SOUTH-SOUTH COOPERATION PROGRAMME
PROGRESS ON THE THREE EXPERIMENTS,
GENETIC SELECTION, SEX REVERSAL AND FEED VALIDATION AT ONAVIVI IAC
PERIOD: JANUARY –MARCH 2015
CHIEF FISHERIES BIOLOGIST
The Onavivi IAC is one of the largest Government centres, for fish breeding, fingerling distribution and feed production in the Northwest region of Namibia. The centre is currently carrying out three experiments, under the SSC project activities. These experiments are Genetic selection, sex reversal and fish feed validation. The aim of the report is to highlight briefly on what has happened on each activities during the period mentioned above.
1. Sex reversal
The objective experiment is to identify the effective levels of hormone treated feed that will results in the production of 98% mono sex fish. The experiment started with the conditioning of Broodstock, mating, egg collection, incubation, and nursing. The experiment is being carried both indoor and outdoor conditions. The figures bellow illustrates the materials and methods used for the sex reversal experiment.
Preparing the pond for cages:
The pond was dried and poles where set in for anchoring the cages.
Figure 1. Pond preparation to set in cages for Broodstock conditions and matting
Figure 2. Cages set with Broodstock condoning and mating (ratio 3:1)
Figure3: Egg collection
When the eggs are collected, they are sorted into different stages of development. The eggs are then transferred to the incubators into the hatchery, as illustrated in the in the figure below.
Figure 4: Eggs collected and sorted in different stages of development
Figure 5: Incubation at Onavivi hatchery
Figure 6: Nursery stage, sex reversal indoor experiment, Onavivi IAC
Figure 7. Nursery cages, sex reversal outdoor experiment, Onavivi IAC
Figure 8. Sampling the outdoor experiment, Onavivi IAC
2. Genetic selection
The objective of the Genetic selection is to enhance the production of quality seeds but the use of different fish strains of Oreochromis andersonii. The three strains are from Kavango, Omusati (Cuvelai system) and Zambezi regions and are all under conditioning stage at Onavivi IAC. There after the mating will start, egg collection, incubation and then nursery. The pictures below shows the cages where the different strains of Oreochromis anderstonii are being conditioned.
Figure 9. Cages where the three strains are being conditioned
3. Feed validation
The aim of the experiment is to validate the quality of imported floating feed and the locally produced sinking feed with respect to the growth of Oreochromis andersonii, both at fingerling stages until they reach the marketable size. The experiment will be conducted in indoor and outdoor conditions. The mono sex fingerlings for the feed validation are so far being collected and conditioned. Although there is a challenge of getting the required quantity and size of mono sex fish, the process is slow, but progressing.
A diet of 42%CP for both floating and sinking are used in the plastic tanks, to assess the growth performance of three spot tilapia under plastic tanks, as illustrated below.
Figure 10. Plastic tanks used for the feed validation experiment
To assess the growth performance of three spot tilapia, until it reaches market size, cage culture is used as means of culture system. A diet of 32%CP for both floating and sinking will be used. The diagram below shows the cages set in the cage platform at Onavivi reservoir.
Figure 11. Cage platform set in the Onavivi Reservoir for feed validation
Figure 12. Cages set in the Onavivi reservoir for feed validation
Under the South South Cooperation project several equipment has been acquired with the aim to analyse the nutritional composition of the feed. However due to the limited space (laboratory) where the equipment needs to be installed to be used for analysis was not possible. As a result the feed samples were sent to the local laboratory for analysis. The laboratory is not suitable, as it is too small and does not have all the required platforms to install the equipment. However, the Directorate of Aquaculture will see to it, if the budget allocation for 2015/2016 can assist in releasing funds for the renovation of the laboratory at Onavivi IAC. The picture, below show the layout of the current small laboratory with the acquired equipment.