Reproductive performance of pond-reared tiger shrimp given astaxanthin (100 mg/kg diet) and Vitamin A (20,000 IU) for 61 days was assessed in a 2x2 factorial experiment in a completely randomized design. Mean gonad index (the degree of gonadal development) of shrimp fed diets containing astaxanthin and/or vitamin A (3.08-3.30) was significantly high (P< 0.01) compared with that of the control (2.36). However, shrimp fed astaxanthin supplement had a significantly higher (P < 0.01) mean gonad index than those fed diet with vitamin A. Interconversion of both supplements was highly detectable during gonadal development of shrimp. Fecundity (3.2 - 7.3 x 10 eggs/female) and hatching rate of eggs (0.0 - 5.7%) were not significantly affected (P > 0.05) by the addition of astaxanthin and/or vitamin A in the diet. The results suggest that astaxanthin and vitamin A supplementation significantly improve gonadal development and spawning but not fecundity and hatching rate. Astaxanthin and vitamin A interconversion occurs more towards the astaxanthin pathway. Hormonal changes during eyestalk ablation could have influenced this interconversion. Further, astaxanthin is directly involved in the gonadal development of pond-reared shrimp broodstock. High maturation rate (60%), spawning rate (36%) and early occurrence of first spawning (14 days after eyestalk ablation) were observed in shrimp fed astaxanthin supplement.

Considerable progress has been made In the field of fish nutrition during the past two decades. Nutritional data for some species such as trout, salmon, channel catfish, and common carp are well established and efficient feeds have been developed. However, nutrition of fish species commercially Important In the Southeast Asian region is still in its infancy and much of the existing Information needs further verification. Basic requirements for some of the 5 major nutrient classes and energy have been determined. However, knowledge of larval and broodstock nutrition is limited. The role of nutrition in immune function and disease resistance should be investigated. Nutritional value and nutrient bioavailability of local feedstuffs as well as methods for improving the nutritional quality of inferior feedstuffs should be given priority. The potential benefits of additives, and harmful effects of toxicants and anti-nutritional factors need to be assessed. The effects of the diet on product quality are becoming increasingly important, but work on feed processing technology in relation to the physical and nutritional quality of feeds is lacking. Emphasis must also be given to the improvement of feed performance and feeding strategies for various life stages under different production systems and management practices in order to reduce production costs and minimize the negative impact of feeds on the environment.

The incidence of unexplained mortalities among marine finfish in the Philippines has been increasingly observed. Considering that outbreaks of viral infections affecting similarly cultured marine fishes such as grouper and seabass were reported in many countries, a comprehensive diagnostic program to meet the challenge was initiated at the Aquaculture Department, Southeast Asian Fisheries Development Center (SEAFDEC-AQD)with funding from the Japanese Trust Fund Fish Disease Project. This activity was further boosted by the Japan International Research Center for Agricultural Sciences (JIRCAS). Overall, the program involved the staff of the marine finfish hatchery and the Fish Health Section. Cases of unexplained mortalities observed in the hatchery were referred to the Fish Health Section. Detailed information on the culture histories of each case were provided by the hatchery staff. Diagnostic tests were performed on each case and those with potential indication of viral etiology were processed for virus detection. Presumptive diagnosis of viral infections was based on typical signs, cell culture isolation histopathology and in-vivo pathogenicity tests. Confirmatory tests to identify specific viruses include RT-PCR, FAT and electron microscopy. The highlights of outbreaks of viral nervous necrosis and other virus-associated infections among marine finfish at SEAFDEC-AQD are presented.

A study aimed at obtaining a biological control agent against bacterial diseases, specifically luminescent vibriosis, of hatchery-reared shrimps and crabs was done to find an alternative for chemotherapy as a disease prevention and control method. Bacteria were isolated from crustacean rearing environments where luminescent vibrosis was not observed, from natural food, and from various feed ingredients. From hundreds of purified strains, 80 bacterial isolates were tested in one-on-one mixed cultures in seawater for their ability to suppress the growth of luminescent Vibrio harveyi. Of the 10 isolates exhibiting that capability, two strains were further studied: C1 from chlorella culture and P9 from a commercial probiotic preparation. However, due to the indigenous nature of C1 strain from the unicellular alga Chlorella sp. and the ease in distinguishing it from other bacteria owing to its colony morphology, more tests were done on C1 strain. To determine the suitability of C1, and to some extent P9, as biocontrol bacteria, their pathogenicity against crab larvae and shrimp postlarvae, and their ability to become associated or incorporated into the larvae were determined. Incorporation into the rotifer, Brachionus, was also tested. Due to the positive results obtained in the incorporation experiments, the growth of strain C1 in microbiological media and unrefined media prepared from agricultural by-products was also tested.

