1. Overview

The majority of tidal flats in the coastal zone of the Philippines have been developed for milkfish aquaculture. Three different methods can be used to rear milkfish in brackish-water ponds. The deep-water method, which basically depends on plankton is not common because most fishponds in the Philippines are 70 cm or less deep. The basis of production of the remaining two methods is either blue green microbenthic algae (late-lab in Pilipino) or filamentous green algae (Iumut in Pilipino). A combination of these two methods is usually practiced during a season, in spite of the ecological incompatibility of the benthic and filamentous algae in a onepond environment.36 During the dry season from February to May, when pond salinity is higher, benthic algae thrive. In the rainy season, however, benthic algae die off due to the lower salinity, and filamentous algae become established.

Milkfish culture in the Philippines is largely traditional, with most producers using very few supplemental inputs, such as fertilizers. There are basically two systems of production, those which use no supplemental inputs at all (traditional or extensive) and those which use supplemental inputs (either semi-intensive or intensive}. Productivity per unit area is relatively higher in semi-intensive or intensive systems.

Pond operators stock fry or fingerlings or some combination of these. In many cases where fry are used, the farm is divided into nursery, transition, and rearing ponds through which the stock is progressively moved until it reaches market size four to six months later. The average sizes of each type of pond in seven selected provinces are shown in table 9. For purposes of this discussion, operators of these ponds that rear marketsize milkfish are referred to as rearing-pond operators to distinguish them from the nursery-pond operators who specialize in growing fingerlings.

In addition to using tidal flats, large water bodies (usually fresh rather than marine or brackish) can also be used to grow milkfish in bamboo and net enclosures called fishpens, but so far this has been limited to Laguna de Bay, near Manila. Yields per hectare from fishpens are five to six times higher than those from ponds (see chapter IV).

TABLE 9. Size Distribution of Milkfish Ponds in Seven Selected Provinces

Source: See note 28.
a. Note that average area of nursery and transition ponds is reported only for those farms using this type of devout.
Consequently, farm size by province does not necessarily equal the sum of nursery, transition, and rearing ponds.

There are at present about 176,000 ha of brackish-water ponds devoted to milkfish husbandry in the Philippines. The 1973-1979 average milkfish production from ponds per year was about 115,000 tonnes37 or 650 kg per hectare. In Taiwan, the average is 1,500- 2,000 kg per hectare per year. In the preceding section it was pointed out that the milkfish yields in the two countries per 1 million fry caught are approximately the same. The different yields per hectare, therefore, reflect the more intensive use of land in Taiwan. The low national average yield has been a major concern of the Philippine government agencies responsible for aquaculture development.

Although yields comparable to those of Taiwan have been duplicated by Philippine research facilities and a few private producers, one must be careful not to generalize claims of higher yields to the whole industry. Claims of three- or fourfold increases over the national average yield of 625 kg per hectare per year are misleading, because they reflect the accomplishments of a very small group of successful and innovative farmers. For example, the views of the officers of the Philippine Federation of Fishfarm Producers (renamed the Philippine Federation of Aquaculturists in 1981) are often looked upon as representative of all pro" ducers. Although they do play the role of spokesmen for their industry, one should be cautious in generalizing their public statements to the whole industry. Most milkfish producers have a long way to go before they can produce 2 tonnes per hectare per year from milkfish ponds.

In the past two decades, opening up new lands and production intensification from existing ponds have added equally to increased annual milkfish production. However, recent satellite imagery has shown that there are few areas left which can be brought into production without adverse effects upon other activities in the coastal zone. Contrary to previous estimates made by much less sophisticated means, which indicated that about 500,000 ha of swampland and mangrove are still available for development, the satellite results indicate only 125,000 ha remain. Consequently, measures have been taken to limit the conversion of mangrove areas.

Past government programmes for aquaculture have tended to be predicated upon the assumption of readily available area for expansion. Because of this early emphasis, production intensification methods have only recently been actively promoted by the government, much less adopted by the milkfish farmers. In fact, a close examination of the various credit programmes by the government through the Development Bank of the Philippines and other institutions reveals the almost exclusive emphasis on loans for pond construction, development, and improvement, and little for operating costs, such as the purchase of supplemental inputs.

Because of this heavy infrastructure emphasis, it is not surprising to find studies by various investigators such as Librero27 and Chong38 showing that Philippine milkfish ponds are still largely underutilized. Given the recent satellite finding, the necessity for a shift in the pattern of production and resource use is indicated. Output- or yield-increasing techniques of production from the existing pond area will be needed to boost production.37 _41 This essentially means the adoption of production intensification methods such as the greater use and application of fertilizers. To achieve higher production fertilizers can, within limits, substitute for land. The problem is, therefore, one of attempting to increase the production of milkfish from a more or less fixed land base.

Production intensification methods are basically knowledgeintensive methods of production and these are needed on a global scale if present population trends continue. The production function analysis reported at the end of this section is an attempt to provide timely information on the most profitable input combinations and the corresponding output level. This information would facilitate improvement in resource-allocation efficiency at both the farm and national level, resulting in higher output.

Shang⁴¹ reports that the rapid increase in the cost of fry and fertilizers has imposed a problem on Philippine milkfish producers. Because of this, it is likely to discourage fishpond operators from adopting intensive farming techniques. However, he argues that although the use of inputs can be expensive, their use, if properly carried out can be profitable.

Although supplemental inputs have to be used to improve the productivity of milkfish ponds, the uncertainty of output response due to additional inputs affects a producer's decision on the use, and rates of use, of such inputs. As a result, the producer is naturally interested to know the risks, costs, and benefits involved in using inputs and the possible pay-offs he can expect. In this section, we demonstrate the responses of milkfish output to the various inputs applied.

Note, however, that although inputs are used, they are not uniformly applied throughout the country. Because of this, there is considerable variation in output from province to province. The focus of this section is to explain output variability in terms of the use of inputs. An attempt will also be made to identify the factors which limit the use of inputs. Other possible causes of output variability, which are not discussed in detail here, are differences in environmental conditions such soil type, climate, and pH. This section is based primarily on a survey of 324 milkfish producers in seven provinces conducted in 1979 by the International Center for Living Aquatic Resources Management (ICLARM), the Bureau of Agricultural Economics (BAECON), and the Fishery Industry

Development Council (FIDC) (fig. 32). This survey, hereafter referred to as "our survey," covered farms that are intensively operated (i.e., use supplementary inputs).