BIOLOGICAL EFFECTS OF FISHERY MANAGEMENT MEASURES IN THE PHILIPPINES

by Inocencio A. Ronquillo and Ma. Ethel Gabral Llana Bureau of Fisheries and Aquatic Resources Metro Manila, Philippines

ABSTRACT

Some fishery management measures, which the Philippines have adopted to save "overfished" areas, and their effects on the fishery are discussed. The cases of the partial fishery closure of Malampaya Sound and the trawl ban in the Samar Sea are taken as examples. Malampaya Sound and Samar Sea are among the traditional fishing grounds which have been identified as "overfished" areas by the Bureau of Fisheries and Aquatic Resources. Afier the imposition of fishery management measures in these areas, trawl investigations were conducted to monitor changes in species composition and biomass. Results of trawl surveys conducted in Malampaya Sound by the Bureau of Fisheries and Aquatic Resources in 1977-1978 and in the Samar Sea by the University of the Philippines in the Visayas in 1979-1980 are cited to show how the fishery management measures adopted affect the fishery biolo- gica//y.

Introduction Fish is a very important source of protein in the Philippines, supplying about 60% of the protein needs of the people. Approximately 2% of the 60 million Filipinos are employed by the fishing industry and estimates by the National Economic Development Authority, as of December 1985, show that fisheries contributed 4.7% (at constant prices) or 3.8% (at current prices) to the total Gross National Product (GNP). Fisheries therefore plays a vital role in the economy of the Philippines and is an important sector of the agricultural and natural resource industries of the country. In 1985, total fish production was about 2.1 million mt with an approximate value of 31 billion pesos ( @ ) (about US$ 1.5 billion). Over the last two decades, the increase in human population has been tremendous, the number of fishermen increasing correspondingly due to poverty. Consequently, fish capture activities in the traditional fishing grounds of the country was intensified to meet the great demand for fish. This resulted in the over-exploitation of some of these areas and the depletion of the important marine fishery resources of the country. The problem of excessive fishing effort was compounded by conflicts between the small-scale fishermen and the commercial fishermen. This situation has caused great concern among fishery biologists and fishery'adminis- trators, planners and policy makers, and even conservation-oriented private citizens. There are many fishery manage- ment options from which the government could choose, but it decided to give priority to immediate problems, speci- fically conflicts concerning the plight of the small-scale fishermen. 2. Overfished traditional fishing grounds Kuaran (1971) estimated the total potential of Philippine marine waters at 1.65 million mt, excluding the yield from invertebrates other than shrimps and crabs. He pointed out that the Philippines is probably already harvesting a largest percentage of its potential yield than are the Southeast Asian countries in general. Fisheries data from 1975 to 1984, covering a period of 10 years, show that the marine fish production de- clined from 1977 until 1980 and then gradually increased from 1980 until 1984 (Figure 1). By and large, this trbd could mean that the level of maximum production is about to be reached. Fish landing surveys conducted by the Bureau of Fisheries and Aquatic Resources (BFAR) have shown that the fish catches consist mostly of small fishes (usually immature) of mixed species of which only a few are econo- mically useful. The observations and estimates thus evidently point to heavy exploitation of some traditional fishing grounds. Taking an initial step to save heavily exploited fishing areas from further depletion, the BFAR therefore issued in 1976 a list of "overfished" areas which included 14 important traditional fishing grounds of the country. These are: (1) Lingayen Gulf, Pangasinan; (2) Manila Bay; (3) Malampaya Sound, Palawan; (4) San Miguel Bay, Camarines Sur; (5) Visayan Sea; (6) Asid Gulf, Masbate; (7) off Polillo Island, Quezon Province; (8) off Pagapas Bay, Batangas; (9) off Northern Mindoro; (10) waters north of Panay Island; (1 1) Samar Sea; (12) parts of Bohol Sea; (13) Zamboanga Channel; and (14) Panguil Bay, Misainis Occidental.

