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.

This technology search was funded by the Global Technology Search (GTS) Program of the Department of Science and Technology (DOST) through the Technology Application and Promotion Institute (TAPI) upon recommendation and endorsement of the Philippine Council for Aquatic and Marine Research and Development (PCAMRD). The program expands the research and development (R&D) arena outside the country. Through a well-planned and thoroughly developed scheme, appropriate technologies are obtained from outside sources to shorten the R&D process and keep the country abreast on the most recent developments in science and technology (S&T). The search for technologies on sustainable shrimp culture in ponds was successfully undertaken in Thailand by the authors during the period 02-15 September 1997. Travel arrangements and funding were arranged by sponsoring agency. Researchers from the Thai National Institute of Coastal Aquaculture (NICA) and the Aquatic Animal Health Research Institute (AAHRI), who were responsible for sustainable shrimp culture in Thailand guided us in our search. Information were gathered from small- medium- and large-scale shrimp farming operators in south, central and east Thailand.

Milkfish (Chanos chanos) fingerlings with an average weight of 16.3 g were stocked at 4000 per ha in twelve 500-m² experimental brackishwater ponds. The duration of supplementary feeding using pelletized chick starter (21.15% protein) at a ration of 5% of the biomass, was varied between 0 and 3 months. The duration of supplementary feeding had no significant effect on the survival, growth and production of milkfish. The results indicated that supplementary feeding of milkfish was not necessary at a stocking level of 4000 fish/ha, when adequate pond fertilization was carried out.

This study examined the effect of stocking density on growth, biochemical composition, and blood parameters of the Pacific shortfin eel Anguilla bicolor pacifica. Elvers (1.95 ± 0.14 g body weight) were randomly stocked in indoor tanks and reared over 186 d at three stocking densities (0.3, 0.6, and 0.9 kg m^-3) set up in triplicates. Except for survival and biometric indices, elvers maintained at 0.3 and 0.6 kg m^-3 densities exhibited higher growth and feed utilization than those held at 0.9 kg m^-3. Yield increased with stocking density, which were significantly higher at 0.6 and 0.9 kg m^-3. RNA/DNA ratio did not reflect growth rate, but trends in survival and RNA/DNA ratio with stocking density were positively related. In contrast to body proximate composition, increasing stocking density resulted in significantly higher erucic acid (22:1n-9) and total saturated fatty acid levels at 0.6 and 0.9 kg m^-3 densities, respectively. Serum glutamic pyruvic transaminase activity was significantly elevated at 0.6 kg m^-3, while total protein, glucose, and triglycerides slightly decreased with increasing stocking density. Results suggest that Pacific shortfin eel elvers can be reared in indoor tanks at a stocking density of 0.3 – 0.6 kg m^-3 to achieve acceptable growth, feed performance, and health condition.

The Philippines remains one of the top eucheumatoid seaweed producers worldwide. However, the reported seaweed health problems affecting farms have been one of the reasons for the decline in seaweed production in the country. Outbreaks of “ice-ice” disease (IID), epiphytic pests, and grazing problems have significantly reduced biomass yields and compromised carrageenan quality, directly affecting the livelihood of tens of thousands of families dependent on seaweed farming. In this chapter, we listed seaweed health problems based on type-association with the host seaweed plant and highlighted factors contributing to farm problems. Additionally, recommendations are presented that are relevant to the protection of the long-term sustainability of the eucheumatoid seaweed farming industry in the Philippines.

Freshwater prawns of the genus Macrobrachium are among the most valuable cultured aquatic species in the world. The systematic study of Macrobrachium species in the Philippines has often been based on morphological trait assessment. Here, we combined morphology and molecular approaches to study the presence and actual distribution of Macrobrachium species along the Cairawan River in Laua-an, Antique Province, Panay Island. Using morphological characteristics, we identified 11 Macrobrachium species, the highest number of species reported from a single river. Molecular results based on the cytochrome oxidase subunit I (COI) mitochondrial DNA (mtDNA) sequences confirmed the morphological identification. The analysis revealed eight major clades with 19 distinct haplotypes within the species. Our results provide information on the identification of Macrobrachium species inhabiting the Cairawan River. The baseline information can be helpful for future genetic studies involving freshwater prawns with potential use in aquaculture. It can provide scientific data to facilitate the formulation of selective breeding plans and direct governance policies in freshwater prawn resource conservation and management in the Philippines.

