Possible lessons on rapid assessment of fish kills in cages in Lake Victoria, Kenya for informed decision making

Abstract

Cage aquaculture is quickly expanding in the African Great Lakes Region, with the potential of boosting fish output and acting as a source of food security, poverty reduction, job and wealth creation. However, the proliferation of fish cages in Lake Victoria has come along with sporadic fish kills especially in the shallow zones of the lake in specifically the months of September to November each year and whose documentation is key for future references in case such occurrences reoccur. This paper indicates and discusses results from a rapid assessment of recent fish kills in the years 2021 and 2022 and sheds some light on the possible causes of the fish kills using standard methods and proposes mitigation measures moving forward. Low dissolved oxygen levels (≤ 4.0 mg L^-1) instigated by increased eutrophication and upwelling are noted as the main causes of the fish kills. The application of good aquaculture practices for fish cage culture husbandry, application of guidelines as well as fast-tracking and enforcement of regulations will promote sustainable cage farming in such lacustrine systems.