3. Fishery management measures The government has been faced with several fishery problems, among them concern about conflicts between the municipal (artisanal) fishermen and the commercial fishermen. Dependent on fishing for their subsistence, the artisanal fishermen have complained about decreasing catches as a result of the operation of commercial fishing vessels (over 3 gross tons) in inshore waters, thereby increasing competition in the fishery. The operation of commercial fishing vessels (using trawl and purse seine which are very efficient gears in catching demersal and pelagic fish species, respectively) in municipal waters has allegedly caused the exploitation of the fishery resources of the major fishing grounds of the country to the detriment of the small-scale fishermen. Among the fishery management measures which the government has taken in resp0ns.e to the rising com- plaints of the small-scale fishermen, are the closure of some traditional fishing grounds and banning of commercial trawl operations in municipal waters. Even prior to these complaints and the BFAR's pinpointing of "overfished" areas, the government had already acted in the interest of conserving the country's aquatic resources by regulating fishing activities in several fishing grounds of the country. As early as 1939, for example, a closed season was declared for the conservation of sardines and herrings; trawl bans were imposed as early as 1959 in Maqueda Bay, Villareal Bay and Carigara Bay. Among the "overfished" traditional fishing grounds, Malampaya Sound and Samar Sea have been chosen as examples in this paper. Studies in these areas were undertaken to monitor possible changes in the fish stocks following the partial fishery closure and ban on trawlers. Malampaya Sound in Taytay, Palawan was declared closed to commercial fishing in 1973 by virtue of Fisheries Administrative Order (FAO) No. 11 1. The closure lasted for 5 years until 1978. Since early 1986 a closed season for another 5 years has been effective with the issuance of FA0 No. 154. This prohibits the operation in Malampaya Sound of any fishing gear, except simple handline, spear, crab hook, crab pot , cover pot, fish trap, fish pot, pole and line, gill net for fish and shrimps, fish corral and beach seine. The operation of these gears which are not included in the prohibition is, however, limited to municipal fishing boats (3 GT or less). In 1977, through Presidential Decree No. 1015, a ban on trawl operations was imposed throughout the country in areas 7 fm (12.81 m) deep or less, or 7 km from the shoreline (whichever came first). Later, there was a move to improve the standard of living in rural fishing communities and to conserve the municipal fishery resources against heavy exploitation. This caused the issuance of Letter of Instruction No. 480, banning the operation of commercial trawl and purse seine within 7 km from the shoreline in the marine areas of the provinces of Leyte, Samar and Sorsogon. The fishing grounds covered by the ban included, among others, the Samar Sea, one of the country's important traditional fishing areas, located at the western coast of Samar Island in the Eastern Visayas region. 4. Results of trawl investigations 4.1 Malampaya Sound In an attempt to assess the fisheries of Malampaya Sound, trawl surveys were carried out by the BFAR, through the Fisheries Research Division, from October 1977 to September 1978. The R/VRESEARCHER, a 419-GT research vessel owned by the BFAR, was used in conducting trawl investigations in the area as well as in the adjacent waters, i.e. Imuruan Bay and Bacuit Bay. Specific studies undertaken in these areas included aspects of stock assessment, acoustic survey of demersal fish resources and oceanography (particularly the physico-chemical study of the areas and plankton and benthos studies).

