Abstract:

The importance of the small pelagic fish species in most African Great Lakes (AGL) has increased, with mukene on Lake Victoria contributing >45% of the commercial landings and >60% of the fish biomass in
2015. However, mukene is currently harvested at less than 30% of its total biomass using the traditional kerosene pressure lamps and encircling net (lampara) technology, yet studies indicate that short lived species (e.g. mukene) can sustainably be harvested up to 60% of their total biomass. The National Fisheries Resources Research Institute (NaFIRRI) secured funding under the National Agricultural Research Organisation’s Competitive Grants Scheme (NARO-CGS) in 2014 to implement a study "Improving light attraction technologies for enhanced harvest of mukene on Lake Victoria". The main objective of the study was to develop a commercially viable mukene harvesting technology for improved food and nutritional security as well as enhanced household incomes among artisanal mukene fishers on Lake Victoria, Uganda. The study investigated the effect of light colour, source, and intensity on attraction and concentration of mukene in the shallow inshore (<20 meter depth), mid-island (>20-40 m) and deep open water zones (>40 m) of the lake. The performance of different light settings (floating, surface and submerged) using a low cost rig made from locally available materials for easy adoption by artisanal mukene fishers was also evaluated. The effect of lunar phases on mukene harvest and proportion of by- catch were explored through analysis of commercial catch data collected for a period of one year (2016 -
2017) from industrial rigs operating at Kiyindi in Buikwe district. The green (3.6 ± 0.9 Kghr-1) and white (2.3

± 0.8 Kghr-1) light colours harvested high catch rates (>2Kghr-1). Generally, the catch rates increased with intensification of light intensity and varied with light source; the solar bulbs harvesting higher catch rates (12.1 ±2.9 kg hr-1) than the traditional pressure lamps (7.2 ±2.9 kg hr-1). Surface lights harvested higher catch rates (2.0 0.4 Kghr-1) than other light settings. Although, catch rates were higher during the third quarter (4,322 Kgday-1) and new moon (4,167 Kgday-1) of the lunar phase, the proportion of by-catch was highest during full moon. The proportion of by-catch, especially juvenile of Nile perch and Nile tilapia, was higher in the Napoleon Gulf than deep open waters of Nkata. Mukene fishing in the shallow inshore areas especially closed bays should be avoided since it negatively impacts on the sustainability of the Nile perch and Nile tilapia which use these habitats as their breeding and nursery grounds. Furthermore, adoption of solar light attraction technologies (SoLAT) using white and green lights in the deep open waters of the lake where high quantities of mature mukene and less by-catch of Nile perch and Nile tilapia is highly recommended. Since SoLAT is a new technology, there is urgent need to formulate a policy to guide its use
in harvesting mukene on Lake Victoria. However, the public should be sensitized on the implications this new technology to avoid conflicts that may arise among the different fisheries. Further research to determine the sustainable fishing effort for mukene stocks in the lake, to avoid a similar scenario of stock decline in the Nile perch and Nile tilapia fisheries due to unregulated fishing effort, is highly recommended