Studies conducted on several freshwater lakes in East Africa, including the famous Lake Victoria, have concluded that the average size of the fish that inhabit them is decreasing steadily. The studies attribute this to the rising temperature of the water, which makes small fish more likely to survive than larger fish.
Aside from the ecological risks that this poses, the shrinking of these fish poses a pressing economic and social risk as well. In Uganda, fisheries account for 12.5 percent of agricultural GDP, and fish makes up half of the protein in the average Ugandan diet. As fish sizes decrease, many will lose access to their biggest source of protein.
To make matters worse, while the sizes of fish are decreasing, the population numbers are not rising to make up for it. In fact, the population may also decrease due to the fact that many of these lakes are shrinking over time as well. Mark Olokotum, one of the contributors to the lake studies, told Africa’s Inter Press Service (IPS) that “although rainfall in the East African region is expected to increase as a result of climate change, this gain may be offset by increased evaporation associated with increases in temperature”.
Another explanation for the decreasing size of fish is through artificial selection of years of fisheries operating on the lakes. Fishing vessels look for the biggest, meatiest fish that will fetch the highest price, sometimes tossing smaller fish back. Over time, being small becomes an evolutionary advantage for the fish, and their future generations become smaller and smaller. This is a common side effect of fishing all over the world, and could have the same disastrous effects on a much larger scale if left unchecked.
Where Uganda is uniquely affected is that it relies very little on aquaculture, that is to say farmed fish, preferring wild-caught fish. So, while other countries in the area can fall back to aquaculture, where regulating the temperature of the water is relatively easy, Uganda is stuck with the declining sizes and stock available to the nation’s people. Many fisheries and processing plants have shut down completely due to the shortages and high costs.
Dr. Justus Rutaisire, who leads aquaculture studies at Uganda’s National Agriculture Research Organization, believes that investment in science and technology by the Ugandan communities and government will be the key to bouncing back from this hardship. He told IPS that “if measures cannot be agreed and implemented quickly, then we are condemning those communities to death”.