Unpublished papers pertaining to the results of the Malampaya Sound investigations include: (1) progress report on the assessment of the fisheries of Malampaya Sound; (2) technical paper on the estimation of abundance of the demersal fish stocks in Malampaya Sound and vicinity by Fisherkeller and Ordonez; and (3) technical paper on the seasonal variation and distribution of zooplankton biomass, fish eggs and fish larvae in Malampaya Sound by Estudillo, Gonzales, and Ordonez. Results of the studies, based on these unpublished papers, show that: (1) Foodfishes were predominant in the catch throughout the study period; (2) The catch consisted mostly of the following species: Leiognathus equulus, L. splendens, Nemipterus spp., Pomadasys hasta, P. argyreus, Psettodes erumei, Caranx spp., C. djedaba, Gazza minuta, species of the family Lutjanidae, Stolephorus spp., and Scomberoides lysan; (3) About.91% of the total catch were foodfish; 4% consisted of sharks and rays; 3070, invertebrates; and 2%, trash fish; (4) Using the modified German trawl (G-type B), the catch rate obtained was highest in December 1977 (1,195 kg/hr) and lowest in June 1978 (298 kg/hr). This was attributed to the concentration of trawling in almost the same area of the Sound; and (5) Fisherkeller and Ordonez estimated the standing stock density of Malampaya Sound, using the area swept technique, at 6.5 to 9.7 mt/km? They compared these values with those of other areas, including values of mean catch rate, total area and biomass, thus:

Mean Demersal Catch Stock Fish Rate Density Total Area Resources (Whr) (mt/km2) (km2) (mt) Malampaya Sound 1,073 6.5-9.7 178 1,733 Imuran Bay 329 2.0-2.8 170 476 Bacuit Bay 420 2.7-3.8 72 273 Manila Bay 134 0.8-1.2 18,000 21,600 Sunda Shelf 288 1.5 959,000 1,495 M

4.2 Samar Sea The University of the Philippines in the Visayas, through the College of Fisheries, conducted from March 1979 to June 1980 the Samar Sea trawl survey, in cooperation with the German Agency for Technical Cooperation (GTZ), Ltd. The survey included biological and oceanographic investigations on board the ALBACORE, the UPV/ CF research and training vessel. Results of the demersal fishery survey of Samar Sea are reported in Saegar (1981) and Armada et al. (1983). During the study period, some 11 cruises were undertaken in the Samar Sea, almost at regular intervals. The sampling period was divided into period I, consisting of cruise Nos. 96 to 104 (March to October 1979), and period 11, consisting of cruise Nos. 106 to 110 (February to June 1980). Thirty-three (33) fishing stations were allocated in various depth strata, except at 0.10 m; five of these stations were untrawlable. Results of the Samar Sea trawl survey show that: (1) The mean catch (cpue) was 91.8 kg/hr (geometrical mean) for period I and 191.8 kg/hr (GM) for period 11; (2) The biomass was estimated at 1.0 mt/km? for period I and 2.1 mt/km? for period 11. Citing Pauly (1980) on the estimate of 4.0 mt/km? for a virgin stock in water depths down to 70 m, it was assumed that the biomass in Samar Sea had increased from 1/4 of the virgin biomass to about one half of it; (3) During the months of March, April and May, 1979, the mean biomass for all depths was found to be 1.52 mt/km?, with a mean biomass of 1.21 mt/km? in the depth range of 10 to 59 m; (4) During the same months in 1980, the mean biomass of all depth categories combined had increased to 3.09 mt/km? For the depth range of 10 to 59 myit had increased to 2.80 mt/km? Villoso and Hermosa (1982), reporting on the demersal trawl fish resources of Samar Sea and Carigara Bay, added that: (1) During the 1979-1980 study of Samar Sea, the total catch amounted to 52.23 mt of fish and invertebrates at an average of 172 kg/hr; (2) The catch consisted of commercial fishes (8l.2%), trash fish (10%) and invertebrates (8.8%); (3) Eighty two families of fish were identified, only 11 of which were considered commercially important. These are the slipmouths (30.85%); lizard fishes (7.84'70); mojarras (5.98%); scads, crevalles and cavallas (5.48'70); nernipterids (4.72%); mackerels (4.72010); goatfishes (4.12%); bigeyes (3.21%); hairtails (2.22%); Indian anchovies (1.84%); and barracudas (1.41 %); (4) The standing stock size was estimated to be 6,178 mt with a mean density of 2.36 mt/km? in regions between 10 and 100 m.

