Selective salmon breeding fights sea lice

Sea lice are the biggest threat to the welfare of farmed Atlantic salmon and the sustainability of fish farming worldwide. Currently, chemical treatments are the main way of controlling infection, but growing drug resistance among sea lice means an alternative is urgently required.

Now, scientists at the University of Glasgow have now developed a “simple” protocol to breed fish that are resistant to sea lice and have produced a mathematical model to predict the response to selection.

“Our research has produced a practical tool for quantifying resistance to sea lice and shown that selection could substantially reduce the need for drug treatments,” said Professor Michael Stear. “The results indicate that fish respond quickly to selection and resistant fish populations will require substantially fewer treatments to control lice.”

The sea louse can cause skin lesions, osmotic imbalance and increased susceptibility to bacterial and viral infections through suppression of the host immune system.

According to the research, in some instances as few as 10 generations may produce fish that naturally control infection and seldom require treatment.

Chemical treatments of salmon to protect against sea lice varies from country to country but amounted to losses of US$480m per annum worldwide in 2006.

“Selective breeding for sea lice resistance should reduce the impact of sea lice on fish health and thus greatly improve the sustainability of Atlantic salmon production,” Professor Stear concluded.