A 60-day feeding trial was conducted to evaluate the effect of inclusion frequency of hatchery-bred mud polychaete, Marphysa iloiloensis, as part of a combination diet on the reproductive performance and larval quality of domesticated P. indicus. The two treatments were fed with a combination of formulated diet, mussel, squid, and mud polychaete with once (T1) and twice (T2) a week inclusion in the feeding regime. In contrast, the control group was fed only a diet combination of mussels, squid, and formulated diet. There was no significant difference in the mean survival of male and female broodstock in all treatments upon termination (\(p\gt0.05)\). Shrimp in T1 and T2 performed significantly better than the control in terms of spawning frequency (\(p=0.037)\) and fertilization rate (\(p=0.001)\), while T1 had significantly high re-maturation (\(p=0.038)\). The survival, spawning, hatching rate, egg, and nauplii production did not differ significantly among treatments (\(p\gt0.05)\). Also, no difference in the gonado-somatic index (GSI), hepato-somatic index (HSI), spermatophore weight, and sperm count was found among diet treatments (\(p\gt0.05)\). Post larvae from T1 and T2 performed significantly better than the control after 25 (\(p=0.008)\) and 30 (\(p=0.009)\) minutes of abrupt exposure to freshwater, respectively. Therefore, even once weekly, mud polychaete inclusion is sufficient to improve the reproductive performance of P. indicus broodstock and produce offspring with boosted resistance in the hatchery.

Nursery systems are valuable production tools in shrimp aquaculture and are effective biosecurity facilities for the high-density culture of shrimp postlarvae (PL), resulting in healthy and uniform-sized juveniles. The nursery production of shrimp is usually carried out in small ponds; however, the use of small and circular tanks with plastic liners is gaining popularity. From an industry standpoint, there is a need to assess how nursery systems can improve the productivity of the shrimp production cycle. Hence, the use of small circular tanks coupled with the incorporation of biofloc technology was assessed in terms of its viability during the nursery production of the Pacific whiteleg shrimp, Litopenaeus vannamei. A 450m² plastic-lined circular tank was installed and prepared for the stocking of L. vannamei postlarvae (PLs) at a density of 500 PLs per m². Biofloc was produced and maintained throughout the nursery phase by adding brown sugar as a carbon source at carbon to nitrogen (C:N) ratio of 10. Daily monitoring of the various water quality parameters was carried out, while presumptive Vibrios were enumerated weekly. The shrimp juveniles were sampled for their body weight on the 14th day post-stocking and weekly until harvest on the 30th day of culture. The different water quality parameters were within optimum levels required for shrimp growth. Presumptive Vibrios were dominated by the yellow colonies. The shrimp attained 100% survival with an average body weight of 1.26 g and a feed conversion ratio (FCR) of 0.43 at the end of the nursery production phase. Our results indicate that the use of small circular tanks with biofloc during the nursery production phase of whiteleg shrimp is feasible and can be incorporated during the grow-out culture for improved and continuous production of this shrimp species.

Eucheumatoids are the major seaweed species cultivated in most coastal areas in the Philippines, being a major source of income for many families. Seaweed farmers face issues such as lack of good quality cultivars and the presence of diseases and epiphytes in the cultivated stocks. This study characterizes the wild eucheumatoids, which are potential sources of cultivars that might be resistant to diseases and epiphytes. Wild eucheumatoids were collected from Iloilo (N=18), Guimaras (N=10), and Bohol (N=20), Philippines. Gross morphology was described, and a 10-mm apical tip was excised for DNA extraction. PCR amplification and sequencing using cox2-3 spacer genetic markers were done. Based on sequence data, 5 species can be identified from the Visayas region: the commercially cultivated Kappaphycus alvarezii (Iloilo, Bohol), K. striatus (Iloilo, Guimaras), and Eucheuma denticulatum (Iloilo, Bohol) and the currently uncultivated K. cottonii (Iloilo) and Kappaphycus sp. (Iloilo, Bohol). Haplotype network analysis identifies individuals of K alvarezii and E. denticulatum as haplotype E3 and E13, respectively, which are haplotypes previously reported from seaweed farms and globally distributed for cultivation purposes. The K. striatus from Iloilo and Guimaras are identified as haplotype E89, and the K. cottonii from Iloilo is haplotype E108 which has been described previously from seaweed farms and wild populations, respectively. Interestingly, Kappaphycus sp. from Iloilo and Bohol are identified as haplotype GUI1 initially described in 2014 and yet to be identified up to the species level. Our study shows that purely morphological identification is not sufficient to reliably identify species, thus highlighting the need to employ molecular techniques supporting strain selection. In summary, it reveals a rich diversity of wild eucheumatoids in the Visayas region of the Philippines. In-vitro studies need to reveal the performance of individuals from these wild populations but highlight a great potential for the development of new cultivars.

