News & Views Fish Health Research
New Nofima test sheds light on smolt health

In September 2022, scientists at Norwegian food research institute Nofima announced the development of a new test that evaluates the immune status of Atlantic salmon smolts. Atlantic salmon require a robust immune system as they make the transition from freshwater to the ocean. But official estimates show that about 15 per cent die after being transferred from land-based freshwater tanks to net pens at sea. Hopes are high that the new test will help to develop measures to improve the smolts’ chances of survival at sea and benefit farms.

“The occurrence of infectious disease is highest during the first months after seawater transfer, and immune suppression can be one of the risk factors,” said Aleksei Krasnov, senior scientist at Nofima. “We have done transcriptomic analyses in many projects and built the largest gene expression database, which was used in this particular test for the selection of immune and stress genes for diagnostics. Smolt quality and health are two main factors that determine the success of salmon production, and assessing the immune system of farmed Atlantic salmon is particularly important during smoltification and the first several months at sea.”

Run on the Fluidigm Biomark HD platform, the test involves taking samples from the gills or dorsal fin to measure the activity of 44 immune and stress genes, two markers of smoltification and two reference genes that are analyzed simultaneously. Results are then compared with a large data set from high quality salmon, enabling Krasnov and his team to assess immune status and characterize any problems if the condition of salmon deviates from the norm.

“Companies and farms control smolt quality with a focus on osmoregulation, but our test offers them much more information,” said Krasnov. He and his team have designed a similar assay for skin health and are developing others using their gene expression database. They believe that their latest test could eventually be used for other salmonid species such as rainbow trout and Pacific salmons.

Nofima’s Fish Health group has a strong, broad competence in terms of methodology (in vivo and in vitro trials, genomics, microbiology, microscopy with artificial intelligence, bacterial metagenomics, etc.) and research topics (infectious and parasitic diseases, vaccines, traumas and wounds, effects of production protocols and environment). “Our goal is to bring good science to industry, and this requires knowledge of advanced methodology and challenges facing aquaculture,” said Krasnov.