5. Discussion The partial closure of Malampaya Sound in 1973 is an example of a fishery management measure (imposed by the government through the BFAR) which has received various criticisms, yet gained recognition from some sectors because it was effective in rehabilitating a depleted fishery, Certainly the closure has effected a socioeconomic and biological impact on the fishery. On the one hand it lessened competition and conflicts between the municipal fishermen and the commercial fishermen. On the other hand, it increased the productivity of the area and the catch rates as well as allowing more foodfishes to grow. Generally, when some species disappear in a demersal fishery due to overfishing, other species may take over to replace them. Hence, the total production of an area remains more or less the same although the catches comprise smaller fishes. The BFAR findings point out that Matampaya Sound (with a stock density of 6.5 to 9.7 mtlkm?) is very productive as compared to other fishing areas. The fishery restriction somehow contributed to this productivity by allowing the fishery to recover. Restricted fishing areas are believed to recover after some time. Normally, when these areas are opened to fishing again, a "rush" of fishing activity by fishermen from different areas of the country would develop to exploit the seekingly revived fishery resouces. This "rush" would ultimately put the fishery back to the depleted state. In view of the successful result of the 1973 closure of Malampaya Sound, the government has imposed the same fishery management measure by establishing anew (through FA0 No. 154 signed in April 1986) a 5-year closure to conimercial fishing in the area to maintain the good state of the fishery and thereby conserve the aquatic resources thereat. The good effect of the commercial trawl ban in the Samar Sea area is clearly shown by the constant increase of biomass during the 1979-1980 survey. Saeger (1981) pointed out that the biomass vaiues obtained from the Samar Sea study indicate that the complaints by the small-scale fishermen about decreased catches seemed to be justified indeed. This is especially evident if the values are compared with the biomass of virgin stocks (5.0-6.0 mt/km?) in the continental shelf region in most Southeast Asian countries which generally have a potential maximum sustainable yield (MSY) of about 3 to 5 mt/km?/yt. Results from the 1979-1980 study in Samar Sea clearly showed an increase in biomas with depth. Over the depth range of 10 to 59 m, from example, biomass increased by more than 100%. This depth range is the most seriously affected of all the depth ranges as it covers the area where both municipal and commercial trawling are concentrated. The increase of biomass in the 10 to 59 m trawling area clearly shows that the imposition of a trawling ban is, in tropical waters, a suitable tool to protect the vital interests of the sustenance fishermen by helping heavily exploited fish stocks to recover (Saeger 1981). At the time of the Samar Sea trawl survey, there were only a few commercial vessels fishing illegally in the area. This observation and the results of biomass increase indicate that a regulation of fishing effort brings about beneficial effects on the improvement of the size of the standing stock in shallow waters which are trawlable. It means that on the assumption that stock size should be kept at at least half the virgin stock size or should not be reduced below 2.0 mt/km? in the area, regulation of fishing effort is justified.

Year Figure 1. Philippine marine flsh production, 1975-1984. Source of data: Fisheries Statistics of the Philippines, 1984.

References

ARMADA, N.B., C. HAMMER, J. SAEGER and G. T. SILVESTRE, Results of the Samar Sea trawl survey. Technical reports of the Department of Marine Fisheries No. 3, edited by J. Saeger, Dept. Mar. Fish, Coll. Fish., U.P. in the Visayas, 1-45. KUARAN, E. R., Marine fisheries potential in the Philippines and Southeast Asia. Fisheries Newsletter (July-Dec.) lg71 BFAR, 8-17. PAULY, D., A selection of simple methods forthe assessment of tropical fish stocks. FA0 Fish. Circ., 729, lg80 54 pp. SAEGER, J., Do trawling bans work in trogical waters? ICLARM Newsletter 3(4): 3-4. 198 1

VILLOSO, E.P. and G. V. HERMOSA, Jr., Demersal trawl fish resources of Samar Sea and.Carigara Bay, Philippines. Reprinted from Fish. Res. J. Phil. 7(2):59-78.