Benjamin Tsirilaza

New Doctor on DIDEM in Madagascar

Bio-ecology and fish exploitation in the Betsiboka Estuary, northwest Madagascar

Benjamin Tsirilaza defended his thesis on March 25, 2024 at the University of Toliara, Madagascar.

Abstract and power point presentation:

The study of fish populations and fisheries in the Betsiboka estuary has attracted considerable scientific interest, due to the crucial role of this environment in the life cycle of certain fish species, its social and economic importance, and the threats posed by the expansion of human activities. Located in the north-west of Madagascar, the country's largest estuary faces challenges such as marked variations in the hydrological regime, hypersedimentation, increased fishing pressure and an area of internal population migration. This situation raises concerns about the state of fish communities and the future of fishing activity in the area and surrounding coastal zones. Thus, the need for sustainable fisheries management is becoming more pressing if long-term exploitation of fishery resources is to be envisaged. A bio-ecological and fish exploitation study was carried out in the Betsiboka estuary between March 2021 and October 2023, with the aim of providing scientific information to guide sustainable fishing. The study focuses on three major aspects: bioecology, fishing activity and stock assessment, as well as the current level of resource exploitation. The methodology adopted involves the creation of an observatory for small-scale fishing in the Betsiboka estuary. This observatory implements a system for monitoring the physico-chemical quality of the water, the fish population, fishing practices, and the daily measurement and weighing of catches. This methodological approach should provide information on the seasonal and spatial dynamics of physico-chemical water parameters and their impact on the fish population. It also aims to deepen understanding of the characteristics of resource exploitation by small-scale fisheries, and to generate knowledge on growth parameters, stocks and biological reference points related to fish exploitation in the Betsiboka estuary.

Keywords: Betsiboka estuary, water quality, fish diversity, traditional fishing, fish stock, northwest Madagascar.