Barramundi Group has harvested all its Asian sea bass and stopped stocking its three ocean-based farm sites with juvenile fish. - BARRAMUNDI GROUP
SINGAPORE (The Straits Times/Asia News Network): A deadly fish virus has cast a pall over the future of sea bass farming in Singapore after forcing the Republic’s only fish farm operator in its southern waters to halt commercial production, The Straits Times has learnt.
This comes amid efforts to boost local seafood production to help the country produce 30 per cent of its nutritional needs by 2030, with the Singapore Food Agency (SFA) eyeing more sites in its southern waters for aquaculture.
As at June 2023, Barramundi Group has harvested all of its Asian sea bass, also known as barramundi, and stopped stocking its three ocean-based farm sites with juvenile fish due to outbreaks caused by the scale drop disease virus (SDDV).
The pathogen, which occurs naturally in Singapore and parts of South-east Asia, can kill more than half a pen of barramundi, which is often touted as the salmon of the tropics.
Responding to queries from ST, SFA said last Wednesday that farms in the Johor Strait – where the majority of Singapore’s fish farms are located – occasionally reported signs of the virus, which results in scale loss and fin erosion, among other symptoms.
Apart from barramundi and yellowfin seabream, the virus is not known to infect other species of fish. A 2021 study suggests that SDDV affects farmed yellowfin seabream.
Barramundi Group’s annual report for financial year (FY) 2022, published on June 23, states that farming at its Singapore sites off Pulau Semakau, Pulau Senang and St John’s Island will be held off until “an efficacious vaccine is available, for animal welfare and ethical reasons”.
A presentation by the group in February reported that an SDDV outbreak at its Semakau site in December 2021 caused elevated mortalities among farmed sea bass that lasted throughout the first quarter of 2022, with the site harvested out later in the year.
In response to queries by ST, Barramundi Group said the virus has caused “significant mortalities and financial losses” for its operations in Singapore. It recorded a loss of $31.9 million for FY2022.
Brunei will become Barramundi Group’s base for fish production, and the harvested sea bass will be processed and shipped to Singapore and international markets, the FY2022 report added.
“Our Singapore operations will continue to focus on aqua-tech capabilities such as vaccine and therapeutics development, veterinary and animal health, broodstock (fish used for breeding purposes) research and development, and the supply of high-quality fry and fingerlings,” a spokesman for the company told ST on July 18.
The firm operates a hatchery, nursery and broodstock facility at SFA’s Marine Aquaculture Centre on St John’s Island, and the juvenile fish are sent to research institutes and other local fish farms.
There are plans to export fish fry, or newly hatched barramundi, to places including overseas farms.
In 2020, Barramundi Group sold 377 tonnes of Asian sea bass produced in Singapore, or about 9.5 per cent of locally produced fish that year.
SFA said SDDV typically affects larger fish, and farms that grow sea bass to larger harvest sizes will encounter more deaths.
“With our limited sea space, aquaculture farms are often clustered closely. The practices of one farm are likely to affect most farms within the area,” the agency added, reminding the farms to monitor water quality and the health of their fish, to prevent the spread of diseases.
SDDV is not known to be transmissible to humans.
Lead scientist Saravanan Padmanabhan of Temasek Polytechnic’s Aquaculture Innovation Centre said infected but asymptomatic sea bass are safe to eat, as long as the scales are removed and the meat cooked thoroughly.
To boost the health of farmed fish, SFA will launch the Aquatic Animal Health Services in the third quarter of 2023, under which farms can have access to agency-funded consultations and disease investigations over the next four years.
There are currently no commercial vaccines or drugs for SDDV. Institutes here are in a race against time to develop them, given how rampant the virus is locally, said Dr Sunita Awate, research director of fish health company Uvaxx, a subsidiary of Barramundi Group.
According to SFA, SDDV was first formally described in farmed fish here in 2011. Before SDDV was identified in 2015 as the pathogen causing the disease, there had been reports of Asian sea bass showing scale-dropping symptoms in neighbouring countries since 1992.
Work on a vaccine is in the early stages, since the virus was identified only eight years ago by a pharmaceutical firm, said Dr Sunita.
Since 2021, Uvaxx and the Agency for Science, Technology and Research (A*Star) have been funded by SFA to develop vaccines against the sea bass-targeting virus.
So far, promising results have been seen in early immunisation trials to study whether vaccines can protect the fish species, said Professor Ren Ee Chee, senior principal scientist at A*Star’s Singapore Immunology Network.
The network and A*Star’s Infectious Diseases Labs are working on further trials.
Barramundi Group had also worked with an animal health conglomerate to trial a potential vaccine candidate in Singapore.
“However, the field trials are not completed as funding for additional field trials has yet to be secured. Hence, the results are inconclusive,” said the company’s spokesman.
Alongside institutes such as James Cook University and Republic Polytechnic, Uvaxx and Barramundi Group are working on a selective breeding programme to produce future generations of barramundi that can be naturally resistant to the virus.
Uvaxx has also partnered with an Israel firm to create an oral drug that could cure afflicted fish. Lab trials will start in August, said Dr Sunita, who is also Barramundi Group’s chief veterinary officer.
Malcolm Ong, chief executive of The Fish Farmer, which has four farms across the Johor Strait, said SDDV affected his barramundi previously.
But the outbreaks did not hurt his business much because he also rears other types of fish like red snapper, milkfish and mullet.
While the virus seems to result in a larger economic burden on aquaculture firms that farm only barramundi, there is the risk that it can affect other kinds of fish.
Dr Saravanan said: “SDDV, though mostly reported in Asian sea bass and yellowfin seabream for now, may adapt and migrate to other farmed fish species in a polyculture farming environment.”
He noted that the virus alone is unlikely to have too big of an impact on Singapore’s 2030 goal, because other marine fish species and crustaceans grown on land and at sea are not affected by it.
But SDDV is just one of many pathogens affecting farmed fishes.
“We have farms producing sea bass, marine tilapia and hybrid groupers, and have not hit positive SDDV over recent years, but have encountered other (issues) like infectious spleen and kidney necrosis virus.
“Land-based farming can mitigate SDDV with proper water quality management, until a vaccine becomes available in the market,” Dr Saravanan added.
