Threshold infection level is the pathogen load of the test animals measured before the appearance of clinical signs and mortality. This study aims to establish the threshold infection levels of WSSV in different weight ranges of Penaeus vannamei using qPCR. Artificial infection experiments were conducted using four weight ranges (3–5 g, 7–8 g, 15–18 g, and 22–25 g). The LD₅₀ of the different weight ranges of shrimps were achieved at viral dilution of 10^-6 and 10^-5 after 216–240 hpi, and the viral loads of these inoculums have a range of 10⁵–10⁶ WSSV DNA copies/g. The viral loads of the samples in the timecourse infection experiments when the mortalities started was determined at 10⁹ WSSV DNA copies/g, while for the survivors was at 10⁶ WSSV DNA copies/g. The threshold infection level of WSSV in shrimp was determined at 10⁷ to 10⁸ WSSV DNA copies/g. It was also found out that the threshold infection level was not weight dependent.

Infectious diseases caused by viruses and bacteria are a major threat to sustainable shrimp farming globally. Since early 80’s viral diseases such as White Spot Disease, Taura Syndrome disease have caused enormous losses to shrimp aquaculture both in eastern and western hemisphere. As the shrimp industry tried to recover from the onslaught of these diseases, a bacterial, Acute Hepatopancreatic Necrosis Disease (AHPND), also known as Early Mortality Syndrome, and a fungal disease Hepatopancreatic Microsporidiosis (HPM) caused by Enterocytozoon hepatopenaei (EHP) are now posing new threat to shrimp aquaculture. Acute Hepatopancreatic Necrosis Disease is caused by Vibrio spp. expressing plasmidborne binary toxins, PirA and PirB that is similar to entomopathogenic bacterium, Photorhabdus encoded toxin. In 2009, AHPND emerged in China and since then spread to many countries in East Asia and in the Americas. Another disease that has caused alarm in recent year is Hepatopancreatic Microsporidiosis (HPM) caused by Enterocytozoon penaei (EHP), a microsporidium. While AHPND causes acute infection and large-scale mortalities, EHP causes chronic infection and results growth retardation and size variation in population reducing marketability of the infected shrimp. Both diseases affect hepatopancreas, an organ involved in metabolism and humoral immunity in shrimp. The binary toxin, PirA/ PirB are the primary virulence factor for AHPND, but specific virulence factor(s) for EHP is not known. It is, however, known that EHP does not have mitochondria and appears to transport ATP from the cytoplasm of infected cells as it contains ATP transporter genes in its genome. EHP has been shown to be a risk factor for AHPND. Due to lack of therapeutics, preventative measures remain as a corner stone for managing these diseases and efforts are underway to develop genetically improved lines of shrimp having resistance to AHPND and EHP.

Aquaculture is an important industry in Thailand which has been established more than two decades ago. The cultured species are divided into two main groups; shrimp and finfish farming. The major cultured shrimp species are Penaeus vannamei (Pacific white shrimp), P. monodon (black tiger shrimp) and Macrobrachium rosenbergii (giant freshwater prawn), whereas the finfish are Oreochromis sp., Lates calcarifer and Epinephelus sp. Also, ornamental fish such as Cyprinus carpio (Koi carp), Carassius spp. (goldfish), and Betta splendens (fighting fish or betta). Disease outbreaks are the key factor that affect Thailand’s aquaculture production and resulting in economic losses. The infectious diseases in aquaculture are mainly caused by viral and bacterial pathogens. In 2018, the reported shrimp pathogens are white spot syndrome virus (WSSV), yellow head virus (YHV) genotype 1, Taura syndrome virus (TSV), infectious hypodermal and haematopoietic necrosis virus (IHHNV), Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease (VPAHPND), and microsporidian Enterocytozoon hepatopenaei (EHP). On the other hand, the reported pathogens in finfish are Betanodavirus causing viral nervous necrosis (VNN), Tilapia lake virus (TiLV) and Streptococcus sp. etc. In Thailand, the Department of Fisheries (DOF) is the competent authority for various aspects of aquatic animals including aquatic animal health. Strategies to prevent and control diseases in aquatic animals include issuance of legislations/regulations, implementation of biosecurity measures, disease surveillance programs, capacity building, cooperation with international and national organizations. Moreover, DOF has developed contingency plan in dealing with aquatic animal disease emergencies through the provincial fisheries officer. The provincial fisheries officer acts as director of emergency aquatic animal disease control center in each province, while Aquatic Animal Health Research and Development Division (AAHRDD) and Songkhla Aquatic Animal Health Research and Development Center (SAAHRC) serve as disease diagnosis and laboratory testing centers. Because of the above actions, we are capable of preventing and controlling disease outbreaks in the country. But during the occurrence of some diseases, we have no treatment to support and completely solve the problem. Example are viral diseases, unlike bacterial diseases which can be treated by using chemical or drug. Furthermore, there are a few researches that could be applied in farm level. Especially shrimp which has no adaptive immunity, so it is difficult to develop vaccine compare to fish. Therefore, DOF mostly recommended farmers to follow the good management practices on aquatic animal health for promoting sustainable aquaculture.

