Promoting tropical eel culture in the Philippines: Comparative performance of Anguilla bicolor pacifica and A. marmorata in captivity

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

Complete genome sequence of Vibrio parahaemolyticus strain PH1273, isolated from aquacultured shrimp in the Philippines

We announce the complete genome sequence of Vibrio parahaemolyticus strain PH1273. This strain was collected from a Penaeus vannamei pond in the Philippines in 2015. Genome analysis revealed that it lacks the gene pirAB responsible for causing acute hepatopancreatic necrosis disease but encode multiple secretion systems and the associated effectors

Preliminary assessment of genetic variation in the Japanese endemic freshwater crab, Geothelphusa dehaani, based on mitochondrial DNA sequences

Suppl. material 1: Maximum Likelihood tree (Download file) Suppl. material 2: Matrix of pairwise differences of FST (Download file)Geothelphusa dehaani, a freshwater crab species endemic to Japan, has the largest distribution range amongst the 19 known species in the country. Due to its low dispersal capability and restricted habitat to freshwater, it serves as an excellent model for understanding gene flow between geographically isolated populations. In this study, we analysed the genetic relationships of 26 G. dehaani populations collected from different locations in the Japanese archipelago using two mitochondrial DNA regions - cytochrome oxidase subunit I (COI) and cytochrome b (cytB). Our results from the analysis of molecular variance (AMOVA) revealed high genetic variation amongst populations and the phylogenetic analysis identified four geographical groups: Clade I - Honshu and Shikoku, Clade II - north-eastern Kyushu, Clade III - southern Kyushu and Clade IV - north-western Kyushu. Notably, Clade IV exhibited the highest genetic distance amongst the observed groupings. These findings highlight the need for further examination of G. dehaani in Kyushu, including morphological and behavioural traits, to better understand the observed diversity within the species in the region.This research received support from research grants (KAKENHI-Grant Number JP21H05181) and the Ministry of Land, Infrastructure, Transport and Tourism of Japan

Inclusion of live mud polychaete (Marphysa iloiloensis) in the feeding regime improved the hatchery performance of domesticated Indian white shrimp (Penaeus indicus)

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.This study was supported by SEAFDEC/AQD (Study Code: DP-02-C2017T)

Black tiger shrimp revival program stepping up at AQD

As a highlight of its 50th anniversary, the SEAFDEC Aquaculture Department (AQD) inaugurated its new Black Tiger Shrimp Broodstock Facility in Tigbauan, Iloilo, Philippines on 3 July 2023. The biosecure facility was built to reduce reliance on wild shrimp spawners that often carry diseases which are then passed on to their eggs and larvae. Its four 120-ton broodstock tanks, with a combined holding facility of 1,440 fully-grown breeders, are projected to produce 80 million postlarvae annually. More importantly, it is hoped to be a source of disease-free captive broodstock which is critical to achieving high survival rates and the production of high-quality postlarvae in the hatchery

Effect of diet isotopic ratios on the δ13C and δ15N signatures of scallop-gut contents in a natural setting

The relationship between diet isotopic signatures and the extent of the tissue-diet isotope fractionation factors have been shown previously in controlled feeding studies, but this relationship remains poorly resolved for marine invertebrates in a natural setting. Using isotope analysis of gut contents, this study investigated the variability in tissue-diet isotopic fractionation factors (Δδ13C and Δδ15N) between scallop tissues (i.e. muscle and digestive gland) and gut content in the Japanese scallop Mizuhopecten yessoensis (Jay, 1857) and assessed how the growth rate of juvenile scallops and gut content quality (as carbon to nitrogen (C/N) molar ratios) would affect the values of tissue-diet isotopic fractionation. Tissue-diet isotopic fractionation factors (Δδ13C and δ15N) varied according to tissue, which averaged 1.7‰ and −0.1‰ for N in muscle and digestive gland, and 3.4‰ and 1.2‰ for C in muscle and digestive gland, respectively. Muscle-gut δ15N isotopic factors negatively correlated with growth rate, suggesting that the juvenile δ15N signatures were strongly dependent on food quantity. The influence of diet quality on δ15N was also evident, where δ15N decreased as C/N molar ratios in gut contents increased. The wide difference in Δδ13C and δ15N from accepted standard values may be, in part, a consequence of using gut contents as a dietary proxy. Results of this study have implications for diet reconstruction studies of this scallop species reared under field conditions

Nursery and grow-out culture of snubnose pompano (Trachinotus blochii, Lacepede) in brackishwater ponds

This manual, titled “Nursery and Grow-out Culture of Snubnose Pompano (Trachinotus blochii, Lacepede) in Brackishwater Ponds,” includes culture techniques and good practices developed through extensive research done at the Aquaculture Department of the Southeast Asian Fisheries Development Center. The manual also tackles a viable technology that can guide fish farmers in raising pompano in brackishwater ponds.This research is funded by SEAFDEC/AQD under the study code TV-05-F2021D

Phytochemical composition antioxidant and antibacterial activity of the Philippine marine green alga (Ulva pertusa)

The phytochemical constituents, total phenolic and flavonoid contents, antioxidant and antimicrobial activities of the ethanolic extract of the marine green alga Ulva pertusa collected from floating fish net cages off the coast of Guimaras island, Philippines, were investigated. Qualitative phytochemical analysis revealed the presence of bioactive compounds including alkaloids, flavonoids, phenols, saponins, tannins, and terpenoids. Quantitatively, total phenolic and flavonoid contents of the extract were 20.54±2.08 mg gallic acid equivalent (GAE) g-1 and 539.07±6.36 mg rutin equivalent (RE) g-1, respectively. The antioxidant activity of the extract using 1,1-diphenyl-1-picrylhydrazyl (DPPH) assay exhibited a concentration-dependent radical scavenging capacity. Additionally, the ethanolic extract inhibited the growth of Staphylococcus aureus ATCC25923, Escherichia coli ATCC25922, Streptococcus agalactiae, Aeromonas hydrophila, A. sobria, and Vibrio harveyi in a concentration-dependent manner with strong inhibitory activity at 100 mg mL-1 concentration. Taken together, U. pertusa contains bioactive compounds that possess potent antibacterial activity and remarkable antioxidant capacities. These substances are promising candidates that may be utilized in the synthesis of novel drugs.This study was funded by the Government of Japan Trust Fund V through the Regional Disease Project (study code: FH01-F2010-T) and partly by SEAFDEC AQD

Viral encephalopathy and retinopathy

Viral nervous necrosis (VNN), also referred to as viral encephalopathy and retinopathy (VER), has been reported in at least 120 cultured or wild marine and freshwater fish species and has caused serious economic losses among farmed marine fish species in the past decades. Since the first description of this disease at the end of the 1980s, substantial amounts of researches have been instrumental in understanding the mechanisms involved in fish infection, development of reliable diagnostic methods, and disease prevention and control. This chapter presents some important aspects of the disease with particular emphasis on etiologic agent, clinical signs and gross pathology of the disease, histopathology, disease risk factors, virus propagation and identification, molecular diagnostics, and concomitant prevention and control methods