Growth and reproduction of the Nile perch,Lates niloticus,an introduced predator,in the Nyanza Gulf,Lake Victoria,East Africa |
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Authors: | Nicholas F. Hughes |
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Affiliation: | (1) The Queen's College, Oxford University, Oxford, England;(2) Present address: Alaska Cooperative Fishery Research Unit, Arctic Health Research Building, University of Alaska Fairbanks, Fairbanks, AK, 99775, U.S.A. |
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Abstract: | Synopsis Length-frequency data suggest Nile perch, Lates niloticus, from the Nyanza Gulf grew to a total length of 9 cm by age 118 days and 23 cm by age 287 days. A modified von Bertalanffy growth curve t = 1.35·L(1-e–K(t-to)) with the parameters L = 93.1, K = 0.272 and to = 0.046, is suggested to describe growth up to 5 years of age and the relationship t = 1.35·(31.96 + 7.681t) for fish aged 6 years and above. Length-weight relationships were = 0.0234·-gt2.74 for fish between 7 and 15.9 cm total length, = 0.0151·2.94 for fish between 16 and 45.9 cm total length, and = 0.0023·3.44 for fish between 46 and 120 cm total length. Male Nile perch first matured between 50 and 55 cm total length when they were probably 2 years old; female Nile perch first matured between 80 and 85 cm total length when they were probably 4 years old. Small males were common, large males were rare, with the reverse holding for females. Sex change, from male to female, is a possible explanation for this size dimorphism. |
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Keywords: | Growth rate Length-weight relationship Maturation Sex-ratio Spawning Sex-change Protandry |
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