Trends in an Indonesian coastal fishery based on catch and effort statistics and implications for the perception of the state of the stocks by fisheries officials

Abstract

Indonesia's capture fisheries are monitored in each district of all 27 provinces with a comprehensive catch and effort data recording system that was installed in 1976. The annual data are sent to the Indonesian Directorate General of Fisheries (DGF) in Jakarta, where these are aggregated for nine regions. Catches for the 45 recognised fish categories are accumulated in four major fish groups and analysed with conventional fisheries surplus models to estimate maximum sustainable yields (MSYs). These estimates have been used by DGF to determine the number of fishing licenses for each region in the nation's economic exclusive zone (EEZ). This paper discusses the effect of data aggregation and accumulation on the variance around trends in fisheries data of the South Sulawesi province. Simple regression techniques are applied to time series of catch, effort, catch-per-unit-effort, and numbers of boats. At the lowest level of data aggregation and accumulation we find the highest variance. Although high variance obscures the perception on the state of fish stocks at the lowest levels, perceptions at the highest levels are not necessarily more useful for fisheries management. Bias caused by motorisation of the fleet by using CpUE as an indicator of fisheries mortality and by combining data from administrative units that have no ecological or biological meaning obscures the detection of trends.