2. FRESHWATER AND BRACKISHWATER POND CULTURE

2.1 Milkfish culture in brackishwater ponds

Of all the ASEAN countries, Indonesia and the Philippines have the most extensive areas devoted to brackishwater fish culture of milkfish. The area used and the unit production per ha per year is summarized in Table 1. From 1960 to 1984, the area of brackishwater ponds in Indonesia increased from 145 144 ha to 225 197 ha or an increase of 76 percent; in the Philippines, from 1940 to 1985 there was an increase of 236 percent in area. In terms of unit production, Indonesia increased the level of output from 297 kg/ha/yr to 632 or an increase of 113 percent while in the Philippines there was an increase from 350 kg to 969 kg/ha/yr or 117 percent over the last four decades.

Table 1. Increase in area and total and unit production of Philippines and Indonesian brackishwater ponds (1940–1985)¹

Source: National fisheries statistics for Indonesia and the Philippines. These ponds are mainly used for raising milkfish.

¹ Source: Rabanal, 1987.

* Data not available.

The brackishwater ponds used to be mainly for raising milkfish. However, in recent years, conversion into shrimp ponds have been made due to the breakthrough achieved in shrimp farming technology. Nevertheless, a large part of the existing brackishwater areas are still being used for milkfish farming. Future assessments on this should indicate the areas devoted to shrimps and milkfish culture.

In existing brackishwater fishpond operations in the Philippines, farming management practices vary from place to place and farm to farm. There are those who practice monoculture, polyculture or both depending on the skill and experience of the farmer. By farming management techniques, there are those that apply fertilizers, pesticides and provide supplementary feeds while others apply one or a combination of two or three inputs in the course of the fish production cycle. Cropping intensity also vary and so is farm size.

The levels of production and income per hectare by farm management practices and size of farm is summarized in Table 2. A pond size less than 2.0 ha earns a net income of 6 231/year; 5–10 ha ponds earn 5 229/year, and more than 20 ha ponds earn 3 513/year, It is evident that smaller pond size is more efficiently managed than larger ponds. For polyculture systems, pond size of 5–10 ha yields the highest per unit area. Economic performance data ranging from 2.0–10 ha. Where new ponds will be developed an economic size farm area will have to take into account current costs of development and the cost of acquisition. It is estimated that 30 000/ha would be required for brackishwater and 20 000/ha for freshwater pond development (Librero, 1985).

Recent demonstration activities conducted at the Brackishwater Aquaculture Center on semi-intensive milkfish and shrimp farming showed a net income of 6 173/ha/year (Table 3). The ratio of net income to cost of production is about 71 percent and 41 percent to gross income. Assuming that other costs such as depreciation and maintenance, interest and rent make up a total of 30 percent of the reported production costs, the ratio of net income to gross income per ha would still be 24 percent. This rate of return on investment is about the same as the survey results made on the economics of aquaculture in the Philippines a decade ago (SCS/76/WP/37, 1976).

Brackishwater fish farms are gradually being devoted to the production of high value products such as the shrimps. This is due to the increasing demand for shrimps in the international market and the technological advances attained in the production of shrimp juveniles under hatchery conditions. Interest in shrimp farming is also generated by financial assistance made available by governments through loans obtained from local and international funding institutions such as the Asian Development Bank and the World Bank.

Table 2. Yield and profitability per hectare of milkfish culture by farming practice, Philippines (1978–1979)¹

^a Totals for individual farm practices may differ because only responding farms are reported or, in some cases, several practices may be used on one farm.
^b Per hectare of rearing area.
^c Per hectare of operational area.
^d A = fertilization; 8 = pest eradication by use of chemicals; and C - supplementary feeding.
^e Should be regarded with caution as it is based on a sample of only one farm.

¹ Librero and Perez, 1985. Small-scale fisheries in Asia. IDRC-229e.

Table 3. Costs and returns per ha per year of milkfish and shrimp culture in the Philippines¹

	Item		Cost
I.	Costs
	1.	2 200 bangus fingerlings at 400/1 000	880.00
	2.	5 000 prawn juveniles at 400/1 000	2 000.00
	3.	2 bags of urea at 260/bag of 50 kg	320.00
	4.	2.5 bags of 16-20-0 at 260/bag of 50 kg	650.00
	5.	4 tons chicken manure at 550/ton	2 200.00
	6.	4 tons agricultural lime at 400/ton	1 600.00
	7.	Harvesting expenses (1.5blocks of ice at 90/block)	135.00
	8.	Marketing expenses (5 percent from gross sales for fishbroker)	856.80
	Total		641.80
II	Returns - Sales of
	1	1 870 pcs. marketable bangus at 250 g/fish or 467.5 at 18/kg	8 415.00
	2.	4 000 pcs. marketable prawn at 20 g/prawn or 80 kg at 80/kg	6400.00
	Total		4 815.00
III.	Net income		6 173.20

¹ BAC Bulletin No. 1, 1985.

Examples of different small-scale aquaculture operations observed in the ASEAN countries are described below.

2.2 Polyculture in stagnant freshwater pond in Gunung, Jaya, Sukabumi, Indonesia

The project is an earthen pond located about 200 m from the free-flowing carp pond in Gunung Jaya, Sukabumi. It measures 20 m × 40 m with the perimeter dikes measuring 1.5 m high. Water from a creek being used as an irrigation canal enters the pond through a concrete gate. The water depth is kept constant at 1 m.

The owner has not had any formal training in fish culture. He learned the business only by studying the methods used by his neighbours and from the information given him by government extension workers.

The pond is stocked with 50 k each of carp (Cyprinus carpio), Tilapia nilotica and “tambakan”, Helostoma temmincki. The fish seeds individually weigh 60 g, 25 g and 25 g, respectively. Thus, the pond is stocked with 830 carps, 2 000 tilapia and 2 000 tambakan - a total of 4 830; a stocking rate of roughly 60/m² . For a stagnant pond, this is a dense stocking rate and could partially explain the very low production. The fish seeds are bought for Rp 1 300/k, Rp 500/k and Rp 500/k, respectively (US$ - Rp 680) At current rate of exchange these prices would have increased by 50%. On the other hand, selling price of fish in the market also increased accordingly.

The polycultured fishes are fed with rice bran at the rate of 10 k/day, at a cost of Rp 500/day. The feeding is done by the broadcast method by the owner himself. No other feed is given.

All the fishes are harvested after two months of growth. The pond produces an average of 125 k of carp, 65 k of tilapia and 65 k of tambakan. These are sold for Rp 1 500/k, and Rp 625/k, respectively (1982).

It is only during the harvest operations and immediately after that the owner uses hired labour. Five temporary workers are hired for 7 days at the rate of Rp 1 000 plus lunch/worker/day. During these 7 days, the fishes are harvested, the dikes repaired, the bottom cleaned of debris, and the pond stocked with a new crop of the same number of species as the previous one.

Following is a simple computation of the pond's expenses and income every two months. The value of the pond itself is not included.

Operating expenses

Estimate gross sales

Estimate net income

Rp 76 500/2 months or Rp 459 000/year (US$410)