Effects of Some Destructive Fishing Methods on Coral Cover and Potential Rates of Recovery JOHN W. MCMANUS* RODOLFO B. REYES, JR. International Center for Living Aquatic Resources Management MCPO Box 2631 0718 Makati, Philippines CLETO L. NAN ˜ OLA, JR. Marine Science Institute University of the Philippines Diliman, Q.C. 1101 Philippines ABSTRACT / Effects of fishing with explosives (blastfishing) and sodium cyanide and of anchor damage on live coral were investigated on a heavily exploited fringing reef in Boli- nao, Philippines from 1987 to 1990. A simple balance-sheet model indicated that approximately 1.4%/yr of the her- matypic coral cover may have been lost to blasting, 0.4%/yr to cyanide, and 0.03%/yr to coral-grabbing anchors, the po- tential coral recovery rate reduced by about one third from 3.8%/yr in the absence of disturbances to 2.4%/yr. These figures are subject to considerable uncertainty due to com- pounding of errors during computation. Reefs with patchy coral cover are more susceptible to damage from blastfish- ing because of targeting by fishers. Reefs with smaller corals may have greater resilience, because each unit of radial colony growth contributes a greater per cent increase in ar- eal cover. Blastfishing in particular may reduce resilience to natural perturbations, leading to assemblages of small, sparse corals and reduced patchiness. Destructive fishing is common in coral reef areas where population and economic pressures lead to a state of intense competitiveness among coastal villagers (Galvez and others 1989, McManus 1988, McManus and others 1988, 1992, Men ˜ez and others 1991). This situation has been termed ‘‘Malthusian overfishing’’ (Pauly and others 1989, 1990, see also Russ 1991, McManus and others 1992), and it is a problem that is growing rapidly as human populations grow in coastal developing countries. Two common forms of destruc- tive fishing involve the use of explosives (blastfishing) and poison. Blastfishing is used worldwide on coral reefs in at least 40 countries or island dependencies (UNEP/ IUCN 1988). Blastfishing and siltation are be- lieved to be the two most important causes of reef destruction in Southeast Asia (Yap and Gomez 1985). Poisoning is used to capture fish in at least 15 countries or dependencies (UNEP/ IUCN 1988). Damage due to anchors is prevalent in most countries with coral reefs and is associated with a variety of reef fishing methods. Thispaper isconcerned with attemptsto gain a perspec- tive on the nature and relative importance of blasting, poisoning with sodium cyanide, and anchor damage on the forereef slope of a fringing reef subject to Malthu- sian overfishing. There have been several models of coral growth in assemblages, most of which have been interannual, dynamic, and stochastic (e.g., Maguire and Porter 1977, Hughes 1984, Reichelt and others 1985, Done 1988). In this study, simple calculations were used to compare expected rates of damage and regrowth within a one-year time frame. It was intended to provide preliminary information on the rates of damage and recovery and to highlight areas for further research in preparation for more predictive, dynamic modeling efforts in the future. Study Site Santiago Island lies on the western tip of the Lin- gayen Gulf of Luzon, facing the South China Sea (Figure 1). The reef has been described in detail in McManus and others (1992), and some relevant aspects are summarized here. The reef includes a reef flat dominated byseagrassbedsintersected bychannelsand lagoons. A swimming survey was conducted in 1986 involving four transects at 1- to 2-km intervals bisecting the reef flat north to south and totaling over 6 km. Examination of all coral patches encountered revealed that approximately 60% of all recognizable scleractin- ian coral (excluding rubble, distinguished by the ab- sence of sharp surface features) was dead, and many patches showed obvious signs of blasting (e.g., fractured branching corals in radiating patterns). Participants in several informal surveys in 1978–1980 and examination of photographs from that era confirmed that the live coral had been highlydominant in nonsandyareas and KEY WORDS: Destructive fishing; Blastfishing; Cyanide; Coral; Coral reef; Coastal management *Author to whom correspondence should be addressed. Environmental Management Vol. 21, No. 1, pp. 69–78 r 1997 Springer-Verlag New York Inc.