A method of partially purifying L-glutamate dehydrogenase, a key enzyme in the biosynthesis of non-essential amino acids, from the muscle of P. monodon juveniles is presented. Enzyme extraction with Tris-acetate buffer, ammonium sulfate fractionation, DEAE-cullulose chromatography, and Sepharose 4B chromatography were used. A 260-fold purification was obtained, but the recovery of enzyme activity was low. Possible modification in the method and the need for further purification are discussed. P. monodon possesses an enzyme which catalyzes the de novo synthesis of glutamate from alpha-ketoglutarate and ammonia. The enzyme has a pH optimum for the reductive amination of alpha-ketoglutarate between pH 8.0 and 8.2. The low Michaelis-Menten constant (1.03 x 10^-4M) of the enzyme for alpha-ketoglutarate strongly suggests the physiological importance of this pathway in P. monodon. Substrate inhibition by alpha-ketoglutarate at high non-physiological levels was observed and discussed. The molecular weight of the native enzyme estimated by molecular sieve chromatography is 320,000 daltons. Subunit studies using SDS polyacrylamide gel electrophoresis suggest that the enzyme possesses a unique molecular organization compared to those derived from other sources.

A total of 551 milkfish eggs was collected by horizontal tows with a fish larval net in the waters around Panay island during the period from April 1976 to June 1979. The maximum number obtained by a single tow was 33 eggs. Most of the eggs were collected from Cuyo East Pass, with some from the waters around the Cagayan Islands and a single egg from the Sibuyan Sea. Almost all the eggs were collected during the period frim March to June, with a peak in April, one month ahead of the peak of fry occurrence. Very often milkfish eggs occurred in shallow waters around islands or close to the coasts, while they were sometimes found at locations remote from land and as deep as 900 m. Water temperatures and salinities at locations shere milkfish eggs were found ranged from 26.7 to 30.8°C and from 32.9 to 34.5 ppt. The eggs were rather evenly distributed from the surface to at least 20 m down. The eggs found in the early morning collections were in the early stages of development; those found later in the day were more advanced. It seems that spawning of mikfish takes place at midnight, and that the incubation period of eggs in the wild is about 20 hours.

The authors surveyed the fishing methods and gears in Panay and smaller neighboring islands in the Philippines in September-December 1979 and in March-May 1980. This paper is a report on the fishing methods and gears used in these islands, with special focus on the traditional and primitive ones.

The survival and growth of milkfish (Chanos chanos ) fry stored in plastic basins at different salinity levels and stock manipulation methods without aeration and fed with hard-boiled chicken egg yolk over a period of 14 days were determined. Results showed that survival rate and increase in body weight did not differ significantly (P > .05) at different salinity levels nor with different stock manipulation methods. Moreover, there was no evidence of a significant interaction between salinity and stock manipulation method. The highest survival rate was 97.8% with stock manipulation 1 and 8 ppt salinity, while the lowest was 95.% with stock manipulation 1 at 32 ppt salinity. Results indicated that there was no need to reduce the salintiy of water used in storing fry in order to obtain higher survival rates as commonly believed. Sufficient food and maintenance of good water quality appeared to be more important than salinity for higher survival of fry during storage.

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.