Abstract:

Imported Artemia cysts (the Brine Shrimp) arc currently the readily available live starter feed to African catfish breeders in Uganda but are highly priced. In this study, the potential use of locally grown rotifers (Brachionus calyciflorus) as an alternative starter live feed to Artemia in the feeding of African catfish (Clarias gariepinus, Burchell, 1822) larvae was explored. African catfish larvae were cultured in experimental tanks under ambient hatchery conditions and tested on three experimental live starter diets; freshly decapsulated Artemia cysts, rotifer B. calyciflonis and a combination of the two on the third, fourth and fifth days to meet their exclusive requirement for live starter feeds during the first three days. A short period (3 days) of diet experimentation used in this study may have limited the lull understanding of growth performance with diet in larval African catfish, but it was nonetheless based on the practice by all commercial fish farmers in Uganda to provide a live starter diet for only two to tliree days following commencement of exogenous feeding of the African catfish larvae. Change in Total Length (TL) measurements of larvae was used as a measure of growth. Fatty acid profiles of sixday old larvae were determined using Gas chromatography-mass spectrometry (GC-MS) method and cost effectiveness of utilizing either Artemia or Rotifer starter diets computed. To explain whether different Artemia strains used as live starter feeds for African catfish larvae may impart different growth performance, three commonly used Artemia (USA - Artemia franciscana, Asia- Artemia salina and China Artemiastrain) were tested on two days old African catfish larvae. Feeding African catfish larvae on different Artemia strains yielded no significant differences in growth (F= 0.875, P=0.42) and survival (F=1.485; P=0.299). However, overall growth of Rotifer-fed African catfish larvae was significantly better than Artemia - fed larvae (F= 47.605, P=0.000). Noteworthy, was tire fact that catfish larvae fed on a mixture of Rotifers and Artemia grew faster (10.04±0.45 mm, P—0.000) than those fed on either rotifers or Artemia (Rotifer 9.04±0.58 mm, Artemia-8.78±0.54mm, P=0.147). Significantly higher composition of Arachidonic acid (AA), Docosahexaenoic acid (DIIA) and proportions of DHA/EPA and AA/EPA were recorded for Rotifer -fed larvae than for Artemia-fed larvae (AA, F=22.292, P=0.016 and DHA, F=28.740, P=0.011, respectively). These essential fatty acids play a significant role in the structural, physiological and functional development of larval fish and may explain the better growth recorded in this study. The combination of rotifers with Artemia was probably of an added advantage due to the large-sized Artemia that makes catchability easy. On the other hand, partial or total replacement of Artemia with Rotifer was more cost effective than using only Artemia. The results of this study recommend B. calyciflorus rotifers as alternative to Artemia in hatchery in raising African catfish larvae because they compete favourably with Artemia in fish larvae growth performance and are cost effective. However, utilization a combined diet of rotifers and Artemia as live starter feeds in African catfish hatcheries would provide added advantage in achieving better growth results of the fish.