Lake Victoria's fish stocks are struggling to keep up with demand. For instance, stocks and catches of Nile perch have reduced, from 340,000 tons in 1990 to about 251,000 in 2014. Though there's no official figure, from our discussions with fisheries stakeholders we know that the tonnage on the Kenyan side now stands at about 99,000.
Nestled between Tanzania, Uganda, Kenya, Burundi and Rwanda, millions of people depend on the lake. In 2010 there were about 42.4 million and it's projected that by 2030 there will be almost double - about 76.5 million. About 3 million people rely directly on fisheries for food, and about 30 million from the East African region rely on them for their livelihoods.
There's also international demand for the Lake's fish. Catches of leading commercial species - Nile perch and Nile tilapia - are now primarily caught for export, mostly going to Europe and Asia.
These challenges to natural fish stocks are compounded by over-fishing and illegal and unregulated fishing activities.
In our research, we argue that cage aquaculture or farming, where fish are raised and harvested in a netted enclosure in an existing water system, could provide an alternative to how fish are produced. This could increase fishery production without damaging wild stocks.
Cage farmers in Kenya - where most of Lake Victoria's cage activity is based - currently produce about 40,000 tons of fish per year. By comparison, 99,000 tons of wild fish were landed in Kenya in 2016.
Catching wild fish, with nets or lines, and cage farming are the only two ways fish are harvested from the lake. But for both production mechanisms to remain in harmony, there needs to be proper regulations on cage farming. These will improve coordination and collaboration between everyone involved, and ensure that the harvesting of fish is done without harming the environment.
Cage farming is when a netted enclosure is suspended in an aquatic environment - like a sea or lake. This enclosure houses fish or other aquatic products.
In the case of Lake Victoria, it's been there for about 13 years and involves private sector players, development agencies - like the EU funded cage farming project - and small-scale fisheries.
Today cages are concentrated along the Kenyan side of Lake Victoria. And the industry is quickly gaining ground. Currently, there are about 4,000 cages of varying sizes, but mainly of 2 by 2 by 2 square metres in the lake under 60 different owners. Most of the cages are individually owned (62%), while groups (38%) own others.
As an alternative to traditional pond culture systems on land, cage farming can overcome some of the conventional fish farming constraints. This has helped it to grow in popularity.
There's very high production of fish per unit volume of water
Relatively less investment is needed per unit of production compared to pond or land culture. The cost of starting up a cage industry - including cage material, feeds, fingerlings, security, a boat for accessing the cages, and labour - can range between US$4,300 to US$590,000. There is a huge variation in cost because the cages, source of materials and size of the operations vary greatly.
Use of existing water bodies reduces water demands on land and also means the industry is less affected by drought.
Ease of relocation of cages from one site to another and there's also ease of accessibility for operational practices, such as feeding and cleaning the nets.
Ultimately, the profitability of cage farming depends, among other things, on which species is cultured, management level, input costs, and market prices.
But cage farming does have its challenges - and so it's vital that proper policies are in place to address these.
Farmed fish may also escape and interact with other fish in the wild which can spread disease and parasites.
These impacts can, in turn, decrease local catch of wild fish, creating a conflict between cage culture and fishermen. This is already a delicate situation because of competition over lake space.
It's important that proper regulation is put in so that cage culture reduces poverty, provides food and boosts the income of the fishers, while reducing pressure on capture fisheries.
Guidelines by the East African Community for cage farming already exist, but these must be enforced and other regulations developed. These include:
Moving the cages to deep waters (about 10 metres depth) where there's more oxygen and the flow of water helps them to "self-clean"
Farmers must have access to mapping tools so they know the right place to install their cages. This will protect navigation of other boats, and natural fish breeding zones and fishing areas to avoid conflicts.
Cleaning cage netting regularly to avoid fouling and clogging.
Use of floating feeds to avoid excessive accumulation of uneaten feeds.
Develop business plans for cage enterprises to track their operations, monitor progress, and make adjustments for improved performance.
Involve a good number of vulnerable communities - like women - by giving them start-up capital
Insuring operations against risks and losses.
With this proper regulation, Lake Victoria's fisheries stand a good chance of increased production without damaging wild stocks or the environment.