ECOSYSTEM-BASED ASSESSMENT OF THE MALINDI-UNGWANA BAY PRAWN FISHERY USING ECOLOGICAL INDICATORS

Abstract

The study aimed to generate information that will contribute to development of an Ecosystem based approach to fisheries management (EAFM) of prawn resources in the Malindi-Ungwana Bay, Kenya. A comprehensive ecosystem-based approach is required to holistically assess and manage fisheries resources and their associated habitats. The study identified and assessed ecological indicators based on the objectives of sustainability of harvests, biodiversity conservation, and maintenance of habitat quality. Data analysed were sourced from; the Fisheries Department‟s landing records, Research vessels, and on-project fieldwork. Trends in historical landings (1985-2010) of prawns from the Malindi-Ungwana Bay were analysed using LOWESS while future landings trends are forecast using an ARIMA model. Community trend indicators based on size-spectra analyses (e.g. of number, biomass and diversity) were used to assess the ecological state of the bay. Biomass Trophic Level spectra (BTLS) and K-dominance analysis were applied as potential tools for analyzing multi-factor effects on the bay. Indiseas-based ecosystem indicators were used to quantify the impact of prawn fishery on the biodiversity of the bay. Results indicate a long-term series with two peaks (in 1997 and 2000) in historical landings of penaeid shrimps with a monotonous decline in catches from 2002. Forecasts predict a steady decline in catches for the next decade (2010-2020) under the current management strategies. Number, biomass and diversity-size spectra analysis made from artisanal landings (2008-2012) indicated effects of fishing on the ecosystem. The number and biomass-size spectra analysis showed increased fishing mortality with time (2008-2012) and an apparent increase in fisheries productivity of the bay. BTLS analysis using the fish by-catch data indicated reduced levels of biomass across trophic levels and a decline in trophic levels of the fish species caught indicating a fishing-down-the food web effects. Biodiversity and conservation based indicators adopted from the Indiseas program (www.Indiseas.org) showed the Malindi-Ungwana Bay ecosystem to be ecologically degraded in terms of fish sizes, trophic characteristics and proportion of predators. The study recommended adoption of the studied ecological indicators and tools as means of evaluating and monitoring the Malindi-Ungwana Bay resources and ecosystem status. However, there will be need to initiate more long-term monitoring programs in order to strengthen the temporal scale of analysis and application of the results. In addition to the indicators described in this study, additional socio-economic and biological data will be needed to develop a holistic EAFM model for the management of the bay resources.