Long-term Trends in Coral Reef Fish Yields and Exploitation Rates of Commercial Species from Coastal Kenya

Abstract

Keywords: coral reef fish, yield, long term trends, commercial fishing, Kenya Analysis of long-term (1978–2001) marine fisheries data showed that Kenyan coralreefs produced an estimated 2–4 metric t/km2/year of demersal fish. A rapid overall decline in landings occurred during the 1990s. Yields (t/km2/year) showed bimodal peaks in 1982 (2.98) and 1991 (2.90). The average total landings dropped by 55% during the last decade following peak landings in 1982. Landings of the commercially important families (e.g., Siganidae, Lethrinidae, Lutjanidae and Serranidae) declined by about 40% during the last decade, with the groupers (Serranidae) showing the steepest (72%) decline. Analysis of landings per administrative district showed a 78% decline in the densely populated Mombasa district between the periods 1983–1991 and 1992–2001. The less populated districts have registered stable (e.g., Kilifi) to increasing (e.g., Kwale) catches over time. An autoregressive moving average (ARIMA) model forecast of landings predicted a gradual decline in catches during the next decade (2002– 2011) with a trend slope of -0.01 t/km2. Length-frequency analysis for the commercially important species indicated above optimum exploitation (E) and fishing mortality (per year) rates for the sky emperor, Lethrinus mahsena (E = 0.64; F = 2.48) and lower but strong rates for the emperor, L. sangueinus (E=0.51; F=0.93). The more abundant and commercially important whitespotted rabbitfish, Siganus sutor, showed equally strong rates (E= 0.56; F = 1.44/year). A precautionary approach in the management of Kenya\'s coral-reef fisheries is recommended. Western Indian Ocean Journal of Marine Sciences Vol.2(2) 2003: 105-116