Understanding the genetic diversity and population structure of anguillid eels is crucial for effective management. In this study, we used the mitochondrial DNA (mtDNA) D-loop marker to identify anguillid glass eels and assessed their genetic diversity across six sampling sites spanning three Southeast Asian countries. We also examined the population structures of Anguilla marmorata and A. celebesensis. We validated nine distinct species and subspecies of anguillid eels from 465 specimens collected in Indonesia (n = 246), the Philippines (n = 119), and Vietnam (n = 100). High gene diversities were observed across the species, ranging from 0.979 (A. celebesensis) to 1.000 (A. bicolor bicolor, A. marmorata, and A. interioris). Correspondingly, nucleotide diversity values were relatively low, varying from 0.036 (A. marmorata) to 0.057 (A. interioris). A. marmorata (n = 162) displayed a broad distribution, being observed across all six sites, with a significant yet low average fixation index of 0.05755. Pairwise comparisons of FST values between Cimandiri and other locations (except for Cagayan) were relatively high and statistically significant (p < 0.01), indicating significant genetic differentiation of Cimandiri samples compared to most locations in this study. On the other hand, A. celebesensis (n = 110), exhibited a non-significant and low fixation index (0.007), indicating no genetic differentiation in samples from Poso and Poigar Rivers, Indonesia. Our findings highlight the essential need for coordinated management strategies among regions that share common stocks. Additionally, this study underscores the efficacy of the mtDNA D-loop in precisely identifying glass eel species/subspecies and elucidating the genetic diversity and population structure of tropical anguillid eels.

The sandfish Holothuria (Metriatyla) scabra, is a high-value tropical sea cucumber harvested from wild stocks for over four centuries in multi-species fisheries across its Indo-Pacific distribution, for the global bêche-de-mer (BDM) trade. Within Southeast Asia, the Philippines is an important centre of the BDM trade, however overharvesting and largely open fishery management have resulted in declining catch volumes. Sandfish mariculture has been developed to supplement BDM supply and assist restocking efforts; however, it is heavily reliant on wild populations for broodstock supply. Consequently, to inform fishery, mariculture, germplasm and translocation management policies for both wild and captive resources, a high-resolution genomic audit of 16 wild sandfish populations was conducted, employing a proven genotyping-by-sequencing approach for this species (DArTseq). Genomic data (8,266 selectively-neutral and 117 putatively-adaptive SNPs) were used to assess fine-scale genetic structure, diversity, relatedness, population connectivity and local adaptation at both broad (biogeographic region) and local (within-biogeographic region) scales. An independent hydrodynamic particle dispersal model was also used to assess population connectivity. The overall pattern of population differentiation at the country level for H. scabra in the Philippines is complex, with nine genetic stocks and respective management units delineated across 5 biogeographic regions: (1) Celebes Sea, (2) North and (3) South Philippine Seas, (4) South China and Internal Seas and (5) Sulu Sea. Genetic connectivity is highest within proximate marine biogeographic regions (mean F_st=0.016), with greater separation evident between geographically distant sites (F_st range=0.041–0.045). Signatures of local adaptation were detected among six biogeographic regions, with genetic bottlenecks at 5 sites, particularly within historically heavily-exploited locations in the western and central Philippines. Genetic structure is influenced by geographic distance, larval dispersal capacity, species-specific larval development and settlement attributes, variable ocean current-mediated gene flow, source and sink location geography and habitat heterogeneity across the archipelago. Data reported here will inform accurate and sustainable fishery regulation, conservation of genetic diversity, direct broodstock sourcing for mariculture and guide restocking interventions across the Philippines.