US researchers hope to reduce high aquaculture mortality rates

From: FoodBev Media

Researchers at Oregon State University (OSU) are developing a new technology to deliver water-soluble nutrients to aquaculture-raised fish, oysters, clams and shrimp that they hope will reduce the high rates of mortality that plague the industry.

As much as 80% of hatchery-reared larval marine fish die in their early life stages and researchers aren’t exactly sure why, according to Chris Langdon, a professor of fisheries at OSU’s Hatfield Marine Science Center and principal investigator on the project.

One prevailing theory, he said, is that the critical water-soluble vitamins and amino acids rapidly leach from their tiny food pellets into the water.

“We’re having some success by packaging water-soluble nutrients into liposomes that we use to enrich the live feeds – for example, brine shrimp – or put inside of food pellets,” Langdon said. “The next step is to expand the project and look at how it affects different fish species, and whether we can make it cost-effective.”

Langdon and his colleagues have received a three-year, $630,000 grant from the National Sea Grant programme to conduct further tests. The study is important, the scientists say, because the US has a major seafood deficit, “importing more than $11 billion of seafood products annually from other countries”.

Aquaculture will be critical in the future to produce protein for the world’s growing population because many wild stocks of fish have already reached their peak levels of sustainable harvest, Langdon noted. However, most marine fish hatcheries are not efficient models of production, he added.

“If we can halve that mortality rate – and I think we can – it would be a game-changer,” Langdon said.

The key to the preliminary success by the OSU scientists lies in production of liposomes, which are tiny vesicles, or bubbles, made out of the same material as a cell membrane. These liposomes are said to be very efficient in containing nutrients – and other products – despite their small size.

For example, the pellets used to feed larval aquatic animals are often smaller than a grain of sand, making them difficult to enrich. In recent years however, OSU researchers have managed to incorporate liposomes that are filled with nutrients.

Langdon added: “We also can fill the liposomes with other substances, such as growth-promoting agents, vaccines, or vitamins to boost the animals’ immune systems and reduce stress.

“In addition to aquaculture for food species, there is a potentially huge opportunity to improve the survival and health of ornamental fish for the aquarium industry that is worth billions of dollars.”

Langdon and Hawkyard are working with the Hubbs-SeaWorld Research Institute in San Diego to broaden the scope of their study, focusing on improving growth rates and reducing losses in California yellowtail, sea bass and ornamental fish.

 

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