Why there is a notable increase in fish diseases

Dr Christopher Aura

Dr Christopher Aura is the director in-charge of fresh water systems research at the Kenya Marine and Fisheries Research Institute.

Photo credit: File | Nation Media Group

Dr Christopher Aura is the director in-charge of fresh water systems research at the Kenya Marine and Fisheries Research Institute (KMFRI). He spoke to Stanley Kimuge on the status of the fish industry

Paint for us a picture of the current situation in the fish industry?

Our annual production of fisheries and aquaculture stands at about 150,000 metric tonnes (MT), a decline from 250,000 MT in 2000. This decline is due to changes in the environment, particularly because of the quality of water. There has also been increased cases of over-fishing through use of bad nets that catch fingerlings, thus depleting stocks.

Of the 150,000 MT, Lake Victoria leads with 115,000 MT, followed by aquaculture that produces some 24,000 MT while the Indian Ocean 14,000 MT. This production leaves us with us a deficit of 400,000 MT.

Farmers are complaining about a rise in fish diseases, what’s the cause?

Diseases have been there but as the quality of water deteriorates and methods of farming change, an upsurge must be recorded. Notable diseases include fin rot that mainly attacks cage fish because farmers are putting many fish in one place. Ideally, a cage should have 80 fish per cubic metre.

Thus, because of the overcrowding, there is increased competition for space leading to injuries and when they have wounds, it is easy for fungi, virus or pathogens to enter into the flesh causing diseases.

Fish deaths were also reported recently in sections of Lake Victoria in Siaya, Homa Bay and Kisumu. This was because of a rise in water levels in the lake. And because the cage fish is kept in shallow water,  water from below with low oxygen reached the cages leading to the deaths.

How is climate change affecting the fish industry?

Climate change manifests in terms of floods and increased temperatures. First, high temperatures lead to low oxygen levels in aquatic environment reducing breeding areas for fish thus hurting population.

Second, flooding tends to damage the breeding areas and hurts fish catches because of increased water volumes and turbulences.

Lastly, due to climate change, cases of pollution have risen as water becomes scarce affecting sanitation. Pollution kills fish.

What can be done to increase fish production?

First, there is need for quality water for the survival of fish. A fish pond must have an inlet and outlet. The recommended oxygen levels in the water should be above 5 milligrams per litre (mg/per litre). One must also go for healthy brooder (mothers) because the healthier the brooder,  the better the fingerlings.

When it comes to feeding, the feeds should have a good crude protein level. Keep records so that when you notice there is a problem, you are able to address it and lastly, network with other farmers.

What should the fish farmer do to survive the increased importation of fish, especially from China?

We import fish because we have a deficit amid high demand. More people are consuming fish because it has high nutritional value (Omega 3, which is good for brain development.) Second, fish has no side effects. Farmers can cope by producing more fish through aquaculture. We can also increase production through stocking and restocking our dams and other water sources with quality fingerlings. With enough fish we will be able to compete favourably with imports.

You recently opened a fish genetics and genomics laboratory at the University of Eldoret, what does this mean for local fish production?

We have two main types of fish species; the tilapia and Nile perch. Tilapia accounts for three to five per cent, dagaa (omena) 57 per cent followed by the Nile perch at 36 per cent.

This has put pressure on tilapia, the most loved. With this laboratory, scientists will now be able to conduct DNA extraction that will help us to use other species to identify those we can farm in ponds.

For instance, in the Indian Ocean, we have a species known such as rabbit fish which most people eat but they don’t farm. Research will help us to diversify the species of farmed fish.