2. BACKGROUND INFORMATION

2.1 Prior Reports

2.1.1 United Nations feasibility survey for the hydraulic control of the Laguna de Bay complex and related development activities

This report (UN, 1970) is currently under review by the Executing Agency, the United Nations Office of Technical Co-operation, but has been furnished to the LLDA on an advance basis, so that programme formulation could proceed. The report presents a series of studies, all generally oriented to development of the Laguna de Bay region. The scope of the report is evidenced by the following summary of the contents.

The matters of major interest in the report for fishery development are the Water Quality studies, Volume 3, Part II; the proposals to utilize the lake waters extensively for water supply for Manila and suburbs, Volume 4, Part II; for Irrigation, Volume 4, Part III; and Volume 5 on Fishing. Volume 5 shows that the fish catch on the lake is quite high, amounting to 40 000 t annually over 90 000 ha, but that the fish catch returns are marginal because of poor quality fish of low market value. Three development proposals are made. These are:

1. development of a balanced lake fishery through improved species and better management to yield 2 t/ha;

2. construction of a 152 ha project knows as Lumban Fish Pond at an estimated capital cost of 3.3 million;

3. construction of a 3 720 ha fish pond reclamation complex in the East Bay at an estimated capital cost of 75.5 million.

The report proposes two types of intensive fishery production in the proposed fish pond projects. These production methods involve “standard accelerated pond” and “multiple sequence” procedures which are considered to have potentials for increasing present fish pond production in the Philippines from between 500 and 1 000 kg/ha to more than 4 t/ha. These fish pond procedures are indicated to provide continuity of fish pond production for harvesting on a day to day basis rather than the seasonal basis of present fish pond production in the Philippines.

2.1.2 FAO/UN, 1961; FAO/UN, 1962; Rabanal, Acosta and Delmendo, 1968, reports

The FAO/UN (1961) report deals with operation and organization of the Limnology Project, 1959–1960. It is an account of the limnological programme developed for Laguna Lake, wherein studies on fish population, fisheries census, snail studies, plankton and physico-chemical investigations were outlined. This work was the basis of the technical programme followed by J.W. Parsons in 1962.

Parsons (FAO/UN, 1962) gives some basic information obtained on limnological studies carried out in Laguna de Bay during his tour of duty. The existing species were reported. Specific recommendations were presented concerning lake fisheries management and the course of action to be taken by the Philippine Government to develop the fisheries of the lake.

The Rabanal, Acosta and Delmendo (1968) report gives information on the aquatic productivity of the lake.

2.1.3 Shimura and Delmendo

This report (Shimura and Delmendo, 1969) submitted to the Fisheries Commission, deals with a fishery survey of Laguna de Bay covering a period from September to November 1968. It was an initial attempt to develop a statistical system on fish catch and related activities covering inland waters for the Philippine Fisheries Commission.

The survey consisted of two stages. First, a survey was made of the number of fishing families, number of fishing gear and number of duck farms. The second stage was a survey of duck feeds and fish catches obtained from the lake.

The report stated that in 1968 the lake produced an estimated average of 0.4 t/ha/year of fish, more than 1.0 t/ha of snails and 0.3 t of shrimps. Compared with an earlier report by Delmendo (1966) there was a decrease of more than 50 percent in fish catch and about 60 percent in snails. On the other hand, shrimps increased by about 45 percent. The difference in figures in the two reports is probably due to improvement in the statistical design and methods of sampling. The 1968 survey was based on interviews of fishermen around the lake, while the 1966 report was based on catch sampling carried out from 1961 to 1963. No recent data are available on the present fish catches from the lake except those given in the above reports.

2.1.4 Laguna Lake Development Authority objectives and priority programme (dated 15 March 1971)

This document, prepared by the General Manager of the LLDA, has been adopted by the Board of the LLDA as its overall current programme and is included in this report as Appendix 1. The programme incorporates various recommendations of the United Nations report into Phase One and Phase Two developments. The two phases are intended to proceed more or less simultaneously, with emphasis on all aspects of Phase One and selected parts of Phase Two.

Phase One includes the following: design and construct a hydraulic control structure with navigation lock; study and design a comprehensive water quality and management system for the whole lake; study and design irrigation systems with ground and surface water sources, and design and install the water treatment plant. Two other major activities, establishment of an industrial estate and agribusiness projects, are also included under this phase.

Phase Two includes infrastructure, agribusiness, industrial and other developments. Fishery development is considered relevant to both phases and is treated as an element of agribusiness development. The fishery programme of the Authority is presented in very abbreviated form in the basic programme document and the following elaboration is based on an unpublished paper by Mrs. M.N. Delmendo, which has been utilized by the Authority as its main guideline. The elements of a fishery programme from that paper are as follows:

1. Establishment of a Laguna Lake Fishery Investigations and Aquaculture Station with facilities for fish hatchery work. Experimental work would be undertaken in the following fields:

   1. Aquaculture in a land-based fishery or fish pond production. The experiments would determine both management requirements for multispecies cultivation of fish, usage of fish feeds and fertilizers, optimum total crop production and economics and other management aspects of fish pond production.

