Out of the over 20 fish factories in Uganda, only 15 are still operational. And more could close, leaving hundreds jobless.
trueUntil World Environment Day, June 5, in a campaign, Save Lake Victoria, Vision Group media platforms will run investigative articles, programmes and commentaries highlighting the irresponsible human activities threatening the world’s largest fresh water lake.
By Mathias Mugisha
More fish factories are likely to close, leaving many fishermen and workers jobless. Out of the over 20 fish factories in Uganda, only 15 are still operational.
In Jinja district, two of the four factories have already closed down. All the factories are also operating below capacity because there is no fish.
Overfishing, catching immature fish, environmental degradation and pollution on Lake Victoria is killing the Nile perch (Latesniloticus), which forms the backbone of commercial fishing.
The young fish are starving and suffocating to death. The National Fisheries Resources Research Institute (NaFIRRI) predicts doom if the problem is not solved.
Records from NaFIRRI indicate that microorganisms in the lake, which the young fish feed on, are also dying. This is caused by the floating algal bloom on the lake that is poisoning both the fish and cuts off oxygen supply to marine life.
Elias Muhumuza, a research technician at the institute, says Nile perch needs enough space and dissolved oxygen more than other types of fish.
The lake is dying along with fish due to over fertilisation (eutrophication) — a process by which a water body becomes rich in dissolved nutrients from fertilisers or sewage, thereby encouraging the growth and decomposition of oxygen-depleting plant life like algae and resulting in harm to other aquatic lives.
Algal blooms are as a result of water pollution, usually caused by untreated waste from industrialisation, urbanisation and agriculture. This causes
a phenomenon that is experienced in some bays of Lake Victoria like Kitubulu and Murchison Bay.
Decomposition of dead algae and other organisms consumes much oxygen thus affecting the stability of the aquatic ecosystem.
“The result from the above scenarios is that the fish will die or will be under stressful conditions (due to lack of oxygen and food), meaning that they will not reproduce, grow well and hence reduced stocks.
"Many young Nile perch stay in shallow waters near the shores to avoid strong wind and being eaten by bigger Nile perch. Nile perch is dying young because the organisms the fish feed on also die,’’ explains Muhumuza.
Records from NaFFIRI show that the Nile perch has declined from an average of 1.2 million tonnes between 1999 and 2007, to about 0.8 million today. While mukene has increased from about 0.4 million to one million tonnes over the same period.
Other groups like tilapia and haplochromines (nkejje) have increased from 0.3 million tonnes to about 0.6 million tonnes.
“The increase in the smaller fish species is attributed to the decrease of the Nile perch, which preys on them. Once the number of predators goes down, its prey increases,’’ explains Muhumuza.
Currently, mukene accounts for about 70% of Lake Victoria biomass, overtaking nkejje, which previously accounted for 80% of the lake biomass before Nile perch was introduced.
The Nile perch was introduced into Lake Victoria from Lake Albert in the 1950 and 1960s for sport fishing. The Nile perch can weigh up to 250kg with an average length of a mature fish, averaging 121–137cm (48–54 inches), although many fish are caught before they can grow this large.
Although the introduction of Nile perch was an ecological disaster that has led to the extinction of the indigenous fish species, it increased fish stocks in the lake 10 times, according to NaFFIRI.
The Nile perch was introduced along with two other tilapia species to boast the indigenous tilapia stocks in Lake Victoria, which had declined.
According to Dr. Dismus Muhumuza, the head of Aqua Culture Research at NaFIRRI, the Nile perch was brought with four foreign tilapia species namely; Oreochromis niloticus, Tilapia zillii , Tilapia rendalli and Oreochromis leucostictes.
These species competed with the native tilapia species of Oreochromis variabilis and Oreochromis esculentus as the Nile perch hunted both of them with its high appetite directed at nkejje.
Today records from NaFIRRI show that Oreochromis variabilis is rare, while Oreochromis esculentus is extinct.
However, the Nile perch stimulated the establishment of large fishing companies and boosted sport fishing tourism in the region, with Murchison Falls as one of the best fishing destinations in the world.
Every year, a group of anglers from all over the world converge there, hook out Nile perch, weigh the fish and take their pictures with the catch before releasing the fish back into the water.
But now, the tide has turned against the Nile perch with man as its greatest enemy threatening its existence and the livelihood of the over 30 million people in East Africa, who depend on Lake Victoria.
“If this trend continues, more factories will have no choice, but to close. There will be no fish left to sustain the factories.’’ Muhumuza adds.
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