Inland fisheries are among the world’s most important sources of dietary protein, income and employment. The world fish production increased from 137.3 million tonnes in 2006 to 154.0 million tonnes in 2011 primarily through aquaculture, the fastest growing food sector in the world. While capture fisheries has stagnated or declined through over fishing at about 90 million tonnes, aquaculture production has increased from 47.3 million tonnes to 63.6 million tonnes between 2006 and 2011 (FAO, 2012). In particular, Uganda’s aquaculture production based on earthen ponds has also grown from 5,000 t in 2004 to 95,000 t in 2011 (FAO, 2012).
The huge increase in world aquaculture production is largely due to utilization of nature water bodies for aquaculture production. Uganda’s total annual fish production is about 550,000 t, 90% of which comes from five large lakes (Victoria, Kyoga, Albert, Edward and George) with a combined surface area of 34,506 km2. Only 5% of the annual production comes from over 160 smaller water bodies (sizes ranging from < 1 to 200 km2) and another 5% from aquaculture. Half of the 160 small water bodies occur in western Uganda but their potential fish production is largely unknown. Small water bodies include reservoirs and small lakes with an area of less than 10km2, small ponds, canals, irrigation canals, swamps and small seasonal inland floodplains. Increased fish trade has led to substantial capital investments directed towards fisheries of the large lakes with 19 fish processing plants on the Ugandan parts of lakes Victoria and Albert.
The worldwide per capita fish consumption increased from an average of 9.9 kg in the 1960s to 18.4 kg in 2011 but in Africa it is only 9.1 kg (10kg in Uganda which is below the FAO recommended of 25 Kg and will decline further as the population grows at 3.5% population per annum (FAO, 2012). The country has a significant potential for increasing fish production from other sources and biomanipulation of presently underutilised waters is one option. There is evidence that some fisheries such as the Nile perch fishery in Lake Victoria is faced with over fishing with fishers targeting smaller fish and many fish processing plants running well below capacity while others have closed business (Balirwa, 2007).
In order to attain the FAO recommended per capita fish consumption of 25 kg, Uganda requires at least an additional 330,000 t of fish annually for its population of 34 million (UBOS, 2012). Current aquaculture production meets only 10% of the fish gap, and more aggressive efforts are required to efficiently increase sustainable production. The country has a significant potential for increasing fish production from other sources and utilization of the presently underutilised small waters is one option to supply additional sources of fish to meet the gap. Small water bodies could supply additional sources of fish to meet the gap of 330,000 tonnes.
Enhancement of fisheries can be achieved via several biomanipulation mechanisms including shifts in harvesting regimes, improvement in water quality, and stocking/restocking programs. Biomanipulation is a widely accepted tool for improving fisheries production in unproductive lakes and water quality in nutrient-rich ones (McQueen, 1988; Hansson et al., 1998); however, its success demands a thorough understanding of the trophic interactions and links in food webs.
In Uganda, successful fish species introductions were carried out in lakes Kyoga and Victoria in the 1950s and 60s (e.g., Kudhongania, 1991; Balirwa et al., 2003), although the ecological consequences were not considered and are now challenges to management of these lakes (Ogutu-Ohwayo, 1990; Balirwa et al., 2003). Similarly, in Lake Victoria, fishery yield increased from 100,000 to 500,000 t following expansion of the Nile perch stock (Pringle, 2005) and the lake now yields about 1,000,000 t (LVFO, 2008). Other successful introductions in Africa include Limnothrisa miodon (kapenta) into Lake Kariba from where it invaded several lakes in central Africa e.g., lakes Itezhi-Tezhi and Kivu (FAO, 1981).
A study of nine crater lakes, Efitre (2007) found highly variable growth rates among introduced Tilapia zillii populations, influenced by fishing pressure, water quality characteristics and population density. Many of the lakes are now characterized by stunted (stocked) tilapia. The mechanisms underlying the stunting vary across lakes and are thought to include size-selective fishing on large individuals as well as high levels of intra-specific competition in lightly fished lakes (Efitre, 2007). A study of the fishery status of some of the restocked lakes (Chahafi and Kayumbu) by Kamanyi et al. (2006) confirmed that regular restocking was needed to sustain the fisheries. In addition to increasing fish production, the small water bodies of western Uganda also offer opportunity to conserve some fish species that are endangered in the large water bodies.
Uganda’s population continues growing rapidly (3.5%) and so is the demand for fish with the immediate fish gap of 330,000 tonnes. This demand cannot be met by the current level of capture fisheries and aquaculture production. In Uganda, most fisheries developments have been directed towards increasing fish production from the large lakes and integrated aquaculture systems of various kinds. The potential of the small water bodies has largely been neglected, although they appear to present the best hope for the near future. The more than 160 small water bodies in Uganda are clustered within predominantly rural areas inhabited by poor communities and are of importance to their livelihood by providing water, an immediate source of protein, and employment. Stakeholder Research Priority settings by NaFIRRI and frequent calls by the local governments and communities to revamp the stocks or advise on utilization of these lakes have not been addressed. DFR continue to receive requests from the private sector to invest in cage culture in some of the small lakes. This project therefore seeks to provide a scientific basis for developing technologies and tools for informed utilization of the various water bodies to enhance fisheries productivity in western Uganda.