   2. Aquaculture in natural waters. Fish corrals and pens such as the 40 ha pilot project at Looc now in operation would be utilized to demonstrate the technique of this type of aquaculture in the lake. Floating net cage fish culture as practised in Japan would be tried on an experimental basis.

2. Introduction of species and production of fish stock. Various species of carp, Tilapia nilotica, and freshwater catfish would be imported and bred for aquaculture experiments.

3. Organization and establishment of fishery cooperatives. Studies would be undertaken on methodology and potentials for organization of the 10 000 fishermen on the lake into cooperative units to promote improved fishery production on the lake.

Overall, the foregoing programmes have been planned in some detail to encompass a proposed five-year fishery development programme.

2.2 Laguna de Bay

2.2.1 Physical characteristics

Laguna de Bay has an average depth of 2.8 m and a surface area of 90 000 ha. Dissolved oxygen is in order of 5 to 9 ppm and is generated by photosynthesis of the lake algae. The annual fluctuation in stage between the dry season and the wet season is between 2 and 3 m. Chlorides generated by inflow from Manila Bay during the dry season result in concentrations of between 100 and about 1 000 ppm between the dry and wet seasons of the year. However, during periods of extreme drought, as in 1969 and 1970, chloride concentrations rose to levels of 2 000 to 4 000 ppm. The lake turbidity varies from 25 to more than 500 ppm, depending upon the occurrence of storms, which may cause extended periods of turbidity over a considerable period of time. The United Nations studies indicate that sedimentation is not a serious problem in the lake and that only in the East Bay is some slight shallowing occuring, primarily because of estuary formation by large tributary streams, i.e. the Santa Cruz and Pagsanhan Rivers. Temperatures are at the ambient level of 28° to 30°C, corresponding to atmospheric conditions. Except for one limited area of weed growth in East Bay, there is no known stratification in temperature, chloride concentration or oxygen within the lake because of the continual mixing caused by wave action. The major physical change expected in the lake when the hydraulic control structure proposed in the report is constructed is a reduction in total dissolved solids which are about 1 500 ppm and a reduction of chloride to 25 ppm or less. Moderately high pH values occur throughout the lake and are generally in the order of magnitude of 8.6 to 8.8. Detailed information on nitrogen and phosphate content, on plankton count and algae characteristics are available from the United Nations report.

2.2.2 Ecology

Temperature, pH and dissolved oxygen are in an ideal range for warm water fish culture. The lake is rich in natural food, which consists of plankton, benthos and higher aquatic plants. There has been no direct determination of primary production. However, the existing high yield of the lake fishery is one of the highest reported in natural bodies of water. No determination of the higher aquatic plants has been made but this is estimated to be quite considerable, particularly in the East Bay area and along the shallow margins of the lake.

Benthic fauna is composed mainly of snails, midges and annelids. The population of snails, based on Ekman dredge samples, averages 2 400 m², 500 midges and 100 annelids m² of lake bottom.

Full details of the lake's characteristics are given by Parsons (FAO/UN, 1962), Appendixes II and III, and in the United Nations (1970) Report. The present production of about 0.4 t/ha of fish and 1.4 t/ha of duck feed (shrimps and snails) indicate a high productivity of the water. The native species of the lake, primarily the gobies (Glossogobius giurus) and the perch (Therapon plumbeus) do not nearly utilize all sources of natural food. There seems to be a lack of herbivorous species. The common carp (Cyprinus carpio) and Tilapia mossambica which have been introduced to the lake are only found in small numbers, probably due to the predation of the goby. It is estimated that, by using species combinations which can fully utilize natural food from all ecological niches, the yield of fish per ha could be increased from 0.4 to 2 t/ha or more.

2.2.3 Existing species

There are 23 species found in Laguna de Bay (Delmendo and Bustillo, 1968) belonging to 16 families and 19 genera. The most common and dominant species are the gobies and perch, which have relatively low market value; and isolated catches of common carps, kanduli (Arius spp.), snakehead (Ophicephalus striatus) and T. mossambica occur in small quantities. Small freshwater snails are abundant and these are harvested to sustain the duck raising industry around the lake.

Before the present pollution of the Pasig River, migratory species from the sea were grey mullet (Mugil sp.), milkfish (Chanos chanos) and Manila catfish (Arius manilensis). The milkfish is the only species for which fry and fingerlings can now be obtained regularly from outside sources. The other two species are very highly priced but their fingerlings are not available for fish farming purposes.

