An ACIAR-funded project was conducted in the Rinconada Lakes area of the Bicol Region in the Philippines to improve fish cage management by fish farmers not only to improve economic returns but also to reduce the negative impact of aquaculture on the lakes’ environment The area is prone to devastating typhoons and other catastrophic events which have adversely affected the livelihood of the communities. The study consisted of stocking density and feeding trials with the cooperation of local fish farmers with the aim of shortening the culture period from the traditional 8-12 months as commonly practiced by fish farmers to enable multiple crops annually. This would enable them to harvest their stocks safely in at least one cropping prior to the advent of adverse climatic conditions. Training of the fish farmers and subsequent verification trials were also conducted as part of the study.

In the Philippines, cage culture of milkfish in marine environments is increasing. The practice uses high stocking densities, with significantly greater inputs of artificial feeds which more often than not, has led to excessive feeding and consequently excessive nutrient loading in receiving waters, exacerbating problems with pollution. These could have contributed to occurrence of periodic fish kills in areas of marine milkfish culture clusters. Sixty percent of milkfish farming expenses are attributable to feed costs. A series of experiments were conducted in an attempt to develop alternative feeding strategies that will reduce feed inputs without compromising growth and resulting production. In the first experiment, growth was compared in milkfish fed daily, on alternate days and on alternate 2-week or 4-week starvation and refeeding cycles in a tank environment provided with flow-through water system. Results show, that milkfish fed on alternate days do not grow as well as milkfish that are fed daily. Feed restriction for 2 weeks followed by 2 weeks of refeeding elicited a compensatory growth response such that average body weight (ABW) of fish was not significantly different from ABW of fish fed daily. Another experiment compared growth of fish given a ration equivalent to 10% of BW (usual practice) or 7.5% of BW. Results show no significant effect on growth or final ABW or biomass in fish fed daily or on 2-week cycles of feed restriction and refeeding. Thus, a lower feeding ration can be given to milkfish without compromising yield. Results of the tank experiments were verified in actual marine cage and brackishwater pond production systems using an initial feeding rate of 7.5% rather than 10% ABW. In the experiment in cages, survival rates between the control fish and the groups subjected to cycles of 2-week starvation followed by 2 weeks of normal feeding were comparable, except for one replicate of the starved-refed group where survival rate was very low (38.78%). After 3 cycles of starvation and refeeding, weight gain in the starved-refed groups were generally lower than in the control groups, which may suggest that small-sized fish cannot adapt very well to periodic starvation. In brackishwater ponds, growth, survival and total biomass at harvest was comparable between milkfish fed daily and those fed on alternate days. Hence, FCR was lower in the milkfish fed on alternate days compared to fish fed daily. On the other hand, survival was very low in fish subjected to 2 cycles of 2 weeks starvation followed by 4 weeks of normal feeding. These results suggest that as in tilapia, alternate day feeding can be adopted to milkfish culture in brackishwater ponds without compromising production while at the same time lowering production cost and environmental impact. Overall, these studies provide two practical strategies, reduced ration size and alternate day feeding, to improve production efficiency of milkfish, the largest finfish aquaculture industry in the Philippines.

We studied the influence of the development of aquaculture in the Philippines on the local economy, focusing on coastal fishers in two towns in Capiz and Iloilo, Panay Island, Philippines. Coastal residents in the two towns closely depend on fishing and aquaculture for both their primary and secondary incomes. The small-scale aquaculture business commenced by coastal fishermen has been expanding particularly after the 1990s. The planting of mangrove trees is promoted and small-scale aquafarming is done by coastal fishermen who exert only small environmental loads. Small-scale aquaculture, including the aquaculture of shellfish, net cage culture, pen culture, and seaweed culture, requires low initial investment and imposes minimal workload on operators in terms of breeding management up to shipment, which is why most coastal fishing people want to continue in the business. On the other hand, pond culture, practiced before the 1990s, promises no further rise in production for several reasons that include overproduction of milkfish and the outbreak of diseases in shrimp and prawn. Under these conditions, small-scale aquaculturists in two towns have established a sustainable aquaculture production system that allows them to maintain mangrove forests, utilize natural recirculation functions and help local residents obtain income.

