Stress in the larval stage can make farmed fish more resilient later in life

There are many methods that are used to ensure that farmed salmon thrive, stay healthy, and grow quickly. Nofima scientist Erik Burgerhout is working on programming the fish to become robust.

Nofima’s research will harness epigenetics to make fish more resilient. The Programming Fish for Robustness (Progress) research project exposes fish to stressors such as low temperatures and low oxygen levels in the early stages of life, prompting them to develop their own genetic material – l ‘RNA – to better resist stress later in life.

“To produce robust farmed fish, we have to go back to nature. Cold temperatures are natural for wild salmon, so it is actually the relatively high temperature normal to fish farming that is the stressor. We are currently carrying out research to understand what is behind these mechanisms, ”explains Erik Burgerhout.

“We have noticed that low oxygen levels – hypoxia – affect fish. The question is whether low oxygen levels early in life would program fish to resist low oxygen later in life, while improving the immune system of the fish, ”explains Erik Burgerhout.

The role of stress

Stress during the early stages of life can have a serious impact on the development, growth and behavior of various groups of animals, including fish. However, there is currently little knowledge about the epigenetic regulatory mechanisms involved – that is, in this case, whether the impact of stress causes the fish to develop its own robustness throughout its life, and the level of stress that is justifiable from an animal welfare perspective.

In the Progress project, salmon were exposed to low levels of oxygen during the embryonic / larval stage. Later, the same fish were studied for their survival in the seawater phase, growth and resistance to disease. According to Burgerhout, the results did not quite live up to expectations.

“We measured the fish’s tolerance to low oxygen levels and studied the development of its immune genes during smoltification. In addition, we studied the immune response after exposing fish to pathogenic bacteria feared in the aquaculture industry. We only managed to see small differences between fish that were exposed to stress with little oxygen early in their life and fish that had not had this type of impact. We do not consider these negative results, but rather results without the expected impact. More studies are needed before we can say anything with certainty, ”says Erik Burgerhout.

“Although we found little difference between the groups regarding the hypoxia challenge test, the results suggest that chronic hypoxia in the first phase of life stimulated immune genes and attenuated their downregulation. related to smoltification, however these changes did not improve protection against a bacterial pathogen, ”he said.

Project results show the potential for using environmental stimuli as treatments to shape gene regulation in farmed salmon.

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