exploitation rate (Emax) that gives maximum relative yield-perrecruit
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 (L∞) and asymptotic length (L4) 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∞=61.8, K=1.71yr-1, C= 0, WP = 0,
to=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.
Key words: Callinectes amnicola, mortality, exploitation rate, recruitment, Okpoka Creek, Nigeria,
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Cite this Reference:
J.F.N. Abowei, A.D.I. George and O.A. Davies, . Mortality, Exploitation rate and Recruitment pattern of Callinectes amnicola (De Rochebrune, 1883) from Okpoka Creek, Niger Delta, Nigeria. Asian Journal of Agricultural Sciences, (1): Page No: 27-34.
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ISSN (Online): 2041-3890
ISSN (Print): 2041-3882 |
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