Sea Lice Research

Sea lice are a naturally occurring crustacean parasite that attach themselves to a fish host, such as Atlantic salmon. These parasites have co-evolved with their hosts for millions of years and, as a result, they are very good at finding a host, particularly when the hosts are in high concentrations, such as salmon in sea cages.

Sea lice infestation or outbreaks, which have been a recurring problem in salmon aquaculture over the last two decades, must be managed with treatments to maintain animal health. These infestations are a significant cost for the industry and are of concern for their potential impacts on the marine environment. Evidence shows that sea lice can develop resistance to existing chemical treatments, which is similar to land-based pests that impact the agricultural industry.

Sea lice are a naturally occurring crustacean parasite that attach themselves to a fish host, such as Atlantic salmon.Sea lice are a naturally occurring crustacean parasite that attach themselves to a fish host, such as Atlantic salmon.

For salmon farming in coastal waters, it is still not clear how the larval planktonic sea lice complete their life cycle. After being released from their mother’s egg sac, the tiny, slowly swimming larvae drift away but are somehow able to find their way back to a salmon farm despite the large volumes of sea water that pass through the site.

Larval sea lice, or nauplii, as seen under a microscope.Larval sea lice, or nauplii, as seen under a microscope.

With funding from the Aquaculture Collaborative Research and Development Program, Station researchers are:

  • studying the distribution and infestation dynamics of sea lice on salmon farms;
  • testing green technologies based on mechanical strategies of removal to reduce dependence on chemicals for control and removal of sea lice from salmon; and
  • working with industry to develop methods, such as warm water showers, to remove and capture the lice to reduce their occurrence at cage sites and to try and break the cycle of infestation.

This research will provide scientific advice on options for improved farm-management activities and sea lice treatment approaches that help minimize the potential for harmful environmental impacts.

Early indications suggest that the effectiveness of the warm water shower to remove sea lice from adult salmon, and then capturing the lice with filters, may significantly reduce their ability to re-infest the farm site. However, there is concern that sea lice may develop a resistance to warm water similar to the resistance that has developed to chemical treatments. Unfortunately, simply increasing the water temperature of the shower is not possible due to potential negative effects on the welfare of the fish. Researchers are studying whether sea lice can develop a resistance to the warm water shower by selectively raising generations of sea lice that have been exposed to higher temperatures. Should the sea lice show signs of adapting, it will provide further information on the effectiveness of the warm water shower technology.

Our researchers have also been studying the potential to select Atlantic salmon broodstock (fish that are mated to produce offspring) that are more resistant to sea lice infection. The goal is to allow industry to determine genetic markers that may be linked to better resistance, and develop broodstock that will produce offspring that are better at resisting sea lice infection.

Additionally, work is underway to test whether sea lice removal behaviour in Lumpfish, a natural cleaner fish, can be passed on from generation to generation. If so, the potential for using these fish as a natural control of salmon lice may become more efficient and help reduce the need for chemical treatment of the pest.

For more information on these projects, please visit the Aquaculture Collaborative Research and Development Program.