Fish farming could be linked to an increase in fish disease. This is according to researchers at the University of Bergen in Norway, who studied a group of Atlantic Salmon infected with salmon lice. They found that the group of Salmon raised at two Norweigian farms actually had worse cases of lice than those living in the wild, The Scientist reported. The study’s findings were published in the Journal of Evolutionary Biology this April.
The results highlight the difficulty many farmers and ranchers face in caring for their animals, as infectious diseases and pests can quickly spread throughout an entire herd, or in this case, a school.
“Salmon lice from areas with fish farming appear to have evolved toward a higher virulence as compared to salmon lice from other areas,” Arne Skorping, co-author of the study, wrote in an email statement to The Scientist.
The Scientist also reports that aquaculture produces nearly half of consumable fish, but the conditions may also increase the presence of disease. Tommy Leung of the University of New England said in a statement to The Scientist that the cramped conditions of fish farms are prime breeding grounds for the spread of pathogens and parasites.
“The environment of intensive culture — stressed, genetically homogenous animals packed in high density conditions — is practically a recipe for cultivating highly virulent parasites,” he said.
The aquaculture industry has been subject to tight regulations in order to combat both conditions like these as well as over-farming. In the United States, the National Oceanic and Atmospheric Administration instituted the National Shellfish Initiative in 2011 to protect these marine animals and increase the population. This effort has been mirrored by many state governments, too. The Louisiana Department of Wildlife and Fisheries, for example, outlaws the commercial harvesting of blue crabs in state waters for a 30-day period every year.
Sundberg said in a statement to The Scientist that intentional efforts are the key to preventing the spread of disease on farms. She said that aquaculture professionals can lower farming density, increase separation between wild and domestic fish, and let farmed waters recover after a harvest.
“Making host-to-host transmission as difficult as possible will give fewer chances for natural selection to act in favor of virulence,” Sundberg said. “In the longer term, aquaculture needs to rely more on evolutionary science to achieve sustainability.”