5.1. Land And Water Use
5.2. Environmental Impacts
Land and water use in the Philippines is governed by existing laws and shall be discussed in a later section. As was mentioned earlier most fishponds in the Philippines are brackishwater ponds that were developed out of mangrove swamps. Land can be considered a premium commodity in the Philippines. Thus it is rare to excavate a good agricultural land to convert them into fishponds since this would make lower the market value of such land as a real estate.
It was only during the mid-1980s when many such conversions took place particularly in the province of Negros Occidental in Central Philippines. At that time sugarcane plantations were converted to brackishwater ponds for intensive shrimp culture. It was a time when the world market price of sugar was depressed while the shrimp market was soaring. It is not clear whether or not an environmental impact statement was required for such conversion as is required when mangroves are involved. Such conversion normally requires prior clearance of the Department of Agrarian Reform instead. This is to ensure that the conversion is not done merely for the purpose of being exempted from land distribution under the Agrarian Reform Law.
Foreshore areas, lakes, rivers and other bodies of water are part of the public domain and cannot be claimed or titled by anybody. The use of portions of a lake, river or sea for aquaculture and other purpose requires a prior permit from the local government. The use of mangroves which are considered part of forest-lands is regulated by the national government. Freshwater resource whether from surface or ground sources also comes under the jurisdiction of the national government. A creek passing through a private property may be used exclusively by the owner of the land through which it passes, only with an appropriate license from the National Water Resources Board.
5.2.1. Brackishwater Aquaculture
Most, if not all of the brackishwater aquaculture ponds in the Philippines were developed on mangrove swamps. It is estimated that of some 400,000 ha of mangrove forests, less than half remains untouched. Most have been developed into fishponds which later may also have been converted into shrimp ponds. The approach of most fishpond developers have been to clear-cut an area even up to the water edge in total disregard of existing regulations requiring at least 50 meters of mangrove to remain uncut. The mangrove forests which is the interface between the land and the sea is now recognized as a rich nursery ground for various marine species.
When the technology for intensive shrimp farming became available, additional stress on the environment was introduced in the form of chemicals and antibiotics used for pond preparation, pest control, prophylaxis and shrimp disease management. Then when it became evident that inter-tidal mangrove area is not really the best place to practice intensive shrimp farming after all, many good agricultural lands were also converted into shrimp ponds with the effect of actually salinizing a perfectly good agricultural land. This happened on a large scale in the province of Negros Occidental where large tracts of sugar cane plantations were converted into shrimp farms.
5.2.2. Freshwater Fishponds
Freshwater fishpond operation as practiced in the Philippines is not known to have had any adverse environmental impact. Extensive and semi-intensive operation seems to be the rule. Even if intensive culture is practiced, the wastewater should not pose any problem if this is used to irrigate croplands instead of being discharged directly to a body of water. One such intensive operation which produces more than 100 mt of tilapia in a 1.44 hectare area does just that by using the wastewater to irrigate the surrounding sugarcane plantation.
5.2.3. Fishpens
Fish containment structures in a body of water potentially pose more negative effects to the environment. Beveridge (1984) enumerated three principal ways for cage and pen structures to affect a water body:
The fishpen development in Laguna de Bay can be considered a classic case in competition for space. Competition actually occurred in two levels: one between the rich fishpen operators and the impoverished lake fishers, the other between the cultivated species (milkfish) and the natural lake biota.
The uncontrolled proliferation of the fishpens deprived the small fishers of their freedom to navigate and fish freely anywhere in the lake. This was a very acute social issue in the early 1980s when the fishpens occupied 35,000 ha of the lake’s 90,000 ha area. The total fishpen area slowly dropped over the years to reach only 5,700 ha in 1989 (Zafarella, 1994). It has not grown since and may even be still dwindling. At present the registered fishpens occupy a total area of 4,425 ha based on fishpen licensing records of LLDA. Illegal fishpens still exist but are all reportedly small and probably comes up to a total of a few hundred hectares.
The competition between milkfish, the farmed species, and the rest of the lake fishes is evident when the total fish production from the lake before and after introduction of the fishpens are compared. Delmendo and Gedney (1974) found that the open water fish catch declined markedly from 433 kg/ha in 1968 to only 246 kg/ha in 1973 when fishpens were already introduced as shown in Table 25. In terms of fish catch volume, the decline was somewhat offset by the 3,999 kg per ha from the fishpens. Average unit fish production from the entire lake inclusive of the fishpen went up to 444 kg as against 434 kg per ha although total catch including crustaceans and mollusks dropped from 1,812 kg to 1,657 kg per ha.
It is in the value of the fish caught that the fishpen made a positive impact. From only PHP651 the value went up to PHP1,446 per ha. The milkfish has a much higher value than the existing fish species in the lake. The 19,204 mt of milkfish from the fishpen was worth PHP76.8 million while the 20,723 mt of miscellaneous fish from the open water was worth only PHP53.3 million. The unfortunate fact however is that while fish from the open water is free for anyone to catch, the fish in the fishpen benefited only a fortunate few.