The national aquatic animal disease surveillance and reporting system is implemented by the Bureau of Fisheries and Aquatic Resources in coordination with other recognized laboratories. It covers the OIE/NACA listed diseases particularly those that cause major problems in aquaculture. The fisheries laboratories continuously enhance their capabilities to support the surveillance activities, controls on transboundary movement of aquatic animals, and provide services to the fish farmers. Programs are implemented to strengthen the aquatic animal health services in the country. Promotion of Good Aquaculture Practice and implementation of biosecurity measures are being done to prevent disease occurrences. Collaboration with other institutions on aquatic animal health programs are also established. The paper provides the information on the country’s status on aquatic animal health management.

The fisheries sector of Malaysia plays a significant role in economic development. It provides employment, foreign exchange and protein supply for the country. In 2017, aquaculture production in Malaysia was 427,022 tonnes, a 4.8 % increase compared to 2016. The increase was driven by population growth, rising demand for seafood and a levelling of production from capture fisheries. However, the rapid growth of aquaculture has been source of anthropogenic change on a massive scale. Aquatic animals cultured in high density are exposed to environment stress leading to diseases. Among major diseases occur in Malaysia are TILV and Streptococcosis in Tilapia, Vibriosis in grouper, and APHND and EHP in shrimp. Losses due to these diseases were reported as USD 0.1 billion for APHND in 2011, MYR 1 million due to Streptococcosis in 2002 and USD 7.4 million in Vibriosis outbreak in 1990. Currently the use of chemicals to overcome these diseases by farmers has led to increase concerns on food safety of food fish. Thus, Malaysia has implemented strict biosecurity measures in fisheries practices to secure not only fish health but also food safety for the consumers. This paper aimed to discuss the status of fish diseases and national diseases response and surveillance in Malaysia.

Fish disease is one of the main obstacles in the success of aquaculture production because of the loss caused by it. The outbreak of diseases has resulted to a substantial economic loss which was reported to have reached almost USD 400 million. To minimize the impact of losses caused by fish diseases, the Indonesian government through the Directorate General of Aquaculture, Ministry of Marine Affairs and Fisheries has a fish disease monitoring and surveillance program. The program aims to monitor the occurrence of fish diseases in Indonesia, especially in the fish and shrimp farming centers and to educate on how to control them. In 2018, the monitoring and surveillance program have 34 provinces with 100 districts/cities location targets targeting fish and shrimp diseases. Based on the results of the monitoring and surveillance activities in 2018, the fish and shrimp are affected by the following diseases: White Spot Syndrome Virus (WSSV), Infectious Hypodermal and Haemotopoietic Necrosis Virus (IHHNV), Infectious Myonecrosis Virus (IMNV), Iridovirus, Aeromonas hydrophila, Streptococcus iniae, Streptococcus agalactiae, Edwardsiella ictaluri and Ichthyophthiriasis. The program to control fish diseases in order to minimize the losses has also been carried out by the government including trainings on the application of biosecurity, the use of vaccines, probiotics, immunostimulants and herbal medicines.