The SEAFDEC Aquaculture Department studies on mangrove-friendly aquaculture (MFA) can be categorized under two models: a) mangrove filters where mangrove forests are used to absorb effluents from high-density culture ponds, and b) aquasilviculture or the low-density culture of crabs, shrimp and fish integrated with mangroves. In a study using the first model, shrimp pond effluents were retained in an enclosed mangrove area prior to release to receiving waters. Nutrients and other water quality parameters, and bacterial levels were monitored in the untreated effluents and post-mangrove water. In the second MFA model, mangrove pens and ponds installed in old growth and newly regenerating mangrove sites in Aklan, central Philippines were stocked with mud crab Scylla olivacea/S. tranquebarica and shrimp Penaeus monodon. Investment costs, survival and production, and cost-return analysis for the pens and ponds are reported in the paper. Aside from the aquasilviculture trials in collaboration with local government units, other activities in the Aklan mangrove sites are the survey and mapping of the 75-ha area in Ibajay, construction of a treehouse, and the educational use as field site by Coastal Resource Management trainees of SEAFDEC Aquaculture Department and field biology students of the University of the Philippines in the Visayas.

This paper reviews the progress of mollusc and seaweed research at SEAFDEC AQD from 1995 to 1999. Because of the pressing need for seedstocks for stocking, research on the donkey s ear abalone, Haliotis asinina focused on the development of seed production and culture techniques. To improve the spawning performance and egg/larvae production of captive broodstock studies on reproductive biology, management of broodstock and development of diet were conducted. Studies to refine techniques for post-larval settlement and metamorphosis and development nursery rearing techniques were carried out to increase production of abalone juveniles. An artificial diet has been developed to enhance growth rates of juveniles during nursery as well as grow-out. However, since long-term use of artificial feeds did not favor the growth and survival of abalone during grow-out culture in tanks due to difficulties in maintaining water quality, sequential feeding with artificial diets and then seaweed Gracilariopsis bailinae seemed more practical. Broodstock development and seed production were the major research areas for the window-pane oyster Placuna placenta. Gonad development was enhanced by feeding a mixture of high densities of Isochrysis galbana and Tetraselmis tetrahele at a 3:1 ratio. P. placenta larvae reared with Isochrysis as feed showed best growth and survival. Settling stage was reached after 14 days of rearing. A salinity of 34 ppt was optimal for larval survival. Poor growth and survival of larvae was observed at low (10 ppt) and high salinity (40 ppt) levels. Re-stocking immature adults and juveniles was conducted in a depleted coastal bed to evaluate potentials for recruitment of the window-pane oyster. After 91 days, a survival rate of 51% was observed among immature adults. No juveniles survived after re-stocking. Studies on seaweeds focused on three economically important genera of red algae: (1) Gracilaria, (2) Gracilariopsis, and (3) Kappaphycus. These studies are in recognition of Gracilaria and Gracilariopsis as agarophytes and Kappaphycus as carrageenophyte having significant roles in the seaweed industry. Research studies therefore aimed to optimize culture techniques for and to develop environment-friendly aquaculture of these seaweeds. Optimization of biomass production was attempted by manipulating the nutrient environment, biomass density, the proportion of harvested biomass, and crop quality for conversion to agar and carrageenan. The use of G. bailinae as a bio-filter focused on the capacity of the seaweed and its agar to sequester heavy metals like cadmium copper, lead and zinc after exposure to various concentrations of these metals. Likewise, excess levels of nitrogen and phosphorus in a finfish broodstock tank with re-circulating water were reduced, demonstrating the efficiency of the seaweed as a bio-filter in aquaculture. Eco-physiological studies of Gracilaria changii, G. coronopifolia, G. firma, and G. bailinae involved the mass production of spores-in vitro as a possible source of seedlings for outplanting. A socioeconomic survey of Kappaphycus culture in the Philippines revealed that, although expensive, deep-sea farming of K. alvarezii using the multiple raft long-line technique was more productive and profitable than the traditional mono-line or the popularly practiced hanging long-line technique.

Studies on tilapias focused on the refinement of strain comparison methods, refinement and pilot-testing of broodstock improvement procedure, selective breeding and evaluation of red tilapias, genetic variability determination in hatchery-bred tilapia and the development of criteria for tilapia fingerling quality assessment. On carps, feeding of bighead carp (Aristichthys nobilis) to enhance reproductive performance was done and stunting was applied as a technique in broodstock development. Studies on the tolerance of bighead carp fry to low salinities were conducted. Free-living nematodes were tested as alternative larval food. The culture potential of grass carp in lake-based cages was also determined. Research on the native catfish (Clarias macrocephalus) focused on endocrine studies during the final stages of maturation. Hatchery techniques were refined by identification of factors that increase fry production. Practical diets were developed for broodstock, hatchery, nursery and grow-out phases. A collaborative project on the ecological impact of African catfish (C. gariepinus) introduction in natural waters was undertaken. The occurrence of EUS (epizootic ulcerative syndrome) among wild fishes in Laguna Lake decreases the marketability of both wild and cultured fishes from the lake. Hence, the bacteria and virus associated with EUS and their virulence, modes of disease transmission, developmental stages of dermal lesions and hematological changes in severely affected fish were studied. Laguna Lake, where fish catch and aquaculture production contribute significantly to the country s total freshwater fish production, has been the focus of extensive ecological research in collaboration with other local and foreign research and academic institutions.

