New findings on salmon response to hydrogen sulfide in fish farms
Researchers have studied how the mucosal surfaces of salmon, which are the first line of defense against environmental threats, react to prolonged exposure to low and non-lethal levels of H2S.
Researchers from Nofima and international collaborators have made important discoveries about how Atlantic salmon reacts to prolonged exposure to low levels of hydrogen sulfide (H2S) in recirculation systems (RAS).
The study “Mucosal organs exhibit distinct response signatures to hydrogen sulphide in Atlantic salmon (Salmo salar)”, published in Ecotoxicology and Environmental Safety, provides valuable information for on-land salmon farming. The results could have significant implications for the health and welfare of fish in these systems.
Hydrogen sulfide is a toxic gas that can form in recirculating aquaculture systems (RAS), particularly at higher salinity levels. Even low levels of H2S have been linked to health problems and mortality in salmon. The recently published study analyzed how salmon are affected by being in water with low amounts of hydrogen sulfide over an extended period, which can occur during normal production in RAS.
According to a press release by Nofima, researchers have studied how the mucosal surfaces of salmon, namely the skin, gills, and nose, which are the first line of defense against environmental threats, react to prolonged exposure to low and non-lethal levels of H2S.
One of the key findings made by the researchers is that when salmon are exposed to hydrogen sulfide, the gills and the olfactory organ in particular react by activating genes that help the fish cope with stress and trigger immune responses. Another finding is that the salmon's mucous membranes have the natural ability to detoxify hydrogen sulfide. Researchers also identified several protein markers in the skin and gill mucus that can be used for non-invasive testing of H2S response.
"Our findings suggest that salmon can largely adapt to the low levels of H2S we tested, without serious negative health effects. This is good news for the salmon farming industry, but also highlights the importance of careful control and monitoring of H2S levels in RAS facilities," stated project leader Carlo Lazado from Nofima. The results can contribute to improving the cultivation of Atlantic salmon in several ways. One of the most important points highlighted by the researchers in the report is the improvement of risk assessment and the establishment of threshold values for H2S in RAS facilities. In this regard, there is potential to develop new standards that strengthen the salmon's resistance to H2S exposure.
The study represents an important step towards a more sustainable and efficient on-land salmon farming, with a focus on fish welfare and production quality. The findings are particularly relevant for land-based fish farms, where H2S levels can be higher than in open sea facilities. By monitoring and controlling H2S levels, as well as implementing measures to strengthen the fish's natural defenses, fish farmers can ensure healthier and more productive fish.
Carlo Lazado will present more information about this research at the Smolt production in the future conference to be held in Sunndalsøra, Norway, on October 16 and 17, 2024.