One of the major constraints confronting the sustainable development of the aquaculture industry in the world, particularly in Southeast Asia, is the availability of quality fish seeds for stocking in ponds and cages. With the unreliable supply from the wild, the establishment of fish hatcheries has long been recognized as a primary means of reducing pressure on wild stocks and plays a key role in supplying the demand for seedstock of fish farmers. SEAFDEC/AQD has been conducting a short-term training course on marine fish hatchery since 1985, in response to the growing aquaculture industry and the increasing demand for information on seed production of culturally important and high-value marine fishes such as milkfish, sea bass, rabbitfish, groupers, red snapper, and pompano. The training conducted last June 19–25, 2018 was attended by participants from Myanmar, Indonesia, Philippines, Tanzania, and Maldives. This 37-days training course aims to equip the participants, working in the government, academe as well as in the private sectors, with technical knowledge through lectures and practicals on fish broodstock management, spawning, larval rearing, natural food culture, fish health management, nursery and grow-out culture, special topics on hatchery design, recirculating system, among others, of milkfish (Chanos chanos), sea bass (Lates calcarifer), groupers (Epinephelus coioides and E. fuscoguttatus), mangrove red snapper (Lutjanus argentimaculatus), rabbitfish (Siganus guttatus) and pompano (Trachinotus blochii). The participants conducted monitoring, culture, and scaling up of natural food organisms (green algae, Nannochlorum sp. and brown algae, Skeletonema tropicum; sampling of fish broodstock for induced spawning, and larval rearing. The trainees successfully cultured, monitored the growth rate, and scaled-up the production of natural food organisms (green algae, Nannochlorum sp. and rotifer, Brachionus plicatilis) for fish larvae. At the end of each larval rearing runs, the trainees obtained the following percent survival rate: milkfish (12-33); snapper (7-13); rabbitfish (5-19); pompano (0.4-6); sea bass (26-40); and grouper (22-31). The trainees cited poor water quality in the larval rearing tanks, especially at the onset of the rainy season, as one of the main reasons for the low survival rates. Maintenance of good water quality during larval rearing is an important factor for the efficient operation of a fish hatchery. To ensure a sustainable fish seed production and high survival rates, critical water quality parameters should be monitored and maintained within optimum levels at all times. The trainees evaluated the conduct of the course and gave an overall rating of 4.46 (very good).

This study conducted participatory enhancement of abalone Haliotis asinina and sandfish Holothuria scabra stocks using hatchery-bred and reared seeds released in the shores of Molocaboc Island in multi-use buffer zone of Sagay Marine Reserve, Philippines. The Community-Based Resource Enhancement (CBRE) process, implemented continuously from 2006 to 2019, include social and biophysical preparation, formulation of fisheries management and governance strategies, release of hatchery-reared juveniles, monitoring and periodic assessment, and socioeconomic impact assessment. CBRE was implemented through a tri-party collaboration involving fisherfolks, local government and research institutions. The abalone and sandfish enhancement procedures comprised of breeding in hatcheries, rearing of juveniles either in nursery facilities or net cages in coastal areas, and release in enhancement areas. A total of 11,500 tagged abalone juveniles were released in 11 batches in a protected coralline site from 2011 to 2015. Monthly monitoring showed increase in abalone catch per unit effort (3 divers, 1 hour fishing) in the release site from 0–2 individuals during baseline in 2011 to up to 150 individuals until 2019, including spill-overs without tags. Meanwhile, 96,400 hatchery-bred and reared sandfish juveniles were stocked in floating netcages in 15 batches and later released in sea ranch where mean density increased significantly from 3 to 138 individuals/ha in 2015 to 2019. Gleaning should comply with locally instituted catch-size regulation to sustain the fishery. Additional project activities include the construction and operationalization of a smallscale solar-powered hatchery on-site; freeze-drying trials of abalone meat to improve market reach; and initiatives to replicate the project in Lahuy Islands in Caramoan, Camarines Sur. Aquaculture, through seed production, therefore plays a key role in enhancement of threatened high-value species. Resource enhancement benefitted the fisheries through participatory management and eventually provided spill-overs to supplement income of marginalized fishers.

