Knowledge on the feeding activity is basic and very important for rearing fish. The information on the feeding activity rhythm of the animal suggests the proper time to feed it. Many devices have been designed to record the feeding activities of aquatic animals. Some are mechanical devices which are difficult to maintain in good conditions for a long time. None of the present devices can be applied to milk-fish because of its characteristic manner of taking food. In this paper, a new electrical device for recording the feeding activity of milkfish is reported.

Milkfish (Chanos chanos) and prawn (Penaeus monodon) were stocked in 500 m2 earthen ponds from 12 November 1978 to 15 March 1979 at the following combinations: 2000 milkfish fingerlings per ha (treatment I); 2000 milkfish fingerlings plus 4000 prawn juveniles per ha (treatment II); and 2000 milkfish fingerlings plus 8000 prawn juveniles per ha (treatment III), with three replicates per treatment. Highest combined net milkfish and prawn production was obtained in treatment III with 492.1 kg/ha followed by treatment II with 404.1 kg/ha, and treatment I (milkfish only) with 280 kg/ha. Differences in combined net production between treatments III and I and between treatments II and I were statistically significant at the 5% level. Average net production of milkfish alone was also highest in treatment III followed by treatment II and treatment I, although differences were not significant. Average net production for prawn was also better in treatment III than in treatment II but the difference was not significant. However, mean weight of prawn was higher in treatment II compared to treatment III. Average survival rates were high for milkfish in all treatments ranging from 90 to 96%, but low for prawn at around 50% for both treatments. There was no significant difference in survival rates of milkfish among treatments and of prawn between treatments II and III. The competition index between milkfish and prawn at the given stocking combinations was negative indicating a positive, advantageous influence of prawn on milkfish production.

Seven stages in the life history of milkfish Chanos chanos are suggested: embryonic, yolksac larval, larval, postlarval, juvenile, sub-adult and adult stages. These were based on morphological differences and on their particular ecological requirements. The latter include: behavioral pattern, food and feeding habits, and habitat requirements. Throughout the life cycle of milkfish the stronger driving force with determines particular behavioral strategies can be attributed to the evolutionary response of the organism of food distribution (availability) followed by predation pressure.

Penaeus monodon juveniles (P₅₃-P₅₄, 0.45 g) were stocked in 200 m² earthen ponds with water exchange rate of 5-10% daily, and reared for 3.5 months. Stocking density levels of 2.5, 5.0, 10 and 20 prawns/m² were designated as treatments A, B, C and D, respectively. Pelletized formula feed was given daily from the second week of stocking at 10% of biomass and was reduced bi-weekly by 1% to a final rate of 5% of biomass. Significantly, high survival was achieved in treatment A, 98.6% followed by B, 95.3%; D, 87.6% and C, 86.5% (P < 0.05). The final average body weight obtained varied inversely with stocking density. Mean body weight for treatments A and B were significantly higher than those of treatments C and B. Results also showed significant differences among all paired means of the final weights except between treatments C and D.

The skull of the milkfish, C. chanos, is described so that it may be used as a tool in identifying the effect of artificial propagation in terms of skeletal malformations.

Haliphthoros philippinensis sp. nov., isolated from larvae of P. monodon is described and illustrated as new. The fungus grew at a temperature range of 13.5-36.3 C, with the optimum of 29.3-34.5 C. Growth occurred in peptone-yeast extract-glucose broth containing 0.3-7% NaCl, with optimum concentrations of 1-4%. At 8% NaCl concentrations, growth was not observed. Its pH range for growth was 5-11.

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.