Some Aspects Of The Biology Of Two Members Of The Family Cichlidae In Kaduna River Nigeria

Investigation into some aspects of the biology of Oreochromis niloticus (Peters) and Tilapia zillii (Gervais) were conducted between August 1966 and July 1967. Samples were obtained twice monthly during the period of the investigation from River Kaduna. The standard length of males 0. niloticus ranged from 6.5 to 26.0 cm while that of ferales ranged from 6.6 to 25.7 cm. The weight of the males varied between 11.0 to 592.1g while that of females varied between 29.0 to 593g. In T. zillii the standard length of males ranged from 7.0 to 23.0 cm while that, of females ranged from 9.0 to 21.8 cm. The weight of males varied between 16.0 to 480.5 gm while that of females varied between 13.0 to 240g. The length-weight regression analysis indicated negative allometric growth for both species. The mean condition factors for both species were found to be good throughout the period of investigation except, in the months of January and February where there were general fall in conditions. The fishes exhibited diverse feeding habits. 0. niloticus fed more on algae and diatoms than T. zillii which fed almost exclusively on higher aquatic plants. Chi-square test revealed that the sex ratio of • 2- niloticus did not deviate from the expected 1:1 ratio. In T. zillii there were more males than females.

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