From 2008 to 2014, we monitored the abundance and daytime habitat use of the freshwater shrimp Macrobrachium yui at a fixed site on a tributary of the Xuang River in northern Laos. Throughout the monitoring period, the shrimp M. yui showed strong preference for cobble and small boulder substrates, as well as moderate preferences for 21–30 cm depth and the midstream (251–350 cm distance from the bank) as daytime habitat factors. The shrimp M. yui, on the other hand, exhibited intense avoidance for shallower water depths (less than 10 cm), stagnant (0 cm s⁻¹) and faster water velocity (greater than 60 cm s⁻¹), finer substrates (from silt to gravel), and stream margin (less than 50 cm from the bank). During the day, the habitat with the cobble and small boulder in the midstream is probably the best place for the shrimp M. yui to hide from predators. The abundance of the shrimp M. yui had positive and negative correlations with water depth and sand percentage in the bottom sediment, respectively. It suggests that a decrease in water depth caused by increased deposition of fine sediment from the catchment has a negative impact on the shrimp abundance.

This study examined the performance and suitability of two tropical anguillid eels, Anguilla bicolor pacifica and A. marmorata, under cage culture conditions. Juvenile eels (1.73 ± 0.14 g body weight) of each species were stocked in triplicate hapa net cages (1 × 1 × 1.5 m; 30 eels/cage) suspended in outdoor tanks. Growth, feed utilization, biochemical composition and blood chemistry of the two species were compared after 210 days. Except for survival, mean final body weight (FBW), weight gain percentage (WG), specific growth rate (SGR) and yield of A. bicolor pacifica (64.51 ± 13.07 g, 3514 ± 690%, 2.14 ± 0.12%/day, 1534 ± 380 g/m³) were significantly higher than that of A. marmorata (7.77 ± 2.90 g, 356 ± 125%, 0.89 ± 0.16%/day, 178 ± 89 g/m³). In comparison with A. bicolor pacifica, significantly lower feed intake (FI), feed efficiency (FE) and protein efficiency ratio (PER) observed in A. marmorata suggest the need to develop eel diets with feeding stimulants to improve feed acceptance. Biometric indices, body proximate and amino acid composition were not significantly different between the two species. However, serum glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT) and total protein (TP) in A. bicolor pacifica were significantly higher than that in A. marmorata. These findings suggest that the differences in growth performance and feed utilization between the two anguillid eel species are related to feed palatability, and that A. bicolor pacifica appears to be a suitable species for cage culture because of its faster growth.

The nearshore (Soya Warm Water (SWW)) and offshore (Intermediate Cold Water (ICW) and Okhostk Sea Low Salinity Water (OSLSW)) waters in the Okhotsk Sea differ substantially in their physico-chemical characteristics. Thus, the extent to which water mass mixing impacts phytoplankton dynamics in the Japanese scallop Patinopecten yessoensis culture areas needs to be assessed to properly manage scallop stocks. This study examined the phytoplankton dynamics in nearshore (SWW) and offshore (ICW and OSLSW) waters and phytoplankton response to water mass mixing (SWW + ICW, OSLSW + ICW) for 5 days in spring (2007) and summer (2007–2009) microcosm experiments. Increased chlorophyll a concentration in ICW was observed due to higher nutrients available for phytoplankton uptake than in OSLSW and SWW at the start of each microcosm experiment. In comparison to spring microcosm, mixing of SWW + ICW promoted higher chlorophyll a concentration and faster Si(OH)₄ utilization than in OSLSW + ICW in summer. In addition, the size structure of chlorophyll a differed from micro-size (>) in SWW + ICW to nano-size (<) chlorophyll a in OSLSW + ICW. Suspended particulate organic matter (SPOM) \(\mathsf{\delta^{13}C}\) ratios were positively correlated with chlorophyll a in both mixed microcosms whereas SPOM \(\mathsf{\delta^{15}N}\) isotopic ratios were inversely related to nitrate concentration in SWW + ICW, except in spring. This suggests that stable isotopes can be used in predicting phytoplankton biomass and nutrient utilization. In comparison to microcosm experiments, nearshore water column structure suggests vertical water mixing in summer to autumn when phytoplankton biomass and micro-size fraction were at maximum. Taken together, the advance of nutrient-rich ICW to nutrient-poor nearshore areas in the Okhotsk Sea resulted in increased chlorophyll a biomass and dominance of micro-size phytoplankton in summer, potentially enhancing nutrient and food supply to bottom-cultured scallops as suggested by both microcosm experiments and field observations.