Eel aquaculture is an important activity in Southeast Asian countries such as Indonesia, Philippines, and Viet Nam. With the decline in the wild fishery stock of cold-water eel species (European eel Anguilla anguilla, Japanese eel A. japonica, and American eel A. rostrata (Tatsukawa, 2003; Gómez-Limia et al., 2022), there has been an increasing interest in the culture of tropical eel species as an export commodity. In the Philippines, species of anguillid eels cultured are mainly the Pacific shortfin eel A. bicolor pacifica and the giant mottled eel A. marmorata. Anguilla bicolor pacifica is now being considered as an alternative to A. japonica (Muthmainnah et al., 2016), being the most preferred eel species for consumption in East Asian countries. However, A. marmorata, which comprised the bulk of the wild glass eel catch in the Cagayan River, Philippines, has rarely been cultured as an export commodity. Comparison of performance and feed utilization may provide relevant information on the culture requirements of these two eel species under cage conditions.

This manual describes the various methods for culturing microalgae and other natural food organisms fed to freshwater fish/prawn larvae that are produced and reared in hatcheries. Hence, it will encourage/ promote the use of natural food organisms be these live and/or processed (concentrated algal pastes), as a means of optimizing larval fish/prawn production. The manual was written purposely for local freshwater fish/prawn hatchery owners/operators and their technicians. The authors prepared the manual for hatchery operators to have a better understanding of how and why there is a need to culture natural food organisms as part of the standard larval rearing protocol and to increase/boost fish and/or prawn seedstock production.

This study examined the effects of feeding fermented tuna by-product (FTBP) on the growth, non-specific immune response, liver and intestinal morphology, and disease resistance of olive flounder Paralichthys olivaceus. Olive flounders (n = 20; 2 g) were randomly assigned into four dietary groups in triplicates. Fish were fed four test diets (50% crude protein; 10% crude lipid) for 10 weeks in which unprocessed tuna by-product (TBP) meal was replaced (on a protein basis) with 0% (FTBP0 as the control diet), 15% (FTBP15), 30% (FTBP30), and 60% (FTBP60) of FTBP protein. Results showed that growth performance, blood parameters, and proximate composition were not influenced by FTBP inclusion. Non-specific immune parameters such as superoxide dismutase activity in the FTBP30 and FTBP60 groups were significantly higher than in the FTBP15 and the control groups, whereas lysozyme and myeloperoxidase activities were not different. Liver histopathology revealed normal architecture in groups fed FTBP0 and FTBP15 diets although mild alterations were noted in the FTBP30- and FTBP60-fed groups. Intestinal villi height and muscular thickness were not significantly altered with FTBP inclusion. Moreover, higher cumulative survival rate was observed in the FTBP60-fed group than fish fed with the other diets following the 13-day challenge with E. tarda. Together, these results demonstrate that fermented tuna by-product meal could be included at 60% in olive flounder diets.

An innovative microalgae harvesting technique using electroflocculation was carried out at different voltage treatments (4, 7, and 9 V) using a fabricated voltage regulator and compared with harvesting by electroflocculation at 12 V using a car battery to efficiently electroflocculate Tetraselmis tetrathele. This study was conducted to determine the ideal voltage settings that could improve the quality of harvested paste in terms of nutritional value and metal contamination for its later use in aquaculture. The use of 7 V achieved low Pb content producing the best harvest biomass (1.4 kg, 87 min) which is comparable to the harvest biomass (1.7 kg, 68 min) using a 12 V car battery. Storage of T. tetrathele paste is best done in a chiller (2 ± 1 °C) rather than a freezer (-20 ± -4 °C) for ease in reactivation and maintaining higher cell viability for later use as a starter in aquaculture. Storage in a chiller allows T. tetrathele paste to be resuspended after six months and used as a starter culture.