A MALE fish in a cage/pond is capable of serving only three females. Contrary, a fish farmer won’t have anticipated harvests, especially in terms of quality products.
Again, when male-female ratio is done in the pond, reproduction should be four batches consecutively, and then let the parents go for a two- month vacation in separate ponds.
Vacation is a must to let parents regain the energy they have wasted throughout the reproductive term, said the Assistant Hatchery Operations Supervisor at the Son Fish Farm, in Jinja city of Uganda, Mr Joseph Nsenga.
He made the revelation during the recent tour of the Tanzanian officers and fish farmers of Ilemela district in Mwanza region (Tanzania), at the Centre in Kampala city. The tour was coordinated by the Tanzanian Embassy in Uganda and Lake Victoria Fish Organization (LVFO), aimed at knowledge, skills and experience sharing in fish farming issues.
“Single reproduction batch takes 21 days after the eggs are matured in a fish. The female spits out the eggs and lets the male give sperm for fertilization. That is why they both need a vacation since they jointly invest much energy for the process,” said Mr Nsenga.
Usually, reproduction for a pair of fish couples takes place in at-least two years. Then the parents have to rest for life. Soon after the hatching, the fingerlings are to be shifted to another pond, giving a chance to parents for further reproduction.
For profit gain purpose, the Son Fish Farm applies ‘Sex Reversal’ technology for mass production of male fish, whose demand in markets is high compared to females ones. Normally, the fish is created with no sex; instead, becoming male or female is influenced by environment it leaves in.
“We therefore serve the figerlings with feeds rich in male harmonies to let the majority be males. That is the environment we set to make this possible. Males are growing bigger than females, a reason behind their high demand in markets,” he said.
Again, male fish growth and weight gain is made possible within a short time compared to females, a reason behind the marketability.
Female fish are small in size compared to male due to various reasons, including the fact that it has minimal time to feed itself, especially during the time of reproduction.
During the process, the female has for some time swallowed its eggs after they have been fertilized by male sperms, so as to have the heat that engineers timely hatching. It also swallows the eggs for security purposes of its coming fingerings and therefore spends a couple of days with no feed, said Mr Nsenga.
After ‘sex reversal’, males for reproduction are to be chosen and taken at the site to join the females who should be there first few days back, waiting for males.
It was further noted that anecdotal research shows that once males don’t find females in a reproduction site, then they boycott. After the selection of reproduction males at Son Fish Farm, the rest fingerings are left in a pond for three weeks until they have one gram weight.
Then they get shifted to juvenile cages in Lake Victoria. They have to spend two months in juvenile cages to gain 20 grams and once again get shifted to grow- out cages.
“In grow out cages we feed them intensively as they have to be harvested after six months, with 500 grams and above. We are dealing with only tilapia,” he said.
To avoid fish diseases, Mr Nsenga told the visitors that before shifting the fish, the outlet water pipes of the next pond should be set open to dry it for disinfection.
Then the water is to be refilled to clean out the disinfection substance and let the pond stay empty for three days. If the pond is for reproduction activities, it should first be refilled with sand, whose particles serve as egg lay sites.
“Parents fish do dig up holes on sand for eggs accommodation, a move that also eases fertilization process by males,” he said.
The Tanzanians had time to visit the cages in Lake Victoria, with Tanzanian Ambassador in Uganda, Dr Aziz Mlima inviting the Farm Operators to visit Tanzania for intensive training to fish farmers.
The company’s Managing Director, Mr Robert Osinde, expressed his willingness to continue exchanging skills and technologies with Tanzanians, in an effort to increase the fishing sector’s contribution to the economy of both countries. Among the technologies are how best to shift the fingerings from the hatching area to another place, so as to engineer the quick reproduction among fish parents.
He stressed that skill exchange is of most import since fish farming involves huge investments, hence, no need for Tanzanians to invest but earn nothing simply because they have no ‘how to do it’ knowledge. The countries are endowed with Lake Victoria, whose water is quality and has required temperature to support fish farming, he said.
“Fish farming has lots of benefits, including job creation as we have 136 staff here. Economically, the markets are everywhere, mostly Kenya and Congo DRC. We are able to produce 60 metric tons per cage, two times in a season and we have got about 78 cages,” he said.
However, availability of fish feed is still a serious challenge facing Ugandans, since the quality ones are not locally produced due to especially lack of the additives.