Polychaete is considered the best maturation diet for penaeids; however, fluctuating supply and quality warrant detailed studies to understand the specific maturation-promoting factors present in polychaete. Indian white prawn, Penaeus indicus, was fed diets supplemented with different fractions of Marphysa sp. extracts. Fractions, such as the total soluble fraction (TSF), neutral lipid fraction (NLF), and polar lipid fraction (PLF), were incorporated in the maturation diet at 0.25, 0.50, and 1.00% following a 3 × 3 factorial design. One group was fed with basal diet (BD), and another was fed with fresh squid, mussel, and polychaete, serving as the control. After a 30-day feeding trial, results showed that the inclusion of polychaete extracts in the diet significantly improved P. indicus maturation compared to groups fed BD and control with 40% maturation rates (MR) (p = 3.4 × 10⁻⁴). MR was optimum in groups receiving diets supplemented with ≥0.5% TSF (70.00% ± 0.00) and NLF (60.00% ± 5.77). Similar improved MR was achieved in treatments receiving ≥0.25% PLF supplementation (60% ± 0.00). Accordingly, relative expression of ovarian vitellogenin mRNA of broodstock fed under 0.25 and 0.50% PLF group was 4.44 and 3.96 folds higher than BD, respectively (p = 0.003). No significant differences were detected in the broodstock survival, latency period, hepatosomatic, and gonadosomatic indices. Biochemical content analyses showed no significant differences among the nine treatments except for broodstock's higher ovary protein content in the TSF group (p = 0.037). This study highlights PLF as the most potent component of the polychaete extract in promoting gonad maturation in P. indicus maturation supplemented at a 0.25% optimum inclusion level.

One dilemma facing the farming of the carrageenophyte Kappaphycus is the deteriorating quality of seedstock. Rejuvenating the commercial stocks using spores from reproductive wild parents that are sexually and asexually produced could perhaps restore the traits that are useful for culture. The use of gametophyte and sporophyte (=tetrasporophyte) phases of Kappaphycus alvarezii from spores is explored as a source of seedstock. The growth and physical properties of semi-refined carrageenan extracted from the resulting sporophyte and gametophyte thalli of the same ages were determined. The growth rate of the diploid tetrasporophyte thalli was significantly higher than that of the haploid gametophyte. Gel strength and yield of semi-refined carrageenan from the two life cycle phases were not significantly different, whereas the viscosity was significantly higher in the diploid tissues. Kappaphycus sporophytes were potentially superior to gametophytes as a source of seedstock for mariculture, but problems need to be addressed – including improving the growth rate and reducing the cost of production – before its application could be realized.

This study evaluated the suitability of five diatom species (Amphora sp., Cocconeis sp., Navicula ramosissima, Nitzschia sp., and Tryblionella sp.) as food to abalone Haliotis asinina early juveniles (5-mm shell length). Grazing periodicity, grazing rate, and feeding preference were measured; at the same time, abalone gut content was examined. Grazing incidence appeared to be continuous with significantly higher grazing intensity observed at nighttime from 6 p.m. to 10 p.m. (79%) than at daytime from 10 a.m. to 2 p.m. (40%) (p < 0.05). Grazing rates from 6 p.m. to 10 p.m. were significantly higher on N. ramosissima (1.6 × 105) among diatom species but was not statistically different from Cocconeis sp. (1.1 × 105) (p > 0.05). Broken cells of Amphora sp. (22%) were significantly higher in the gut of H. asinina compared to Cocconeis sp. (2.8%), N. ramosissima, (1.8%), and Tryblionella sp. (0.2%) although the abundance of Nitzschia sp. (6%) was not significantly different from Amphora sp. (p > 0.05). Early juveniles showed significant preference for Cocconeis sp. (18.6%), followed by Nitzschia sp. (16.2%), N. ramosissima (13.9%), and Amphora sp. (13.4%), with the least preference for Tryblionella sp. (7.8%). Survival of H. asinina was similar in 4 diatom species (46–71%) except in Tryblionella sp. (8–12%). These findings suggest that diatom species Cocconeis sp., Nitzschia sp., Amphora sp., and N. ramosissima are the suitable live food for H. asinina early juveniles. Knowledge from this study would contribute to the development of a feeding protocol that would maximize production of H. asinina early juveniles in the hatchery.

