Abstract
Oreochromis variabilis Boulenger (1906) is an indigenous and critically endangered fish species of Lake Victoria. It is among the species targeted for stock enhancement and restoration in Kenya. Such mass stock enhancement requires simple and easily applicable techniques to maximize its larviculture. This study investigated the growth potential of O. variabilis from fry to fingerling stages using diets formulated from locally available feed materials during the rearing period. Fish fry reared on formulated diets incorporating Rastrineobola argentea Pellegrin and Caridina nilotica Roux as protein source and cassava as basal feed gave higher growth and survival rates than those maintained on plankton live feed alone. There were significant differences in the final mean lengths and weights of fish fed the three treatment diets. Diet 3 gave significantly higher final mean lengths and weights than Diets 1 and 2. Growth rates of fish fry fed diets 2 and 3 regimens were significantly higher than those fed diet 1. The best food conversion ratio and condition factor were maintained in fry populations reared on Diet 3. The study concluded therefore that, viability of larviculture of O. variabilis using simple formulated diets may be achieved, and that this result provides an important breakthrough in the propagation of its seed stock for mass culture towards stock enhancement and restoration to marketplace. Key words: Oreochromis variabilis, endangered species, rearing techniques, larviculture, stock enhancement, restoration.
Highlights
Since the beginning of fisheries in Lake Victoria, two native tilapiine cichlids, Oreochromis variabilis (Boulenger 1906) and O. esculentus (Graham 1929), were the main target of the local fishermen
Source of experimental fry, stocking size and density. Fry used in this experiment were obtained from a timed pond hatchery spawn of ten one-strain females and five holotype males collected from Oki resource dam, located in the southern Lake Victoria Basin, close to Kenya Marine and Fisheries Research Institute (KMFRI) - Sangoro Aquaculture Research Station
Results of Length weight relationships (LWRs) of larvae in all treatments were described by a negative allometric growth (b < 3) (Table 4)
Summary
Since the beginning of fisheries in Lake Victoria, two native tilapiine cichlids, Oreochromis variabilis (Boulenger 1906) and O. esculentus (Graham 1929), were the main target of the local fishermen. Their disappearance from the Lake Victoria waters may be attributed to alterations in habitat ecology, competition for niche resources or predation of their juveniles by the introduced species mainly the predatory Nile perch, Lates niloticus (Linnaeus 1758). Some remnant populations of O. variabilis are found in some small water bodies (SWBs) within the Lake Victoria Basin and these can provide brood stock for successful breeding in order to restore and conserve the species
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