A great variety of seaweeds grow abundantly along the 81,000-km coastline of the 13,000 islands comprising the Indonesian archipelago. However, it is only recently that the economic importance of seaweeds has really been appreciated. At present, seaweeds collected in Indonesia are mainly used for food supplement, domestic agar manufacture, and for export. Because of the increasing demands for the carrageenan-containing seaweed, mass cultures have been undertaken in both experimental and production sites established in many parts of the country. These efforts are expected to increase the annual volume of exports from 2000 to 6000 mt. The paper reviews the state and problems of seaweed utilization, development, and farming efforts in Indonesia.

An outline is given of research conducted at the Aquaculture Department of SEAFDEC at Rizal, Philippines regarding algal culture and utilization. Culture methods for both brackishwater and freshwater algae are described and details given of applications of microalgae in the aquaculture industry, which include feed for fish and shrimp larvae.

The bulk of world seaweed production today comes from developed countries in the temperate region, including Japan, China, and Korea. The seaweed production potentials in the developing countries of Asia will have to be explored to meet the increasing world demand. Extensive shallow and farmable reef areas as well as cheap labor highly favor seaweed production. Harvesting from natural stocks is unreliable; efforts should thus be directed toward actual farming of seaweeds. In the Philippines, development of the farming technology on Eucheuma alvarezii and E. denticulatum significantly increased production by the middle of the 70 s. Harvests of Eucheuma from farms and other seaweeds from natural stocks now rank third among the fishery exports of the country. The socioeconomic implications of the development of the seaweed resources in the developing countries of Asia are discussed. The Philippine experience is cited specifically to show the benefits derived from seaweed farming technology.

A brief discussion is presented on the commercial importance of seaweeds in the Philippines, which is mainly concerned with their use as sources of industrial gums such as agar, carrageenan, and alginic acid. Carrageenan as a substitute for microbiological agar and the use of seaweeds as a binder of heavy metal pollutants are examined.

Trentepohlia odorata, a filamentous green alga, grows profusely and imparts an orange color on walls of many high-rise apartment buildings in Singapore. Since bulk cultures are needed in the screening of possible chemicals to control infestation, variations in the growth and development of the alga in the laboratory under different physico-chemical conditions were investigated. Bold's medium either as a liquid or solidified with agar was suitable substrate for the culture of the alga. An acidic growth medium (pH 4.5-6.5) favored the formation of sporangia that developed into yellowish-green colonies, whereas a basic medium (pH 7.5-9.5) produced green colonies and no sporangia. An agar concentration of 0.7% as well as the addition of thiamine to the liquid basal medium enhanced the production of sporangia developing into numerous daughter colonies after two months. High relative humidities increased colony growth and promoted the formation of yellow colonies of cylindrical cells. On walls of buildings, the cells are elliptical to barrel-shaped, bright orange, and possess few sessile sporangia. In cultures where moisture and nutrients are not limiting, cells are narrow and elongated, with the filaments radiating from a central mass, and the sporangia are of the sessile and pedicellate types.

The major problems of fishponds build on acid sulfate soils are low pH; ionic imbalance and toxic levels of aluminum, iron, and sulfate; deficiency of phosphorus and poor response to fertilizer application; slow and poor growth of fish food organisms and fish; erosion of dikes; and in some cases fish kills. For economic operations and to remedy the problems of poor algal growth, fish kills and low yields, the acid in the pond bottom and dikes has to be neutralized or removed. A repeated sequence of drying, tilling, and flushing with seawater is a cheap, fast, and effective reclamation method that can be done in one dry season. Following this method, the dry soil pH improved; exchangeable aluminum, pyritic iron, active iron, active manganese, and sulfate decreased; and available phorphorus improved. The values for alkalinity, phosphate, aluminum, iron, and sulfate in the pond water improved greatly. Fish production was about three-fold more in reclaimed ponds (375-510 kg/ha) compared with the control ponds (50-173 kg/ha).

Aspects of the time, place, and mechanism of occurrence of milkfish (Chanos chanos ) fry, defined as the postlarvae 10-17 mm in total length and 3 weeks of age are considered. Fry occurrence shows seasonal patterns that differ by latitude. In the Philippines (15-21 degree N), fry appear earlier in the south (December-January) and later in the north (March-April); they disappear earlier in the north (July-August) than in the south (December-January). Greater numbers of fry occur in shore waters during the full moon and new moon periods, largely as a consequence of the greater spawning activity during the quarter moon periods. Fry catch by various active and passive filtering gear is greater at floods and high tide than at low and ebb tide. Milkfish fry occur in and are collected mostly from sandy beaches, particularly the surf zone and in and around river mouths. They appear to be distributed mostly near the surface, with greater numbers nearer shore. It appears that larvae smaller than 9-10 mm are distributed in midwaters, but once they reach this size they come up and are carried inshore by tidal and wind-driven currents.

In culturing milkfish (Chanos chanos ) to marketable size, the fry (total length = 12-15 mm) are usually reared first in nursery ponds or pens (hapa nets) until they become fingerlings (total length = 2 cm or more). The fingerlings are then transferred to the grow-out ponds or pens where they are reared to marketable size. In some countries like the Philippines, fingerling production has become an industry by itself. This paper reviews the state of the art and constraints to and suggests future research directions for milkfish fingerling production in nursery ponds and pens.

Milkfish (Chanos chanos ) has been extensively cultured in Indonesia, Taiwan, and the Philippines. At present, the only source of fry for fish farmers is the coastal waters during the spawning season. The supply of fry is therefore often irregular and inadequate. Since the early 1970s attempts have been made to breed milkfish in captivity, particularly in Hawaii, Taiwan, and the Philippines. This paper reviews the progress problems and suggested future research direction of the following areas: induction of ovulation/spawning, sperm preservation, larval rearing, and induction of gonadal maturation.

This paper attempts to explain empirically the entire milkfish (Chanos chanos ) industry in Taiwan, convering 1) the gathering and marketing of milkfish fry - the procurement subsystem; 2) the production of milkfish fingerlings for the baitfish industry; 3) the production of market-size milkfish - the transformation subsystem; and 4) the marketing of market-size milkfish - the delivery subsystem. A constant elasticity of substitution production function is used to estimate the input-output relationship for baitfish and market-size production systems, with all inputs classified into labor and capital. An important finding is that the elasticity of substitution between labor and capital exceeds unity, indicating rather easy substitution between the two inputs in the milkfish industry in Taiwan. The area for aquaculture has expanded rapidly during the past two decades, but the milkfish production area has remained at 15,000 ha and yields have increased slowly compared with those of other cultured species.