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Aquaculture CRSP 21st Annual Technical Report
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143
Techniques for the Production of Clarias gariepinus Fingerlings as Baitfish
for the Lake Victoria Nile Perch Longline Fishery

Social and Economic Aspects/Product Diversification/Experiments (10NSR5)
Final Report

Charles C. Ngugi
Department of Fisheries
Moi University
Eldoret, Kenya

James Bowman
Department of Fisheries and Wildlife
Oregon State University
Coravallis, Oregon, USA

Bethuel Omolo
Fisheries Department
Government of Kenya
Sagana, Kenya

Abstract

Clarias gariepinus is probably the most widely distributed fish in Africa. It can endure very harsh conditions by using its accessory air-breathing organ, it is omnivorous, and it grows quickly. As a result, this species has a high potential for aquaculture. In recent years Clarias have also become important to the Lake Victoria Nile perch fishery, which is of enormous economic importance in Kenya, Uganda, and Tanzania. Although trawling for Nile perch is practiced by some fishers, it is not legal on Winam Gulf, a main fishing zone in Kenya, so some fishermen have resorted to longline fishing, using fingerling-sized Clarias as bait. A quick survey of fishermen indicated that they bait from 100 to 1,000 hooks per boat per day, and if one assumes there are 50 boats, the demand in Kenya will be between 5,000 and 50,000 Clarias fingerlings per day. At 300 fishing days per year, this equates to an annual demand of between 1.5 and 5 million fingerlings. The present supply of fingerlings is intermittent, however, partly because most methods of capturing wild fingerlings have been banned. Fishermen therefore find themselves in a difficult situation because they need the bait at an affordable price to be able to continue fishing. At the reported selling price of 5 to 8 KSh per fingerling, the industry could be worth up to KSh 40 million annually (or about US$0.5 million). An estimated production cost of about 0.1 KSh per fingerling, farm-based production of Clarias fingerlings could be a highly profitable business for fish farmers.

Research on the artificial propagation of
Clarias spp. has provided a host of options for farmers, ranging from highly controlled induced spawning to many variations of partial control to the unpredictable but easy natural spawning. However, survival of larvae to the fingerling stage remains problematic, regardless of the propagation method used. Factors identified as contributing to poor survival include cannibalism, lack of adequate cover, and predation by insect larvae and other aquatic organisms.

This report discusses four sets of experiments being conducted at the Chepkoilel Campus of Moi University, Eldoret, Kenya, with the objectives of determining the best percent shade cover for nursery ponds, the best stocking densities, and the best culture periods for rearing
Clarias larvae, and the best of several alternative live foods (rotifers, copepods, Artemia) to offer larvae during the nursery phase. Two experiments are being conducted in hapas suspended in 300 m2 earthen ponds and two are being conducted indoors in 30 liter glass aquaria. The durations of these experiments will be from 21 to 30 days. Preparatory work began in May 2003 and the research is currently underway. All experimental work is expected to be completed by the end of 2003. Full results will be reported in student theses (M.Sc.) coming out of Moi University in early 2004.

Introduction

Clarias gariepinus is probably the most widely distributed fish in Africa (Skelton, 1993). It can endure very harsh con
ditions by using its accessory air-breathing organ, is highly omnivorous, and grows quickly. This fish has high potential for aquaculture. Research into the culture potential and the artificial propagation of this fish began in the 1970Ős. (De