2.3 Existing Laguna de Bay Fishery Developments

Studies of Laguna Lake have shown the high productivity of this body of water and also the poor quality of the dominant native species. The fish catches of fishermen are composed mainly of very small fishes and shrimps. Very limited fish culture activities, commercial or experimental, exist on the lake shore areas. Commercial rearing or production of fish through various methods, i.e. pens, corrals, cages and ponds, does not exist in the lake area. There are Government demonstration stations of limited capability, around the lake, which are used for fry and fingerling production of common carp and T. mossambica. It is evident that the introduced T. mosambica has not been established in the lake. This may be explained by the high abundance of predatory fish in the lake, mostly goby and snakehead.

2.3.1 Looc fish corral

A pilot fish enclosure at Looc Cove, Cardona Municipality, Rizal Province, made of a bamboo structure and woven bamboo screen of 40 ha and stocked with 120 000 milkfish on 20 March 1971, is at present in operation as a rearing pen. This project was constructed and operated by the LLDA to study the feasibility of lake aquaculture. It is intended to provide the lake fishermen with alternative methods of producing fish, if found practical. The fish harvest began 9 July 1971 utilizing gillnets and, as of this report, was not yet complete. Six tons (16 000 fish) have so far been harvested but it is hoped that at least 50 percent of the original number stocked can be recovered. The initial harvest was slowed down by lack of equipment, which has been recently remedied. The harvest fish have been almost entirely grown on natural foods. Their body condition is excellent and better in comparison with some fish reared in tidal ponds. The reason that only milkfish fingerlings were stocked in this demonstration area is that no fingerlings of other species were available at the time of stocking. The unsuitability of the dominant native species found in the lake is suggested in the Parsons report.

2.3.2 Fish culture stations

Two hatcheries, one at Tanay and the other at Bay (Fig. 2) are operated by the Fisheries Commission. Fingerlings of various species are being produced for free distribution to farmers and for stocking of natural bodies of water. The rate of production from these stations is not enough to support the great demand for fish seedlings. Based on observations made at these stations, it would be necessary for the LLDA to establish and administer its own fish hatchery, possibly utilizing one of the existing stations if suitable improvements are made. Negotiations are now under way for this arrangement with the Fisheries Commission.

2.3.3 Lake fishery

Except for a few operators, the lake fisheries are mainly exploited by traditional fishing methods typical of small village fishery operations. The fishing craft are small wooden dugouts or narrow beam boats with outriggers powered by inboard motors. The lake is heavily fished, as evidenced by the existence of more than 10 000 fishermen operating on the lake.

2.3.4 Fish ponds

There are two privately-owned projects, one in Los Baños and another at Lumban, Laguna, which are at present not in active operation.

2.3.5 Fish pens in Sampaloc Lake at San Pablo

Sampaloc Lake is one of the crater lakes located in San Pablo city, Laguna Province. This body of water is deep and has a very narrow shore area. With technical assistance from the Fisheries Commission, the fishermen have innovated fish pens along the shore line, where they stock fingerlings of Tilapia mossambica collected from the lake or provided by the Fisheries Commission.

Small pens of about 60 m² for rearing fish (T. mossambica) are used all along the lake shore. These pens cost about 300 each. No data about their production or returns has yet been collected, however, the fact that they have been in continuous operation by private operators for more than three years, and that the right to use a single fish pen area is said to cost 500, indicate their profitability. This method of fish culture could be developed in Laguna Lake, provided that an adequate supply of fingerlings is available.

2.4 Other Freshwater Fishery Developments visited in the Philippines

2.4.1 Candaba

This is a locality in Pampanga Province in Central Luzon where extensive freshwater fish ponds have been developed - particularly lowland fish ponds. These are actually flood lands which were delineated with high dikes to retain water when the floods recede. The Philippine Government is giving this area technical and financial assistance to cultivate the Chinese carps in combination with the local species. The fish ponds are operated on a half yearly basis with melon or rice production in the dry season. A fish hatchery and nursery project for Chinese carp fingerling production is also located here. Fish pond yields in this area are reported to range from 0.6 to 0.7 t/ha.

2.4.2 Tarlac

A 150 ha freshwater fish pond of private ownership, constructed last year, was visited in this province. The unit cost of construction was 5 000 per ha. The cropping yield is 0.4 t ha. This low rate of production is probably due to its very new construction, which caused the low soil fertility, and use of only common carps as the only species available for stocking.

In this site, an improvised fish hatchery was utilized for induced spawning of four grass carp. This is probably the first time that the grass carp have been spawned since introduction into the country four years ago.

2.4.3 Iloilo

Information was obtained about an 8 ha freshwater fish pond about 20 km out of Iloilo city in Iloilo Province on Panay Island. The ponds are operated on a year round basis and are supplied mainly with spring water during the dry months. The project has a fish hatchery developed by the owner for the spawning of Chinese carps. It is in this project where the first successful spawning of silver carp and bighead carp took place in 1969. It has not yet produced commercial quantities of fingerlings, due to some technical problems of the operator.

The fish pond here produces about 2 to 3 t/ha/year, somewhat higher than those obtained in central Luzon ponds, probably due to the use of fertilizers and supplemental feeds.