Research on marine fishes at SEAFDEC/AQD from 1995 to date was mostly on milkfish Chanos chanos. Studies focused on the refinement of broodstock and seed production techniques to improve egg and larval production as well as to eliminate morphological deformities in hatchery-bred fry. A verification study with former shrimp hatchery operators demonstrated the technical and economic viability of the AQD-generated milkfish hatchery technology. Production and efficiency of semi-intensive grow-out in ponds were enhanced by the use of formulated feeds and appropriate feeding scheme. Milkfish farming in the Philippines was critically reviewed and recommendations to sustain milkfish culture production were made. Tobacco dust and metaldehyde formulation were proposed as alternatives to organotin-based pesticides in controlling the population of pond snail. The growth hormone of milkfish has been isolated and purified. Addition of highly unsaturated fatty acid (HUFA)-rich oils in the diet did not improve the quality of spawned eggs of grouper Epinephelus coioides. A protocol for the intensive larval rearing of grouper was developed based on the results of several studies. A semi-intensive seed production method using copepod nauplii during the early feeding stages was also developed as an alternative to intensive method. Metamorphosis of larvae was significantly accelerated by exogenous thyroid hormones. Nutritional studies to reduce the amount of fish meal in grouper diets are in progress. Groupers grown in ponds or cages harbor a variety of parasites. Biochemical criteria to assess the quality of spawned Asian sea bass Lates calcarifer eggs was characterized. Diaphanosoma or other copepods may be an alternative or supplemental live prey to Artemia during sea bass larviculture. A practical diet for sea bass culture was developed. Studies to determine the essential amino acid requirements of sea bass are about to be completed. The effects of immuno-stimulants in sea bass are presented. Induced and natural spawning of mangrove red snapper Lutjanus argentimaculatus in concrete tanks or floating net cages has been documented. An improved larval rearing method has been developed using screened rotifers during the early feeding stage of the larvae. Exogenous thyroid hormones have advanced metamorphosis of larvae. A practical diet for snapper is under development. Research on rabbitfish Siganus guttatus were geared to developing tools for growth enhancement. Pituitary growth hormone (GH) has been cloned, allowing the production of recombinant rabbitfish GH. Rabbitfish prolactin, somatolactin have also been purified. Studies on marine ornamental fish focused on two species of seahorses, Hippocampus kuda and H. barbouri, and on blue tang Paracanthurus hepatus. Progress on the biology, breeding, and seed production of seahorses are presented. Successive natural spawnings of blue tang in concrete circular tank have been recorded.

SEAFDEC Aquaculture Department (SEAFDEC/AQD) is mandated to develop human resources and disseminate and exchange information in aquaculture. Towards this direction, AQD’s recent thrusts are focused on the verification, packaging, and commercialization of the technologies developed through research. AQD disseminates and exchanges information on aquaculture research and technology through training, extension services, community-based projects and mass media. Through these strategies, AQD aims to reach out to more clientele which include among other sectors the private industry, research and academic institutions, regional and international organizations, policy-makers, non-government organizations, resource managers, SEAFDEC member-countries, local and national government and the fisherfolk. For the past two years, the scope of training courses and extension services of AQD have been expanded from technological viability to sustainability i.e., technological feasibility, economic viability, environmental sustainability and social equity. To attain sustainable aquaculture the following elements were considered: status of technology, conditions of the coastal resources, socio-economic attributes of the community and other stakeholders and institutional arrangements on sustainable aquaculture. Starting 1997, subjects on mangrove-friendly aquaculture and coastal resource management were incorporated into the curriculum of training courses. These courses are the following:

• Third Country Training Program on Coastal Aquaculture and Resource Management for trainees from Asian countries
• On-site Training on Sustainable Aquaculture and Coastal Resource Management in Vietnam
• Sustainable Aquaculture and Coastal Resource Management for extension workers and fishery school teachers

In terms of technology verification and extension, the culture of mudcrab (Scylla sp.) was tested in mangroves or tidal flats with existing mangroves in two different sites (Puerto Princesa, Palawan and Kalibo, Aklan) in collaboration with local government units and the fisherfolk. These activities started in 1997 and will be replicated in other areas of the country. Also in 1997, AQD published and distributed an issue on integrated farming with aquasilviculture in its SEAFDEC Asian Aquaculture newsletter. In 1998, AQD produced a 12-minute video on Conserving Mangrove Resources.

Recent statistics of fishery production in the Philippines reveal outputs that are either declining (municipal fishery) or levelling off (commercial fishery and aquaculture). These trends are, in part, a reflection of the serious effects of unregulated economic activities in the coastal zone. The degradation of coastal ecosystems means a loss of livelihood among many communities of impoverished fishers as catches from municipal waters have declined over the years. Considering that mangroves, seagrasses, and coral reefs are vulnerable to anthropogenic perturbations, several development strategies are presented to meet the twin issues of ecosystem conservation and food security for coastal fishing communities. Mariculture, searanching, habitat alteration and restoration are a few of these strategies. Our recent experience in village-based reef resource management in Mararison Island, central Philippines may likewise be a viable option in the management of shoreward ecosystems (mangroves and seagrasses). In particular, the establishment of a marine reserve in the island may find some relevant applications in mangrove management and development.