Changes in the fish diversity and abundance on a heavily fished fringing reef on Santiago Island, Pangasinan, Philippines
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Fish assemblages on the reef slope, reef flat, and seagrass beds on Santiago Island were sampled over 18 months in 1992-1993 as part of a 6-year reef monitoring project started in 1986. Abundance and species diversity were analyzed by a variety of indices, and by multi-dimensional scaling and correlated ordered similarity matrix. The monitoring showed a distinct shift in the reef slope fish composition during the first half of 1988. Of the 100 most abundant species, 21 species showed significant reductions in abundance, and 20 species showed significant increases. Differences were not due to depth preference or feeding habits. Fishing pressure was apparently responsible for declines in Cheilinus trilobatus, Acanthurus nigricauda, and Naso literatus, as well as a general decline in the family Acanthuridae (surgeonfishes). However, analysis of site preferences of the decreasing species and the increasing species indicated a shift in community composition from those species preferring more coral cover to those preferring more sand, rock, and possibly Sargassum seaweed. Site preferences were determined from benthic life form transects done in 1992. Of 35 significantly changing species for which habitat data was obtained, 24 fit the hypothesis of habitat change. This supports the proposition from previous studies that the major cause of change in the reef slope fish community was the destructive fishing activity associated with Malthusian overfishing. Similar analyses of the fish assemblages on the reef flat and on the seagrass beds showed seasonal effects, particularly in the latter, but no strong shift comparable to that of the reef slope. These latter areas had been subjected to greater fishing pressure for a longer period. Reef fish populations such as those in Bolinao tend to be highly resilient provided the larval supply is not adversely affected. However, subtle changes in the cover of coral on a reef can lead to major changes in the composition of the fish community. Coral cover is being widely diminished on Philippine reefs, and substantial changes in the fish communities may be anticipated, even on reefs with initially low coral cover. These changes may affect the utility and immediate value of the fish to local fishers and the market systems they supply. It is of great urgency to stop destructive fishing practices such as blasting and use of cyanide, and to develop anchoring methods that are minimally destructive. There is a strong predictive relation between the numbers of fish (abundance) in an area and the numbers of species (biodiversity) they include. As fish populations decline due to destructive fishing, or highly concentrated non-destructive fishing, the local species richness may be expected to decline. This decline may have serious short-term social and economic consequences, as well as far-reaching long-term environmental effects. Efforts to reduce overfishing must be intensified—though reduction of birth rate, provision of alternative livelihoods, and curbing of destructive fishing — in order to prevent a very distressing future for the Philippine marine environment and the people it supports.
McManus, J. W., Nañola Jr., C. L., Reyes Jr., R. B., & Kesner, K. N. (2008). Changes in the fish diversity and abundance on a heavily fished fringing reef on Santiago Island, Pangasinan, Philippines. In T. U. Bagarinao (Ed.), Research Output of the Fisheries Sector Program (Vol. 2. Reports on Fisheries and Aquaculture, pp. 1-20). Quezon City, Philippines: Bureau of Agricultural Research, Department of Agriculture.
PublisherBureau of Agricultural Research, Department of Agriculture
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Total volume of 3D small patch reefs reflected in aerial photographs can predict total species richness of coral reef damselfish assemblages on a shallow back reef Because fish have a high dispersal ability, an understanding coral reef fish metacommunity structure is vital for effective conservation. Coral reefs provide patchy habitat of various sizes and scales. We examined the species–area relationship (SAR) of damselfish (Pomacentridae) assemblages over 81 environmentally homogenous patch reefs ranging 0.07–45.4 m2 with low coral cover. Patch reefs were located in the shallow back reef (<2.5 m deep) off Ishigaki Island, Japan. Reef area was measured by performing image analysis of enlarged sections of a high-resolution (>1/2500) color aerial photograph used as a fine-scale seascape map. To assess the effects of three-dimensional meso-scale rugosity on species richness, we assumed that all reefs had a cylindrical shape and examined species by volume (area × height) relationships (SVR). Patch reef volume was a better determinant of species richness than area, and the regression functions of SVR provided better estimates of patch reef species richness. Neither the observed SVRs nor SARs, however, could be explained by a random placement model alone. Our results suggest that several small reefs are likely to have higher species richness than a single large reef of equivalent area in the shallow back reef where large patch reefs are flat. Thus, total patch reef volume (area × height) better reflects meso-scale rugosity and is a useful indicator of total species richness relative to the total amount of essential habitat in shallow back reefs.
Small-scale fisheries of coral reefs and the need for community-based resource management in Malalison Island, Philippines Fish landings in Malalison Island in the west central Philippines were monitored from February 1991 to January 1992 to determine the types of fishing gear employed, the predominant species caught, the catch per unit effort (CPUE), and the yield from the coral reefs. Fishing was monitored only during the spring tide periods, after a preliminary sampling showed no significant differences among four lunar phases. A total of 494 fishing operations was recorded. CPUE (kg per fisher h−1) by gear was 1.1 for spear guns, 1.4 for spear guns with compressor, 0.4 for set gill nets, 2.4 for drive-in gill nets, 1.2 for drift gill nets, and 0.7 for hook-and-lines. The CPUEs of Malalison gears are similar to those of other coral reef fisheries. Dominant species caught were fusiliers and surgeonfishes by gill net. surgeonfishes by spear gun, and snappers and groupers by hook-and-line. The fish yield from the Malalison coral reefs was estimated to be 5.8 t km−2 year−1, which is low, and similar to overexploited. reefs in the Philippines and elsewhere. Live coral cover averages 35% in Malalison. Reef degradation, high fishing effort, low yields, and the poverty of the fishing community suggest ‘Malthusian over-fishing’. Community based management and resource enhancement are being initiated by the SEAF-DEC Aquaculture Department to protect and sustain the fishery and improve the economy in Malalison Island.
ArticleCL Marte & YP Tirol -
UPV Journal of Natural Sciences, 2006 - University of the Philippines in the VisayasAn assessment of the extensive fringing reefs surrounding Mararison lsland, Culasi, Antique was undertaken in 1994 to 1996 and in 1998 to provide scientific basis for management and enhancement of the island s resources as part of the Community Fisheries Resource Management project launched in 1991. The fringing reefs on the northwest side of the island are characterized by high percent coral cover (53-65%) consisting of very diverse coral species. The dominant forms are branching non-Acropora,with numerous small colonies of other coral forms. In contrast, the southeast side of the island fronting the fishing village is depau perate (4.7 -17.6% coral cover) with few small colonies of encrusting and massive corals characteristic of stressed reefs. However, highest coral cover consisting of dense stands of branching Acropora interspersed with branching non-Acropora was observed along the reef slope of Nablag station located at the western end of the island. Coral cover in the offshore reef (Guiob) was relatively fair (24%-46%). A total of 166 scleractinian corals were seen although only few species occurred frequently or provided high percent coral cover. Following the bleaching event of 1998, dramatic decreases (30%-61%) in live coral cover, particularly along the reef slopes, were observed in all stations.