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Bacolod City, PhilippinesMonday, March 12, 2012

PH marine biological
resources declining

Philippine marine bio-resources are declining. Marine catches by municipal fishers in the Philippines have declined since the 1980s, according to BFAR. The evidence for this decline is quite clear.

In this column today, I cite specific examples to show the declining trends as documented in several reports and published papers. Because of space limitations, no specific sources are included, but the interested reader can access publications of the Bureau of Fisheries and the academic institutions conducting research on marine resources. It is hoped that our readers will seriously consider the scientific and social implications of the declining status of our marine resources.

For this presentation, I have used three indicators to show the declining trends over periods of time: standing stock (biomass in tons per square kilometer), catch rates (catch per unit effort or CPUE), and number of individuals per unit area.

Demersal fisheries. The standing stock or biomass of bottom-dwelling fishes in Manila Bay decreased from 4.61 tons/square kilometer in 1947 to 0.47 tons/square kilometer in 1992. The CPUE of demersal fisheries in the country was 16.2 kilograms/hour in 1957 as measured by standard trawls; it is only 8.8 kg/hr today.

Coral reef fisheries biomass in the 1930s and 1940s has been estimated to average 100-120 tons/square kilometer, sometimes reaching 200 tons/sq km; in the 2000s it is only 5-20 tons/square kilometer. Because of this low biomass or standing stock, the yield or CPUE of hook and line fishers has been found to be low, 0.5 kg/fisher/hour (fishers fish for three to four hours per day). This CPUE can be increased by establishing marine reserves.

Other estimates of CPUE of hook and line reef fishers are greater than 10 kg/day in the 1950s, greater than 5 kg/day in the 1970s, and less than 5 kg/day in the 1990s.

Pelagic fisheries. Pelagic fisheries include species that move far and wide such as tunas and mackerels. The hook and line CPUE for pelagic fisheries has been estimated at 2-3 kg/fisher/day now, compared to the CPUE in the 1930s, which is estimated to be at least 20 times larger. This estimate seems reasonable; I recall this large catch when I accompanied a fisher-friend to fish in the Sulu Sea in the late 1930s.

Tuna landings in southern Mindanao have been reported to have declined. BFAR records show that 352,000 tons of tuna were landed in 2001. This has declined to less than 200,000 today, and Filipino fishers have to range far out to areas beyond Philippine marine waters to catch tuna.

Giant clams. From tens to hundreds of individuals per hectare in the past, giant clams exist in fewer numbers today. Two species are now locally extinct.

Shrimps (Penaeus). Catch rate in 1977 was about 8.5 kg/hour; catch rate is now 0.89 kg/hr in the Visayan Sea.

Irrawaddy dolphin. This species has been reduced to about 77 individuals in 2000s and could become extinct if mortality is not reduced.

Dugong. This species has been reduced to few individuals in Palawan and Davao Gulf and is considered endangered.

Sea turtles. These species were common in the Turtle Islands in the 1930s and laid three million eggs. Now only about 1/10 of this number is laid. To maintain a stable population, about 70 percent of the three million eggs need to hatch successfully.*

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