Southeast Asia has the highest concentration of mangroves and brackish water aquaculture ponds. This paper describes studies that integrate mangroves as biofilters, and as pen culture sites for mud crab farming. In one study, passing shrimp pond effluents through a natural mangrove stand reduced levels of TSS, sulfide, NH₃-N and NO₃-N by 18.7%–64.2%. Estimates show that 1.4–6.5 ha of mangroves are needed to assimilate nitrogen wastes from one hectare of shrimp pond. Mangrove biomass increase was 2.5 times greater with effluents compared to a control mangrove, although plant numbers remained similar. Present mud crab Scylla spp. farming still depends on raw (“trash”) fish and wild seed. To lessen such dependence, another study compared the stocking of hatchery vs wild juveniles, and feeding of pellet + raw fish (“trash fish”) vs fish alone. Preliminary results show that low-cost pellets can reduce raw fish requirement, and that hatchery crab juveniles need immediate feeding whereas wild crabs can subsist on natural mangrove productivity for one month. Mud crab pen culture is commercially viable but technological refinements and land tenure issues remain.

The petrochemicals produced from refining oil have become a large part of human life, making oil a valuable and expensive commodity. As a non-renewable resource, extraction and transport efforts have intensified to keep up with the demand, increasing the occurrences of oil spills. Such accidents have devastating impacts on the environment, the health of organisms, and a country's economy like the Philippines, and thus, need to be resolved immediately. One way to deal with oil spills is through bioremediation but the process is still facing several challenges. For one, the toolbox for bioremediation is limited. About 79 genera of bacteria were observed to degrade oil but there are only a small number of bacterial species and/or strains that have been recognized as useful for bioremediation. Second is that most oil-degrading bacteria found have low oil degradation efficiencies. Another challenge is keeping the bacteria alive to carry out the process. Fortunately, progress has been made in solving these challenges. Researchers are now testing different consortia, including bacteria–bacteria, bacteria–fungi, bacteria–microalgae, that can complement each other such as biosurfactant-producing bacteria with different oil-degrading microorganisms or microalgae or fungi that enhance the growth of oil-degrading bacteria. A consortium like this improves the survivability of each microorganism and enhances the oil-degrading efficiency. Moreover, the search for additional oil-degrading and biosurfactant-producing bacteria and other microorganisms to add to the bioremediation toolbox has been improved with the emergence of high-throughput sequencing. Aside from microorganisms, seaweeds have shown potential for bioremediation. The seaweed Caulerpa prolifera has been demonstrated to degrade diesel up to a certain concentration with the help of the bacteria growing on its surface. Bioremediation has a long way to go, but recent developments have shown promise and it remains to be the cheapest, most environment-friendly, and most effective way of dealing with oil spills.

The relationship between virulence and overall within-host fitness of the fish rhabdovirus Infectious hematopoietic necrosis virus (IHNV) was empirically investigated in vivo for two virus isolates belonging to different IHNV genogroups that exhibit opposing host-specific virulence. U group isolates are more virulent in sockeye salmon and M group isolates are more virulent in rainbow trout. In both single and mixed infections in the two fish hosts, the more virulent IHNV type exhibited higher prevalence and higher viral load than the less virulent type. Thus, a positive correlation was observed between higher in vivo fitness and higher host-specific virulence in sockeye salmon and rainbow trout. Comparisons of mean viral loads in single and mixed infections revealed no evidence for limitation due to competition effects between U and M viruses in either rainbow trout or sockeye salmon co-infections.

In milkfish farming, when food wastage is high and assimilation is poor, most of the nutrients added to the culture species may ultimately pollute the environment. Assessment of water dispersion from ponds and cages rarely take into account the physical properties of feeds. This study dealt with settling velocity, physical stability, and the amount of nutrients (nitrogen and phosphorus) generated by milkfish feeds alone in water. Four locally manufactured milkfish (Chanos chanos) pelleted feeds labeled as: Grower A, Grower B, Grower C, and Finisher D were tested, with freshwater, brackishwater and seawater as test media. Settling velocities of the four feeds were generally greater in freshwater than in brackishwater and in seawater, ranging from 11.0-11.5 cm s^-1 for 6-8. mm long pellets, and 12.8.0-13.0 cm s^-1 for 9-11 mm pellets with Milkfish Finisher D. In brackishwater, settling velocities of size ranges 6-8 and 9-11 mm long were 9.8-10.0 and 11.0-11.6 cm s^-1 respectively. In seawater, settling rates of milkfish feeds were 8.0-8.5 and 9.8-10.1 cm s-1, for the same size ranges. There was no significant difference on the settling velocities among feed brands tested but significantly different within water types (P> 0.05). Water stability of these pellets was tested within 15, 30, 60 and 120 minutes immersion time. The four-feeds tested showed a range of water stability of 84.4-87% for the first 15 min in seawater, 70-82 % in brackishwater and 74-82% in freshwater. They are not that water stable after one hour with water stability of 35-40%. Nutrient contribution assessment of these feeds was also carried out by submersion test. Total ammonia nitrogen (TAN) concentrations in freshwater generated by the four feeds were low and were not that significant during the first two days. Values abruptly rose above the initial concentrations of 0.04 to 3.25-6.97 mg l^-1 on the6th day of submersion. In freshwater, Grower A had the highest TAN concentration value of 6.97 mg l^-1 and Grower D had the lowest value of 0.1 mg l-1. Nitrite concentration was low at a range of 0.01-0.04 mg l^-1 while nitrate ranged from 0.1-0.76 mg l^-1 for all the feeds. In brackishwater, TAN concentrations steadily rose to a range of 2.5-3.5 mg l^-1 in all feeds, while in seawater a lower concentration than the brackishwater of 0-1.2 mg l^-1 within 7 days of submersion was obtained. Phosphate-P concentrations rose on the second day of submersion in all test media and abruptly fell on the fifth day. Grower B gave the highest phosphate concentration of 1.55 mg l^-1 in freshwater and 1.44 mg l^-1 in brackishwater by the same feed and 2.0 mg l^-1 by Grower A in seawater. ANOVA showed no significant differences among the feeds in terms of N and P concentrations obtained within seven days of submersion (P< 0.05). Nutrient inputs from feed undergo nutrient transformation and nutrient buildup was very apparent especially in freshwater and in brackishwater. The results of this study are measures of the significance of physical properties and nutrient releases of commercial feeds on the water quality of milkfish culture system. Data gathered can be applied into feeding management techniques, selection of good quality feeds and can be incorporated into models defining the impact of pollution from commercial feeds on the environment.

