Innovation — Wrasse
For all salmon, sea lice are a persistent problem. Like dogs and fleas, they’re just too things that go together, and keeping the salmon happy and pest-free is one of the main challenges for the farmer.
Conventionally, medicinal solutions have been used to clear the sea lice from salmon, but environmentally-minded researchers and farmers have been looking for another way, a means of treatment that would be as natural and un-stressful as possible for the animals without adding anything undesirable to the marine system.
When looking for an environmentally sound solution, sometimes nature is the best guide.
Out trap-catching wrasse in nearby waters.In the wild, there exists a relationship between salmon and another smaller fish that shares the same habitat — wrasse. Wrasses are a “cleaner fish,” and they have evolved to eat the sea lice directly off the salmon without causing harm or distress. In fact, wrasse like eating sea lice so much that they make it their mission to find every last one.
For the past few years, studies have been conducted in Scotland, as well as in Norway, on the efficacy of wrasse for sea lice control. Early findings have shown promise, and at Wester Ross we pride ourselves on striving for continuous improvement in how we raise our fish. So, in the spring of 2014, we started a wrasse program of our own.
Putting the wrasse to work in the salmon pens.Instead of introducing farmed wrasse into our pens as other pilot projects have done, we have gone one step further to draw on the population of wrasse living right in our local area. Ballan and rainbow wrasse are native to the waters around Wester Ross. The fish live close to the rocky shoreline and are easily trapped. On weekend wrasse missions, team members Tess and Keian go out and trap-catch local wrasse to bring back to the salmon pens. The smaller fish — what would fit in the palm of your hand — are the ideal size to live among the salmon.
Carefully trapped and then released into the pens at the farm, they swim freely among the salmon and get to work using their powerful jaws to eat the lice directly off of the salmon’s skin. These little fish are so efficient that one wrasse can easily tend to 50 salmon.
While the wrasse are in our care, we make sure their needs are met too. Wrasse are active during the day and like to rest at night, so the Wester Ross team has built secure hides for the wrasse to rest in when they are not busy at work.
By all accounts, the wrasse program has been, and continues to be, a great success. We have great hopes that incorporating wrasse into the life of the farm will eliminate any need for medicinal sea lice control in the future.