Aquaculture continues to be an important sector in the African economic development agenda. To further strengthen and diversity the industry, in response to the requests by farmers, there is an essential need to increase the number of cultured species in Africa. The African bony tongue, Heterotis niloticus has a huge potential for culture. However, the major challenge hindering its commercial production is its high larval and fry mortality, which have been linked to inadequate nutrition and handling stress. The aim of this work was to share the experiences acquired in handling fry and juvenile H. niloticus and to contribute to the knowledge base for managing its hatcheries. It summarizes the best practices for managing water quality, collecting larvae/fry, feeding preferences, transporting fry, and the beneficial effects of using the green water technique in H. niloticus larviculture. To understand the conditions under which the species thrives, the breeding behaviour and water quality in larval nests and surroundings were was monitored during the breeding season. Additionally, a feeding trial was conducted with H. niloticus fry from 6 to 27 DAH (days after hatch) using six feeds: Artemia nauplii; rotifers; 50% Artemia nauplii and 50% rotifers (w/w); egg custard, egg yolk and compared to fry that were not fed. Moreover, a simulated transportation trial was conducted for four different periods 24, 48, 72 and 96 hours with mortality and water quality (temperature, DO, pH and ammonia) monitored before and after transportation of fish inside the bags. Finally, fry were reared in two rearing media: “clear water” and “green water” with H. niloticus fry at 8DAH for 6 weeks. The results indicate that Artemia nauplii is best live feed organism for H. niloticus larviculture after yolk sac absorption. Additionally, there was deterioration in the water quality and a gradual increase in mortality with increase in transportation periods. Fish reared in “green water” systems, had a 20% higher survival rate and showed better growth. These studies on H. niloticus larviculture have given insights into some best practices in terms of husbandry techniques, transportation strategies and feed preferences at each growth stage. Additionally, the green-water rearing approach demonstrated high practical efficacy in the growth and survival of Heterotis niloticus fry; farmers can easily adopt this and we continue to work on ways to improve hatchery practices for the species.
Key words: Heterotis niloticus, nutrition, transportation, fry, green water technique.