Straminipiles are common inhabitants of marine, estuarine and freshwater aquatic environments. In mangrove habitats, halophytophthorans and thraustochytrids are abundant, both in tropical and sub-tropical areas. Their abundance is attributed to their wide tolerance to environmental parameters such as salinity and temperature, and their ability to produce abundant zoospores. Fallen mangrove leaves supply the bulk of organic material in any mangrove habitat. Straminipiles are one of the initial colonizers of fallen mangrove leaves. The ability of their zoospores to respond chemotactically to nutrients released by the leaves, and to attach firmly on the substrata surface by the release of adhesive materials, make them highly competitive in the colonization process. Thus, they are reported to play significant role in the microbial degradation of fallen mangrove leaves. Moreover, these organisms, especially thraustochytrids, are producers of high amounts polyunsaturated fatty acids (PUFAs). Therefore in the degradation process, they consequently enrich the nutrient content of the leaves for the benefit of other organisms at higher trophic levels, making mangroves an excellent nursery grounds for many fish and crustacean species. Some species of thraustochytrids are also used in the commercial production of PUFAs, for use in aquaculture specifically in larval rearing of marine fish and crustaceans.

The significant role of aquaculture in providing food security has been recognized, not only through its contribution to food supply, but also through the promotion of economic and social well-being. Aquaculture is also considered as a relatively recent and underdeveloped sector as compared to agriculture and animal husbandry, and there is a huge, unfulfilled potential in many countries, particularly in the region. The recently concluded ASEAN-SEAFDEC Conference “Fish for the People” highlighted the importance of sustainable fisheries for regional food security, and the need for comprehensive and cooperative efforts, resolutions and plan of actions among all stakeholders. With the projected shortfall in the supply of fish and fishery products to meet the demands of an ever-increasing population, aquaculture is looked upon as a sustainable source of renewable food resources. One of the main programs of the SEAFDEC Aquaculture Department (AQD) is geared towards the development of sustainable aquaculture that is technically feasible, economically viable, environment-friendly, and socially equitable. An important subprogram is the development of environment-friendly aquaculture technologies and practices. The objectives of the subprogram are: 1) to develop and promote efficient aquaculture systems and designs for maximum sustainable productivity; 2) to devise and determine appropriate design, equipment, and operation and management practices that optimize utilization of resources and inputs, minimize adverse impacts on the environment, and sustain biological/ecological diversity; 3) to demonstrate, verify, adopt, refine, and promote proven aquaculture technologies and practices; and 4) to advance the social, economic, cultural, and policy importance of the aquaculture sector at the local, national, and regional level. At present, the main research areas are in nutrient dynamics of aquaculture systems, feed and waste management, development of culture systems, including bioremediation strategies, conservation and sustainable utilization of resources for aquaculture, and socio-economic and policy issues in aquaculture. In addition, verification and refinement of developed aquaculture technologies, in support of re search and training activities, are conducted to explore the potential of aquaculture technologies for commercial adoption and demonstrate appropriate technologies and responsible aquaculture practices. The paper presents an overview of current research activities by the author, and with involvement of other researchers at SEAFDEC AQD, including future plans under this and related programs.

This paper provides information on grouper research activities that have been carried out in SEAFDEC AQD. It covers various aspects such as broodstock management, seed production, nursery and grow-out culture techniques.

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.

The 'green water culture' of the tiger shrimp, Penaeus monodon, is an innovative culture technique for the grow-out rearing of shrimps. This culture method involves the use of rearing water of tilapia for the rearing of tiger shrimp in grow-out ponds and on the polyculture of shrimp with tilapia. This culture technique was reported to present disease outbreaks attributed to luminescent Vibrio. To understand the possible mechanisms of luminous Vibrio control in the green water culture system several studies were conducted. This review summarizes the highlights obtained so far from these studies consisting of a) effect of rearing waters from tilapia culture and shrimp cultured with tilapia on Vibrio harveyi; b) estimation and preliminary identification of cultivable bacteria, fungi and phytoplankton flora associated with the 'green water culture' system and c) detection of anti-Vibrio harveyi metabolites from bacteria, yeast, filamentous fungi and phytoplankton indigenous to the 'green water culture' system.

The Asian catfish, Clarias macrocephalus is a native but fast disappearing species in the Philippines. It is locally named as hito to Tagalogs, paltat to Ilocanos, pantat to Cebuanos and Ilongos, and Ito to Pampangueños. They are called catfishes because they posses whisker-like structure near their mouth called barbells. Among the Clarias species Clarias macrocephalus is preferred because of its tender and delicious meat. Many people believed that the disappearance of the native catfish is due to interbreeding with Thai catfish, Clarias batrachus and the rampant use of pesticides in the ricefields that "poison" the breeding grounds of this species. At SEAFDEC/AQD, standardized techniques were developed in the laboratory for breeding and seed production of this species. Verification studies are on going on nursery techniques in tanks and ponds and grow out culture in ponds. The topics to be discussed are mostly based on SEAFDEC's research studies and hands-on experiences on the native catfish Clarias macrocephalus.

Marine fish production has increased dramatically in the past ten years and majority of the cultured species were produced in Asia in 1992. Increase in production was accompanied with concerns on increasing outbreak of disease, degradation of environment as a consequence of culture practices, and the alleged shortage of seed supply and feeds. This paper reviews the state of the art of the culture of grouper, sea bass and red snapper.

Groupers (Family Serranidae) are protogynous hermaphrodites. Natural sex inversion of different species occurs at 2-11 years of age . The scarcity of wild mature males and the length of time to change sex underline the need to do induced sex inversion studies. In Epinephelus tauvina and E. fario, sex inversion was successfully induced by oral administration of 17 alpha-methyltestosterone (MT). This paper reports on the induction of sex inversion of juvenile grouper E. malabaricus using bi-weekly intramuscular injections of MT.