Tackling the Sea Lice Crisis in Salmon Farms

Victoria Lai

Walking past the seafood aisle, a row of trays attracts your attention. The beautiful orange flesh with its rich, fatty goodness sits below a yellow sign – “Fresh NZ Salmon”. It looks good, it seems fresh, and it is homegrown, so temptations are high. Naturally, you pick one up and head to the checkout counter. This transaction is easy, fast, and so convenient that it has become part of your weekly routine, and the apparent surplus of fresh salmon makes you doubt that this will end anytime soon. However, what if salmon suddenly disappeared from the shelves next week? What if the production of salmon suddenly comes to a halt?

Delicious looking salmon fillets in a market. Pixabay

Delicious looking salmon fillets in a market. Pixabay

As regular consumers, a routine trip to the supermarket would usually not involve these questions regarding the future of our food. Unfortunately, these hypothetical questions are becoming more and more relevant in our changing world.

The global consumption of fish in 2030 is currently projected to be 20 percent higher than the consumption in 2016. As a result, aquaculture production is expected to increase simultaneously to meet these demands. However, the production of fish in these high-density farms allow for diseases to thrive, potentially resulting in ecological and economic consequences. One of the worst culprits is a parasite, called sea lice.

Sea lice – scientifically known as Lepeophtheirus salmonis – are small marine ectoparasites. According to the University of Auckland scientist, Professor Mark Costello, sea lice are the most destructive parasites within the salmon farming industry. Sea lice have a parasitic relationship with salmonid species (such as salmon and trout) and they live by latching onto the bodies of their hosts to feed on their flesh and blood. This causes cuts, bleeding and skin infections and if left untreated, these symptoms can lead to death. Those fish that do survive are often left with unpleasant wounds, making them unmarketable.

In addition, the costs that are associated with researching and implementing treatments for sea lice result in another major issue for the aquaculture industry. Methods such as chemical or mechanical removal and predator introduction have been implemented in the past, and have proven to be effective in controlling and preventing sea lice numbers from increasing. However, these treatments are very costly. In 2006, the salmon farming industry spent at least €305 million on sea lice treatments. Because more salmon farms are being developed around the world to meet the needs of a growing human population, this suggests that more money will need to be spent to mitigate the effects of sea lice in future aquaculture initiatives.

The impacts of sea lice are larger than one might think. A study in British Columbia discovered that failure to control outbreaks in salmon farms might increase the chances of sea lice transmission into wild populations. Therefore, without proper treatment and prevention on aquaculture farms, the ecological impacts of sea lice may expand into the surrounding wild fish populations. These additional issues can make it difficult to estimate how broad the impacts of sea lice are. However, new methods are being researched to help develop ways of controlling and preventing rising sea lice numbers in aquaculture.

Aquaculture is predicted to contribute 65 percent of our fish needs by 2030 (FAO, 2018). Pixabay

Aquaculture is predicted to contribute 65 percent of our fish needs by 2030 (FAO, 2018). Pixabay

Researchers, led by Professor Mark Costello are using modelling technology to assist fish farmers in mitigating some of the impacts of sea lice. Through the use of a spatial distribution model, called MaxEnt, they hope to provide solutions to this complex issue. This model requires two components: the location of the sea lice and environmental factors. By changing the environmental factors, such as raising the temperature, the program will predict how this will affect the future distribution of sea lice.

Farmers may use this method in the same way we all use weather forecasts; weather predictions can help us prepare the appropriate outfit and adjust our plans accordingly. In this case, if the program predicts that sea lice number increases with an increase in temperature, for example, then this will suggest that farmers should expect a higher chance of sea lice infestation during warmer months. From there, they can choose to harvest their fish before sea lice season or apply a suitable treatment during the optimal time.

MaxEnt has shown promising results in past studies on parasites. Using Maxent, a recent study on the long-horned ticks found that the program was a useful and effective tool for predicting parasite distribution in agriculture. Therefore, this method can potentially be applied to aquaculture and become a valuable tool for farmers and researchers to design new management strategies for sea lice treatments.

So, the next time you are out on your weekly supermarket trip, be sure to consider and appreciate the amount of work that is necessary to prevent your produce from disappearing. And don’t forget to always check where your seafood comes from and whether its sustainably harvested!

Rising Tides is a series focussing on the current threats facing our ocean, how these are being tackled and what you can do to help