Disposal of agricultural wastes are posing environmental hazards which leads to efforts of efficiently utilizing them. This study surveyed a sugar central and a fruit processing plant to collect data on the volume of wastes from representative agricultural crops (e.g. mango, citrus, pineapple, sugarcane, papaya and soybean) in the Philippines during the 2012–2013 and 2014–2015 seasons, respectively. Their potential use in aquafeed was examined in terms of nutritional quality, presence of anti-nutritional factors (ANFs) and pesticide residues. About 40 to 60 % of agricultural wastes generated after processing were peels, pulps or brans, seeds, bagasse, molasses and okara. Most of the agricultural wastes had high levels of fiber and carbohydrate, and low levels of protein, although okara (25 % crude protein) and citrus by-products (11–16 % crude protein) showed acceptable nutritional quality. ANFs such as lignin are largely present in all agricultural wastes, whereas high levels of phenols, and saponins and alkaloids were found in mango seeds and mango peels, respectively. Pesticide residues were detected only in mango and citrus peels but at levels below the maximum residue limits of FAO Codex Alimentarius. From both nutritional and environmental perspectives, agricultural wastes have potential use in aquafeed production but their suitability should be further elucidated in diets for omnivorous fish species such as tilapia.

This paper describes the present status of aquaculture in Japan. The production volumes of many of the wide variety of aquatic organisms cultured in Japan, including finfishes, bivalves, crustaceans and seaweeds, are on a continuing decreasing trend. According to the national statistical data published by the Ministry of Agriculture, Forestry and Fisheries, the total marine aquaculture production decreased by 20 % by volume in 20 years since 1996 (1.3 million t). In fed aquaculture of marine finfishes, productions of the red seabream (Pagrus major), Japanese flounder (Paralichthys olivaceus) and horse mackerel (Trachurus japonicus) have declined markedly in both volume and value. On the other hand, productions of Pacific bluefin tuna (Thunnus orientalis), which has been included in the statistics since 2012, is increasing remarkably because of the strong affinity of Japanese consumers and the dwindling wild population. Production of white trevally (Pseudocaranx dentex), which is recognized as a luxury foodstuff, is also increasing. Productions of yellowtails (Seriola spp.) and pufferfish (Tetradontidae spp.) are rather stable in terms of volume and value. International demand for yellowtails is growing, and the export is expanding. As for unfed culture of bivalves, productions of oysters (Crassostrea spp.) and Japanese scallop (Mizuhopecten yessoensis) were severely impacted by the Great East Japan Earthquake in 2011, and the production of the oysters, which is on a long-term decreasing trend, has not recovered to the level prior to the earthquake. Production of the major seaweeds (Pyropia yezoensis, P. tenera, Saccharina japonica, S. angustata and Undaria pinntifida) are all on a continuous decreasing trend both by volume and value. Inland (freshwater) aquaculture production is only about 3 % of the marine aquaculture production by volume. About 70 % of the freshwater aquaculture production value comes from Japanese eel (Anguilla japonica), which has been increasing since 2002 due to the increasing unit price despite the decreasing production volume. The insufficient supply of wild glass eel is a problem for the eel aquaculture. The reduced aquaculture production is partially due to socio-economic and environmental reasons. For fed aquaculture, increasing feed cost and international competition are the major issues. Diseases also remain to be a problem. Prevalence of vaccination has reduced the disease damage from about 10 to 4 % of the total production value since around 2000, but the emergence of new diseases continues to occur. Infectious diseases have long been a problem in kuruma prawn (Marsupenaeus japonicus) aquaculture. Red tides still occur almost every year, causing damages mostly in western Japan. For unfed aquaculture, the reduced production is considered to be related with oligotrophication of coastal waters. Intensive reduction of terrestrial nutrient loads by advances in wastewater treatment is thought to have reduced the seaweed productivity, as well as other primary production, resulting in reduced productivity of not only unfed aquaculture of bivalves but coastal fisheries in general. Social factors are also involved. Production declines of many of these species are partially attributed to the reduced labor force due to aging and insufficient recruitment of farmers. The number of management body of oyster aquaculture, for example, decreased from 4,349 in 1963 to 2,018 in 2013. Structure of aquaculture industry in Japan (mostly privately-owned small business) and strong Japanese currency bring about the weak international market competitiveness.