Fish farms in Sihanoukville have lost an estimated 100 tonnes of fish to an aquatic parasite infestation in the past five days, Fishery Administration officials said yesterday.

The parasite, known as “marine velvet” or Amyloodinaum Ocellatum, feeds on fish tissue – giving it a powdered look – while releasing toxins. According to Europe PubMed Central, marine velvet is “one of the most serious ectoparasitic diseases plaguing warmwater marine fish culture worldwide”.

While officials did not have exact figures, Nen Chamroeun, chief of the Fishery Administration in Sihanoukville, estimated the damage at 100 tonnes, because the parasite hit nearly 100 pens, each of which contains several tonnes of fish. Chamroeun said poor local conditions contributed to the outbreak.

“The seawater there started to get dirty,” he said. “After the fish died, we found that the fish had a parasite . . . causing them to stop eating food and have difficulties breathing.”

He said that officials and experts asked the fish owners to move their surviving stock to different pens and clean the contaminated pens.

The outbreak terrified local fish farmers like Teang Moa, the owner of 50 pens, who lost 4 tonnes of stock over the past few days. “For a few days, I wondered why my fish did not eat and later on, they died in our plot,” she said. “I am in a panic to see it. This is our livelihood.”

Moa, who has been raising her current stock for nearly a year, said she can usually sell a kilogram of fish for 26,000 riel (nearly $6.50). She tried to sell her dead fish this week but could only fetch 5,000 riel per kilo.

Despite the officials’ statement, she blamed the runoff from a nearby clothing factory, which “makes the water dirty”. Kiev Tha, a Fishery Administration official, said that there is no proof that the factory is involved and his colleagues are investigating the outbreak’s causes.

According to a 2008 University of Sydney study, the disease occurs especially in “small systems” and mortalities can be high.

The source of outbreaks is unknown but “may involve use of water from bodies which contain infected wild fish, introduced infected wild-caught fish or sporadic maturation of latent parasites”.

Prak Puthea, a police chief in Sihanoukville’s Commune 1 said that fish farmers should tell authorities when their fish stop eating.

Additional reporting by Igor Kossov