W EANING FRY OF THE AFRICAN BONYTONGUE (H eterotis niloticus ) TO PARTICULATE DRY FEED DIETS
Ofori-Darkwah, P1. *, Adjei-Boateng1, D., Edziyie1, R.E., Agbo1, N.W. and Lund, I.2
1Department of Fisheries and Watershed Management
Kwame Nkrumah University of Science and Technology, Kumasi Ghana
2 Technical University of Denmark, DTU Aqua, Section for Aquaculture,
The North Sea Research Centre, DK-9850 Hirtshals, Denmark
E-mail:
princedarkwah@yahoo.com
Tel +233246140035.
A m ajor challenge to the commercial culture of Bony tongue (Heterotis niloticus ) is low larval survival rates due to lack of suitable weaning diets. This study evaluated the survival and growth performance of H. niloticus fry weaned at 40 days after hatching (DAH) to three locally formulated diets (D) of different crude protein content (CP); D1: CP-41%, D2: CP-43 %, D3: CP-45%, compared with a commercially available fry feed (Raanan) D4: CP-48%, and a group that was fed with live Artemia as a control. Eight hundred and ten (0.60 ± 0.17g ) H. niloticus fry raised in the laboratory on Artemia nauplii were randomly distributed into 9 (3x3) tanks with 54 individuals per tank. The 3 experimental diets were daily fed at 10% of total body weight/tank for 21 days. At the end of the trial, the mean weights (g±sd) of the juveniles were 1.00 ±0.58, 1.75±1.10, 2.00±3.20 for the 3 test diets, respectively and 1.80 ±0.20, and 3.60±0.20 for the commercial diet and the control, respectively. The survival rate differed significantly between the treatments (p<0.0001 ) with the control having the highest rate of (88.3%) followed by the commercial diet (21.6%) while the locally formulated diets had poor survival rates; 0.6%, 4.9%, 3.0% respectively . During co-feeding with Artemia nauplii the m ortality was very low (<7%) for all the test diets during the first 7 days, however mortality increased sharply from the second week when the fish were solely on their respective test diets. The results indicated that the fry of H. niloticus will require well balanced particulate diets to enhance growth and survival. Further investigations on the protein to lipid ratios will be experimented in subsequent trials to evaluate its effect on the survival and growth performance for this species.