The settlement of sea cucumbers is a crucial phase of larval development because the highest mortality occurs at this stage. Substrates and cues are commonly used to induce larval settlement. Commercial algae and live benthic diatoms are the most common settlement cues being used. The present study evaluated Chaetoceros calcitrans concentrate as a potential settlement cue for H. scabra. Three settlement cues, replicated three times, were compared: commercial ‘Spirulina’, live benthic diatom Navicula sp., and C. calcitrans concentrate. Settlement substrates without cue served as control. ‘Spirulina’ paste and C. calcitrans concentrate were painted onto the settlement substrates, while settlement substrates were introduced into a Navicula sp. culture tank to enable attachment of the benthic diatom. Faster and higher settlement was observed in the treatment with ‘Spirulina’ paste as cue at 89% five days post introduction of substrates, compared with live Navicula sp. and C. calcitrans concentrate at 74% and 63% seven days post introduction, respectively. For the control, only 25% of the larvae have settled eight days after introduction to the substrates. ‘Spirulina’ paste and live Navicula sp. showed better settlement rates, but these were not significantly different compared with C. calcitrans concentrate. Therefore, C. calcitrans concentrate can be a potential settlement cue for H. scabra larvae.

The increasing global population resulted in intense pressure on the food production sectors to meet the rise in food demand. The aquaculture industry, which is one of the major food production sectors, provides opportunities in addressing issues on malnutrition and poverty alleviation. Shrimp farming is an important sub-sector in aquaculture because shrimp are not only good sources of food, but they contribute to the national economy through export revenues. This resulted in the rapid intensification of shrimp aquaculture, which created negative issues on sustainability and environmental impacts. Hence, this necessitates an urgent need to develop aquaculture production systems that yield high productivity and profitability yet possess a low carbon footprint. Biofloc technology (BFT) fit into these criteria as this technology permits intensive culture of aquatic species, less use of resources, and improved water quality as a consequence of the production and activity of beneficial microbial biomass, which, at the same time, can be utilized as a source of feed for the growing shrimp. BFT has been shown to be successful on a commercial scale during shrimp grow-out, and recent studies have shown that this technology can be further refined and optimized for the production of shrimp during the nursery phase. This review, therefore, highlights the basics of BFT and how this technology is being optimized in the production of shrimp during the nursery phase. More specifically, this discusses the benefits of this approach in ensuring a productive yet sustainable way of producing shrimp in the context of Philippine aquaculture.

This study aimed to expand current knowledge on TiLV genetic diversity by sequence analysis of a portion of genome segment 3 of TiLV detected from the Philippines. This includes a recently deposited sequence in GenBank (Accession No. LC504279) and six new sequences from cases of infection reported from 2017 to 2020. Phylogenetic analysis of 179 bp fragment of segment 3 showed that the seven TiLV isolates from the Philippines can be divided into three phylogenetic groups. When comparing all sequences, unique nucleotide substitutions and amino acids were noted among these groups. Variation in mortality rates in naturally infected samples was also observed; however, poor environmental conditions during the disease outbreak may also contribute to the mortalities. These suggest the presence of at least three phylogenetic groups of TiLV in the Philippines which has significant implications for the future development of a vaccine, diagnostic kits, and genetic selection programs.

We verified the efficiency of poultry by-product meal (PBM) as a substitute for fish meal (FM) in feed for juvenile milkfish (Chanos chanos). Juveniles (mean 48.0 g) were fed for 12 weeks with two experimental feeds containing different levels of PBM (8.0% and 12%), FM (10% and 5.0%), and cod liver oil (fish oil or FO, 4.0% and 3.8%). A feed without PBM having higher levels of FM and FO (20% and 4.5%, respectively) was used as control. Weight gain, specific growth rate, and feed conversion ratio were not significantly affected by the levels of dietary PBM. In addition, no significant differences were detected among the dietary groups in plasma triglyceride, total cholesterol, phospholipid, glucose, or total protein concentrations. Furthermore, crude protein, crude fat, moisture, and ash contents in the whole body, liver, and dorsal muscle were not significantly influenced by the dietary treatments. The results of organoleptic examinations that included tests of smell, flavor, and texture were almost the same among the dietary groups. These results indicated that PBM is the applicable substitute for FM, with performance of the high PBM feed (PBM-FM-FO = 12%-5.0%-3.8%) being comparable to that of the control feed.