Most of the fish research at SEAFDEC AQD in 1992-1994 was on milkfish. Studies were conducted on year-round spawning through hormonal or environmental manipulation; optimum lipid and protein levels and ration size for captive broodstock; and the influence of spawner age on reproductive performance. The economics of hatchery operations, alone or integrated with broodstock as a commercial enterprise, was assessed. Mass production of larvae was refined with the use of commercial or SEAFDEC-formulated larval diets. Alternative rearing schemes in large tanks and ponds were tried. Hatcheryproduced and wild-caught larvae were compared in terms of growth and production in experimental nursery and grow-out ponds. Supplemental diets for brackishwater grow-out culture were formulated. Studies on broodstock management of grouper Epinephelus spp. included lipid enrichment of the diet and hormonal induction of sex inversion. Seed production techniques were developed but survival rates were low. Grouper culture was found economically feasible in experimental ponds with 'trash' fish as feed. The mangrove red snapper Lutjanus argentimaculatus was successfully induced to spawn with injection of human chorionic gonadotropin. Initial larval rearing trials were successful but survival rates must be improved. Hormonal manipulation of spawning of the Asian sea bass Lates calcarifer allows seed production during most of the year. Photoperiod manipulation leads to maturation of females, but not males, beyond the natural breeding season (April-November). Nursery rearing of 9 mm juveniles is feasible in floating net cages with night lights that attract food zooplankton. The requirements of sea bass for lipid, protein, carbohydrates, and essential amino acids were determined. In the rabbitfish Siganus guttatus, weekly injections of luteinizing hormone releasing hormone analogue (LHRHa) sustains milt production for three weeks. Thyroid hormones injected into broodstocks improved the growth of larvae to day 7. Induced spawning techniques for the Asian catfish Clarias macrocephalus were refined by determining the seasonal responsiveness to LHRHa and pimozide injections and testing for pheromonal induction of spontaneous spawning. The optimum insemination rate was determined and egg hatchability was enhanced by removal of the adhesive coat before incubation. Several practical diets for catfish during grow-out culture were tested against 'trash' fish. The broodstock management for bighead carp Aristichthys nobilis was studied. Cage-reared juveniles from cage-reared broodstock showed the best growth. To improve the reproductive performance, the broodstock diets were supplemented with vitamins A, C, and E. Research on tilapias focused on genetics and strain selection. Several strain testing procedures for Nile tilapia were evaluated in their efficiency to detect economically important strain differences. Reference lines were developed from two existing red tilapia strains to measure and reduce the effects of uncontrolled nongenetic variables in strain evaluation experiments with Nile tilapia. The tolerance of two Nile tilapia strains to heavy metals was similar when gauged by the 24-hour and 96-hour lethal concentration and by fish growth, survival, and reproductive performance. In a separate study, four strains of red tilapia showed generally higher seed production when reared in tanks than in cages. Improvements in the feed and feeding management for Nile tilapia were also studied. Intensive tilapia farming and feeding have led to oxygen depletion and fish kills in Sampaloc Lake. To rehabilitate the lake, it is imperative to reduce the farming area from 30 to 6 hectares; stop the use of commercial feeds; and remove the water hyacinths and other debris. Fish kills in Laguna de Bay have also become serious in recent years, and a review of the occurrences, losses, and possible causes is currently being conducted. Studies on the epizootic ulcerative syndrome of snakeheads in Laguna de Bay have yet to pinpoint the pathogen. Skin lesions in tilapias in several ponds and lakes in the country were found to be due to bacteria.

Mollusc research at the Aquaculture Department of the Southeast Asian Fisheries Development Center from 1989 to 1991 was primarily focused on the highly exploited window-pane oyster, Placuna placenta Linnaeus. Other species studied were the saddle-shaped oyster, Placuna sella, the slipper-shaped oyster, Crassostrea iredalei, and the green mussel, Perna viridis. Research on P. placenta aimed to develop techniques in seed production (broodstock maturation and induced spawning), transplantation, and stock assessment and restocking of depleted natural beds. The annual variations in the reproductive activity, condition index, and proximate composition of P. sella were determined. A socioeconomic study of oyster (C. iredalei) and mussel (P. viridis) farming practices in western Visayas, central Philippines is on-going and will provide information on current culture methods and their profitability. An inventory of mollusc researches conducted in the Philippines has been done and the culture techniques and research gaps are being reviewed and identified. This information will guide further research on molluscs in the Philippines.

Research activities on tilapia focused on Oreochromis niloticus and red tilapia. Experiments include developing new experimental and statistical procedures for strain evaluation, development of a stable reference strain, development of a high-yield red tilapia strain through introgressive hybridization, comparison of fish growth in different environments relevant to aquaculture, development of an index for routine monitoring of salinity tolerance of existing tilapia strains/experimental stocks, evaluation of nutritional requirements of red tilapia, and determination of heavy metal contents of tilapia in Laguna de Bay, Luzon, Philippines. Research on carp (Aristichthys nobilis) and catfish (Clarias macrocephalus) were focused on improvement of methods for induced spawning, development of seed production techniques, and nutritional requirement of bighead carp fry and broodstock. Research on carp (Aristichthys nobilis) and catfish (Clarias macrocephalus) were focused on improvement of methods for induced spawning, development of seed production techniques, and nutritional requirement of bighead carp fry and broodstock.

This paper reviews studies conducted on milkfish (Chanos chanos), rabbitfish (Siganus guttatus), and mullet (Mugil cephalus) at the SEAFDEC Aquaculture Department from 1968 to 1991. Milkfish studies focused on hormonal induction of off-season gonadal maturation, dietary manipulation of milkfish broodstock to improve egg and larval quality, improvement of larval rearing techniques for mass fry production and technology transfer to the private sector, and search for a low-cost, practical diet for milkfish and a supplemental diet to increase pond production. Preliminary success on alternate feed for larval rearing and spontaneous maturation of milkfish in concrete tanks may help alleviate milkfish fry supply in the future. Studies on rabbitfish centered on improvement of larval survival and search for the optimum diet for growth of rabbitfish fry and juveniles reared in ponds. The difficulty in rearing rabbitfish larvae due to high mortality at first week after hatching hinders the development of the rabbitfish industry. Research involving mullet was solely on the establishment of broodstock for fish propagation.