The onset of digestive enzymes in the various regions of the digestive tract of sea bass, Lates calcarifer (Bloch) at days 0. 2, 5, 10, 20, 30, and 40 after hatching was investigated. This study aims to correlate which enzymes are detectable in stated regions of the developing gut and to relate this pattern to the feeding habit of sea bass. Alkaline phosphatase and esterase were localized in the intestine of the 2 day old larvae. At 5 days post-hatching, esterase was present in the esophagus. At the beginning of metamorphosis (20-days post-hatching), alkaline phosphatase, esterase, and amino peptidase were localized in the pyloric caeca. Aminopeptidase's and lipase were observed in the brush border of the intestinal epithelial cells. At the end of metamorphosis (30-days-post-hatching), all enzymes investigated in this study were present. Esterase was demonstrated in the columnar cells of the stomach while lipase and amylase were observed in both columnar cells and gastric glands. Protease and amylase were present in the pyloric caeca and intestine. During the early juvenile stage (40-days-post-hatching), esterase was localized in the gastric glands of the stomach. The appearance of esterase activity as early as day 2 was correlated with endogenous to zooplanktivorous feeding. In the same manner, the presence of aminopeptidase's, lipase, protease, and amylase at day 20 to 30 onwards was related to a change in feeding habit of sea bass from zooplanktivorous to real carnivorous. The findings of this study demonstrate the need for basic studies for feed formulation and management of the fish.

Combining feeding appendage morphology and behavioural observation of the motion pattern of the feeding appendages clarified many aspects underlying the feeding processes of the giant freshwater prawn (Macrobrachium rosenbergii) and the marine whiteleg shrimp (Litopenaeus vannamei) in aquaria. The food intake behaviour was video recorded during eating pellet food, pieces of fresh squid and fish. While M. rosenbergii took pellet one by one, L. vannamei picked up many pellets at one time and held them at the mouth with the 3rd maxilliped endopods and the 1st walking legs. Both species used the right chelate walking legs rather than the left walking legs to pick up the food. The 3rd walking legs of L. vannamei were longest and heaviest among the chelate walking legs but their major role was not for feeding but for feeding contests aggression. While M. rosenbergii easily crunched pellets by the mandibles, L. vannamei did not crunch pellets due to the softer and not strong mandibles and frequently spat out them, indicating that the present hard pellets are not suitable for L. vannamei. Both species kept a piece of elastic fresh squid or fish flesh at the mouth and tore the food into small pieces with the help of repeated pulling down motion of the 3rd maxilliped endopods. However, the mandible teeth of the two spices were not sharp enough to gnaw off the fibrous muscle in one bite. The 2nd and 3rd maxilliped endopods were used for holding food at the mouth and did not contribute to mastication of food. The 2nd and 3rd maxilliped exopods exhibited the horizontal fanning motion, which a unidirectional water flow moving backwards in the gill chamber (visualized with milk). The maxilliped exopods were found to contribute not to feeding but ventilation. Based on the results obtained, development of softer pellets was recommended for L. vannamei.

Among farm inputs, feeds are the highest recurring cost in aquaculture. Indeed, feeds have become even more expensive after the COVID-19 pandemic, undeniably affecting the aquaculture economics. The pressing need to alleviate feed costs has to be prioritized, considering its implications for sustained aquaculture production to support the ever-increasing global population. Substantially, the rising costs of manufactured feeds have driven the continuous quest for new alternative feed ingredients in aquafeeds and the adoption of feed management strategies to improve the profitability of aquaculture operations. These two strategies addressed in this study are imperative in promoting freshwater aquaculture among the ASEAN Member States. This article highlights the exploration of feeding trials using alternative protein sources and feeding strategies. Because of their economic relevance to the freshwater aquaculture industry in the Philippines, Nile tilapia, giant freshwater prawn, and tropical anguillid eel, particularly the Pacific shortfin eel, were chosen in this study.