An extensive ecological survey was conducted in the Philippines to study the feeding of milkfish, Chanos chanos Forsskal. Types of environments examined included coral reefs, lagoons, mangrove and nipa swamps as well as estuarine systems. It was concluded that organic detritus was the basic nutrient for juvenile milkfish and that depositional environments constitute important nursery and feeding grounds for this spcies. The main pathway of energy flow in these coastal ecosystems through the detritus rather than the grazing pathway. The feeding of milkfish was described in terms of habitat structures, stomach content, feeding chronology and feeding behaviour. The result suggests that a better understanding of the function of the ecosystem will help to improve present aquaculture practices as well as guidelines for resource management.

The mass culture of the harpacticoid copepod, Tisbintra elongata, indigenous to Panay Island were conducted, feeding them on several kinds of food materials. Salinity tolerance as physiological parameter was also examined. At the same time their efficiency as food for milkfish larvae was evaluated. The highest density of 10.5 individuals/m/ was obtained in copepods fed on rice bran and fermented fish solubles at rates of 0.125 to 0.25 and 0.16 mg/indiv./day respectively. The provision of shelter as habitat was also supplementary for growth. This species of copepod was found to be euryhaline, and could grow to high densities in waters hypersaline to their natural habitat. Statistically, no significant difference of growth was observed between the milkfish larvae fed on this species and Artemia nauplius. However, comparatively stable results were obtained using Tisbintra as food. In this rearing of milkfish larvae, those larvae whose sizewas 12.3 to 13.5mm in body length were considered to be just prior to morphological change.

Feeding experiments were conducted on Penaeus japonicus larvae using Chaetoceros gracilis plus Artemia nauplii, an artificially prepared diet (Diet-B), and two commercial feeds (Tapes and mysid meals) in a randomized complete block design with two replicates per diet. The artificially prepared diets were dried and ground to size 10 to 50 microns and fed to the larvae. The larvae were reared in round plastic aquaria each containing 5 liters of filtered seawater. Each aquarium was stocked with 250 larvae and provided with aeration. The larvae were reared from zoea (Z₁) to mysis (M₃) stage and growth was measured daily. The highest survival rate of 34.2% was obtained when the larvae were fed with Diet-B. C. gracilis plus Artemia nauplii feeding gave a survival rate of 21.6%. On the other hand, growth measured in terms of development, was fastest using C. gracilis plus Artemia nauplii. Larvae metamorphosed into stage in 7 days with an average gain in length of 0.46 mm/day. Diet-B feeding resulted in a comparable growth, the larvae reaching M3 stage in 8 days with an average gain in length of 0.30 mm/day. Analyses of the chemical composition of the diets showed no definite relationship between diet composition and growth and survival rates of the early larval stages of P. japonicus. Results obtained in this study demonstrate that the early larval stages of P. japonicus can be reared with feeding of Diet-B. Since the chemical composition of the diet is known, it can be used as supplemental data for larval feed development and nutritional requirements studies for the early larval stages of P. japonicus and/ or other penaeids.

Penaeus monodon postlarvae with mean weights of 2 to 3 g were fed shrimp head meal (Diet B), fish meal (Diet C), mussel (Diet E), a combination of equal amounts of shrimp head meal and fish meal (Diet A) or one part shrimp head meal and 2 parts fish meal (Diet D) as primary sources of protein. The larvae were reared for 30 days in cylindrical fiberglass tanks containing 150 l of aerated seawater. Mean weight gains were significantly highest among those fed combinations ofish meal and shrimp head meal. Diets A and D, 0.88 g and 0.59 g, respectively. Mean weight gains among those fed one main source of protein, Diets B, C and E were not significantly different from each other and were very low. Highest survival rate was observed among hose fed Diet C (85%) and the lowest recorded (45%) was obtained from those fed mussel. Those fed Diet B grew the slowest and had the lowest survival rate of the groups given formulated diets. Shrimp head meal and fish meal complement each other in the diet formulations. Shrimp head meal alone does not provide for growth and survival, but fish meal can provide for high survival rate. The addition of shrimp head improves the diet. Cholesterol which is present in shrimp could have caused the difference.

Trachypenaeus villaluzi a new species of penaeid prawn from the Philippines is described in detail and compared with the related species. The new species is characterized by the following features : Mastigobranchia are present on the 2nd and 3rd pereiopods, but absent on the first ; anterior plate of thelycum is deeply concave ; the lower margin of the distolateral projections of the petasma is concave. It is also suggested that Trachypenaeus asper Alcock Should be considered as a valid species instead of being treated as a synonym of T. curvirostris (Stimpson).

For a period of one year beginning December 1977, drift card experiments were conducted off the western and southwestern coasts of Panay Island to determine the surface currents in the area. Of a total 2,384 drift cards released during the study, 382 (16.02%) were recovered, 92% of them within 30 days following dispatch. The surface currents in the study area are strongly influenced, in direction and speed, by the prevailing monsoon winds. During the NE monsoon period, the surface currents move away from the coast; during the SW monsoon, toward and/or parallel to the coast. Based on the results, the probable movement and transport of milkfish eggs and larvae from the spawning ground to the fry collection ground are also discussed.

Lagenidium scyllae , a marine mastigomycete from the ova and larvae of the mangrove crab, is described and illustrated as new. The fungus grew at a temperature range of 16-42 C, with an optimum at 22.5-31.8 C. It grew well in peptone-yeast-glucose (PYG) broth containing 2-3% NaCl. In PYG-sea water medium, it grew at a pH range of 5-11.

The postlarvae were maintained in 5-l round plastic aquaria and provided with aeration for a 28-day feeding period. Highest survival rate of 100% was obtained when the postlarvae were fed with Diet-B. Growth, in terms of weight and length was highest in postlarvae fed with Kyowa Hakko and mysid feeds. Using T. philippinarum as control, this experiment showed that feeding with Diet-B, Kyowa Hakko and mysid feeds resulted in similar or better growth and survival rates of P. japonicus postlarvae.

This paper discusses present prawn culture practices in the Philippines, as well as the experiments which are conducted at the SEAFDEC Aquaculture Department by reviewing production of fry, production of juveniles in nursery ponds, growing prawn in rearing ponds, and present problems of prawn culture in the Philippines.

The role of hormones in the controlled reproduction of a few test fishes is well documented. However, information on the mechanisms of endocrine regulation of ovulation in cultivated warm-water fishes is very meagre. Hormones, especially the gonadotropic hormones of piscine origin, are increasingly being used in modern aquaculture to produce the seed of many important cultivated fishes. While chorionic gonadotropin and other exogenous mammalian hormones are used in spawning the channel catfish, fish pituitary hormones are usually needed to induce spawning in the difficult-to-spawn Asiatic carps. In mullets, however, either homoplastic pituitary gland or human chorionic gonadotropin (HCG) or a mixture of HCG and a threshold dose of the former is ordinarily injected to precipitate spawning. Of late, semi-purified salmon gonadotropin (SG-G100) has been used to induce spawning in several species of food fishes. While several marine fishes have been artificially bred by administration of hormones, induced spawning of the milkfish, C. chanos has been tried with little success. The milkfish is a widely distributed food fish extensively cultivated in ponds in Southeast Asia. Recently, significant results have been obtained in spawning mature milkfish captured from the wild by hormone injections. The experiments conducted on induced breeding of milkfish leading to the successful fertilization and hatching of milkfish eggs are briefly described.