5.2.4. Fish Cages
Unlike fishpens, fish cages are set above the bed of the body of water where they are set. Conceivably bottom fish and shellfish are free to forage under such structures. No “before and after” fisheries data has been collected for a body of water where fish cages has been introduced. However the effect of uncontrolled proliferation of fish cages in a small lake on the dissolved oxygen regime and growth of the fish in the cages in Sampaloc Lake is well documented by Santiago and Arcilla (1993).
Sampaloc Lake is one of the seven crater lakes in San Pablo City, Southern Luzon. Almost circular, the lake has a surface area of 104 ha, 3.5 km perimeter and an average depth of 20 m. After its initial introduction in 1976, the number of tilapia cages grew to occupy an area of 6 ha by 1980, as an increasing number of small lake fishers turned to fish farming. As shown in Table 26, the fish cage area doubled almost every 3 years, eventually reaching 28 ha by 1987, or 26.9% of total lake surface, even if fish growth already slowed down by the time the cage area reached 10 ha in 1982. The industry continued to grow at a slower rate until it occupied 28 ha in 1989.
In 1980 to 1981, when there were only 6 ha of cages, the average daily increment (ADI) was 1.09 to 1.12 g per day. Harvest size ranged from 200 to 250 g after 180 to 240 days in 1980; and from 167 to 200 g after 150 to 180 days in 1981. By 1982 and thereafter the ADI ranged only from 0.35 to 0.42 g per day. Harvest size ranged from 143 to 167 g after 360 to 540 days. In 1986, the fish cage operators started giving commercial feeds. This apparently enabled the fishfarmers to obtain 200 g size fish in 120 days. It is estimated that a 10 x 20 x 5 m cage (the most common size) which is typically stocked with 3,150 pieces of tilapia, consumes 1.25 mt of commercial feeds per cropping cycle. Extrapolated per hectare this is equivalent to 62.5 tons. With three croppings a year it is estimated that the lake would have received 5,250 mt of feeds from the 28 ha of cages.
Santiago and Arcilla (1993) found the dissolved oxygen in Sampaloc Lake to drop substantially below 2 m. With a DO from the surface to 1 m depth ranging from 5 to 12 mg/l, saturation level ranged from 50% to more than 100%. At 2 to 3 m, DO rarely exceeded 4 mg/l. Saturation level at 2 m occasionally reached 50%, and only 10 to 40% at 3 m. This was blamed on the weak circulation and the decomposition of organic wastes. The oxygen loss was most severe at 5 m. In 1989 DO levels were 4 mg/l equivalent to 49% saturation. In 1990 and 1991 DO level fluctuated only between 0.2 to 2.0 mg/l with saturation equivalent to <30%. The disappearance of oxygen at 3 m gave the waters at 5 m the characteristics of a hypolimnial layer which normally occurs in deeper waters. Thus even a minor agitation causing partial overturn can result in massive fish mortality as has happened several times.
The sea cages have not been introduced long enough for any adverse environmental impact to be noticed. However based upon the experiences of other countries such as with long experience in their use, such as Japan and Norway, it is known that indiscriminate installation and operation can also have serious environmental consequences in such as accumulation of organic matter on the seabed which later would undergo anaerobic decomposition.
5.2.5. Oyster and Mussel Farms
Oyster and mussel farms have been around for several decades in various parts of the Philippines. At most they take up space and impede the free flow of water, but unlike fishpens and fish cages, mussel and oyster farms do not totally exclude small-scale fishing activities. They merely limit the type of fishing gear that can be used. Although no study has been made on the build-up of silt within oyster and mussel farms, the experience of Binakayan in Cavite and Dagat-dagatan in Malabon show that long term use of an area for oyster farming makes the area progressively shallow.
They do require external inputs. For oysters these consist of bamboo poles used for stakes, nylon monofilament fishing lines for stringing up empty oyster shells used as spat collector and attachment surfaces. For mussels these would be bamboo poles and perhaps polypropylene ropes and buoys if suspended culture methods are used. But such materials are brought in at most only once during each growing cycle and in some cases are even reusable. Furthermore these materials either react slowly with, or are practically inert to, seawater. They can also be physically removed. Thus far there has been no public complaints raised against such farms.
5.2.6. Seaweed Farms
Like mussel and oyster farms Eucheuma farms also take up space but are mostly submerged. What are highly visible are the drying platforms and the caretakers’ huts. But such structures are often made of light, locally available materials such as bamboo and nipa palm leaf thatching and seem to blend in with the scenery. Again the exogenous inputs are similar to oyster and mussel farms: bamboo or mangrove poles, nylon monofilament lines or polypropylene rope. Polypropylene twine often referred to as “straw” is also used extensively for tying the cuttings or seedstock to the growing lines. The mangrove poles are small, normally branches from Rizophora trees and can be obtained without cutting whole trees. Seaweed farms do not exude effluents. Instead they act as nutrient sinks.