Biophysical impacts of aquaculture, with consequences for biodiversity, vary with species and culture systems and include issues such as: nutrient enrichment/removal, chemicals, land use, species introductions, genetic flow to wild populations, disturbance of balance or introduction of pathogen/parasites, consumption of capture fishery resources, energy, and greenhouse gas emissions. Guiding principles, labeling schemes and various tools are needed to analyze performance and conformance. Ecological footprints and life-cycle analysis aim to capture biophysical performance, including up- and downstream effects of policy decisions. Aquaculture provides a range of services but also makes demands and impacts on ecosystem functions, services, and thus biodiversity.

A broad overview is given of research and information on aquaculture economics in Asia and the Pacific. Following a description of the general state of aquaculture in the region, an examination is made of the available research and information on the various aquaculture systems: inland/freshwater aquaculture; brackishwater /coastal aquaculture; and, marine aquaculture/sea farming. Studies on post-harvest handling, processing, transportation and marketing, and market analysis and development are discussed. Environmental issues and concerns, social equity and women's issues, community-based coastal resources management, technology transfer and macro-economic policies and institutional structures are also analysed. Aquaculture economics research is also assessed, highlighting thrusts, priorities, constraints and needs.

There has been little information on the importance of arachidonic acid (20:4n-6, ArA) in fish and other aquatic animals, although the importance of eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA) has been highlighted. The present study was conducted to investigate essential fatty acid composition, especially ArA distribution in mangrove organisms in the Philippines, Malaysia and Japan. The overall results revealed that ArA was not a minor component in mangrove organisms, and that the existence of ArA in mangrove organisms is widespread, irrespective of the differences in species, geography and environment. Both mangrove green and dead leaves were rich in linoleic acid (18:2n-6 LA) and linolenic acid (18:3n-3 LNA), which are respectively precursors of ArA and EPA & DHA, although ArA, EPA and DHA were not detected in these leaves. Mangrove invertebrates contained intermediate to high ArA. Especially, mangrove snails had very high ArA levels with low DHA levels, and thus the snails appeared promising as a new dietary source rich in ArA. Most of fishes in mangrove areas showed entirely higher ArA levels than EPA levels. As overall traits, ArA/EPA ratios of mangrove animals were higher than those of cold and temperate water species .The present results suggest that ArA may be nutritionally more important for egg and larval development, and that its supplementation in diets can enhance the development of broodstock management and fry production technologies in mangrove areas. The information of the present report can be used as a guideline for development of appropriate broodstock and/or larval diets in mangrove areas.

Rotifers (Brachionus sp.) were cultured with various combinations of baker’s yeast, Nannochloropsis sp., Culture selco, and DHAPS with or without supplementation of arachidonic acid (triacylglycerol form). Rotifers were able to be enriched with emulsified- arachidonic acid supplemented to culture media. Considered the reciprocal ratios of arachidonic acid, EPA and DHA in rotifers, rotifers pre-cultured in Culture selco and then cultured in DHAPS had the best balance of essential fatty acids, and the optimum level of arachidonic acid supplementation to DHAPS appeared between 0% and 5%. A feeding test was conducted to investigate the effects of arachidonic acid on the broodstock performance of rabbitfish (Siganus guttatus), one of the commercially valuable species in mangrove areas. A diet with 1.5% of arachidonic acid supplementation appeared to affect negatively the reproductive performance of S. guttatus broodstock, perhaps due to the excessive supplementation. Considered together with results of mangrove red snapper in 2003, the optimum supplementation of arachidonic acid in broodstock diets might be around 0.5%.

In 1977, scientists at the Southeast Asian Fisheries Development Centre (SEAFDEC) in the Philippines became the first anywhere to succeed in breeding milkfish (Chanos chanos) in captivity. The advance was made possible by an IDRC grant, approved in 1974, for a three-year project of research in the breeding and rearing of this important source of protein. The initial grant, for $826,000, was renewed for another three years in December 1978 in the amount of $421,100.