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SummaryCharacteristics, impacts and economic costs and benefits of blast fishing have been little investigated and they were therefore studied in Indonesia, at the scale of individual fishing households and of Indonesian society as a whole. Although illegal and highly destructive to coral reefs, blast fishing provides income and fish to a vast number of coastal fishers who claim that they have no alternative to make a living. Crew members in small-, medium-and large-scale blast fishing operations earned net incomes per month of US$55, 146 and 197 respectively. Boat owners in the same types of operations earned US$55, 393 and 1100 respectively. These incomes were comparable to the highest incomes in the conventional coastal fisheries. At the individual household level, the differences between the three types of operations show clear incentives for scale enlargement. The cost-benefit balance at the society level was calculated with an economic model. This analysis showed a net loss after 20 years of blast fishing of US$306 800 per km 2 of coral reef where there is a high potential value of tourism and coastal protection, and US$33 900 per km 2 of coral reef where there is a low potential value. The main quantifiable costs are through loss of the coastal protection function, foregone benefits of tourism, and foregone benefits of non-destructive fisheries. The economic costs to society are four times higher than the total net private benefits from blast fishing in areas with high potential value of tourism and coastal protection. This analysis of characteristics, impact and economics of blast fishing should help to raise the political will to ban blast fishing from Indonesian waters. Moreover, it allows for an evaluation of possible management solutions, taking into account their costs and the socio-economic framework that caused coastal fishers to start using explosives.Keywords: Indonesia, coral reefs, blast fishing, coastal management, socio-economics IntroductionBlast fishing was introduced in the Indonesian Archipelago in the Second World War as an easy and profitable way to catch schooling reef fish (Galvez et al. 1989). Nowadays, due to generally declining catches in other sectors of coastal fisheries (Venema 1997), the ranks of blast fishers are joined by fishers who consider blast fishing the last opportunity to catch and earn enough to feed their families. The explosives were originally taken from old Second World War ammunition shells, which were dug up by fishers. At the present, bombs are mostly made with artificial (chemical) fertilizers such as ammonium and potassium nitrate (NH 4 NO 3 ; KNO 3 ). Sometimes, dynamite obtained from police, military personnel, mining companies, or civil engineering projects is also used (Alcala & Gomez 1987;Rubec 1988;Galvez et al. 1989).Blast fishers hunt specifically for schooling reef fish, so that only a few bombs will assure a relatively large catch. Because they can use visual information on the abundance of their prey, they consider this method to be very cost-eff...

SynopsisWe identify fishery management implications from a long-term monitoring program focusing on spawning aggregations of high valued reef fish in Komodo National Park (KNP), Eastern Indonesia. Management objectives of KNP are not only to protect biodiversity, but also to conserve spawning stocks of high-valued commercial species for the replenishment of surrounding fishing grounds. We monitored two sites twice monthly over five years for two species of grouper, Epinephelus fuscoguttatus and Plectropomus areolatus. One site had an aggregation of both E. fuscoguttatus and P. areolatus, whereas the other site contained an aggregation of P. areolatus only. Over the five years monitoring period, aggregations typically formed during each full moon between September and February. Additionally, P. areolatus occasionally aggregated during new moons between April and July. We observed spawning only once, but because formation of aggregations were correlated to a higher incidence of behavior and signs indicative of reproduction and because most fish present were adults, it is likely that the formation of aggregations was associated with spawning. Over the five years monitoring period there was a reduction in mean fish size of up to 8 cm for P. areolatus, and a reduction in numbers of aggregating E. fuscoguttatus. Despite limited protection initiated in 2001, both sites are still heavily fished by local artisanal fishers. Because the observed reductions in size and in numbers could be caused by fishing pressure, managers should follow the precautionary principle by putting additional protective management in place. Since both species are relatively long-lived, at least five years of continued monitoring may be necessary to determine the outcome of management intervention. The variability in timing of aggregation in respect to season and moon phase in P. areolatus indicates that long-term monitoring must cover the entire year and both moon phases.

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