Decline of demersal coastal fisheries resources in three developing Asian countries

Abstract

Worldwide, there is serious concern about the state of fisheries; yet for Asia, which accounts for half of the global fisheries production, information on the state of fisheries in order to guide management is sparse. In this paper we review the results of a regional study that examined the state of demersal fisheries resources in the coastal areas of Malaysia, the Philippines and Thailand. In each country time series of scientific trawl survey data (spanning 12–49 years, depending on the area) were used to assess changes in the total biomass of demersal species over time. All countries showed substantial declines in the total biomass. In Malaysia, the declines were greatest in the shallow depths (<50 m) where the biomass declined to 4–20% of the original estimates. In the Gulf of Thailand, by 1995 the total biomass estimates had declined to less than 8% of the 1965 estimates. In the Philippines, changes in the biomass were examined in different bays and fishing areas and the recent estimates of the biomass were 12–64% of the original estimates. These severe declines in the total biomass are thought to be due to over-fishing, compounded by environmental degradation. While over-fishing has been previously documented for selected species or fisheries in these countries, the fishery-independent data analysed here provide the first multi-country evidence of the widespread degradation of demersal coastal resources. Exploitation ratios (fishing mortality:total mortality), calculated from length frequency data, were on average >0.5, suggesting over-fishing. In Thailand a time series of exploitation ratios for 17 species showed increasing fishing pressure over time. Environmental degradation, in terms of changes in water quality and habitat modification and loss, has been documented in all countries and this is likely to be a contributing factor for the declines. The serious declines observed in these three countries are illustrative of a regional trend and highlight the urgent need for countries to reduce and manage their fishing capacity. This regional study also identified a requirement for key interventions, such as strengthening licensing systems, limiting entry to fisheries and increasing gear selectivity. It also highlighted the fact that the strategies developed must take into account the context of the developing countries and the broader socioeconomic role of fisheries.