Cleaner Wrasse: Biological Pesticides to Combat Sea Lice

Cleaner wrasse eat dead tissues and parasites off larger fish

Sea lice are one of the largest challenges facing the salmon farming industry, and current treatment methods to combat these parasites involve chemicals that can have harmful effects on the environment.  However, an answer may be on the horizon: it has been found that cleaner wrasse, a group of fish found naturally all over the globe, have the ability to eat sea lice directly off infected salmon, thus reducing the need for chemical treatments.

In nature, cleaner wrasse form symbiotic relationships with other fish: the wrasse eat dead tissues and parasites off of the fish, which in turn enjoy the benefits of disinfection.  By placing wrasse in salmon cages, fish farmers can help mimic this natural relationship, moving towards more sustainable means of parasite control.

This concept is not new to the industry, but with the increasing pressure from governments and environmental groups to decrease the levels of chemicals used on farms, aquaculturists are taking a renewed interest in the use of wrasse as biological pesticides.  While the introduction of another species into salmon cages has challenges and impacts of its own, the wrasse seem to reduce overall numbers of sea lice and help curb their spread.  Additionally, if they can’t find any lice to eat, it has been demonstrated that the wrasse will start to eat the bio-fouling organisms that settle on the nets, which has even greater implications for improved water flow through the system.

In an effort to shift towards sustainability of operations, wrasse should be more heavily researched and if their benefits mirror the initial studies, their use as biological pesticides should be implemented in salmon farms as soon as possible.