This being something aquaculture companies and governments around the world are continuing to research, in the combined hope of ensuring a sustainable salmon farming industry of the future.
Current approaches
One of the main currently used non-pharmaceutical approaches of sea lice control is the use of so called ‘cleaner fish’; artificially introduced species that live alongside the salmon and feed on the sea lice attached to them.
Numerous salmon farms throughout Canada, Norway and Scotland are currently using this approach as part of an integrated pest management system; with wrasses, also known as connors or cunners, being the principle cleaner fish of choice.
Whilst offering some potential in the multifaceted battle against sea lice control however, wrasse use is not without its limitations; the fish are particularly sensitive to cold water temperatures - making them unsuitable for use in many farms, especially the salmon farms of Northern Norway.
Furthermore this sensitivity prevents wrasse from feeding in the winter and can lead to mortalities. The fish themselves are also found to be slow growing, and the need to produce multiple species and sizes to be used alongside various salmon sizes, adds another level of complexity.
More recently however, evidence has shown that lumpfish, or lumpsucker fish as they are also known, have been found to feed on sea lice. A number of governments, aquaculture companies and marine organisations around the world, are now researching this species as an alternative, and additional, cleaner fish to be explored and exploited in the ongoing battle of sea lice control.
Advantages over wrasse
The use of lumpfish offers several main advantages over wrasse. One of the main such benefits being that they are more robust and hardy, with greater temperature range tolerance and the ability to feed all year round.
A 2011 trial under the NORDLUS project of Norway (the Norwegian company Akvaplan-niva, in association with Nordlaks Oppdrett AS, Codfarmers AS, and the aquaculture research station Gildeskål Forskningsstasjon AS) for example, found lumpfish to actively feed on sea lice even in the depths of winter; water temperatures at such time reaching lows of between 4-7°C.
Another key benefit is the faster growth rate of the species. Initial trials report lumpfish of suitable size (5-6 cm) to be produced within 4 to 5 months - this in distinct comparison to the 1.5 years required to produce equivalent wrasse of an appropriate nature.
The lumpfish themselves also reportedly being easier to farm, and once reared, can be used at a greater density than wrasse (10% compared to 4%), as well as being less susceptible to vibrio infection.
The same above NORDLUS trial also interestingly reporting lumpfish to have an insatiable appetite for sea lice, and even for them to have a pacifying effect upon the salmon themselves.
The future?
Whilst never claiming to offer a solution, the promising results of lumpfish initial trials indicate the potential of the species as an additional tool in the ongoing fight against sea lice. This potential being something the world of aquaculture is keen to explore, with a number of research projects currently under way.
The Newfoundland government of Canada for example, announced on the 6 August 2013, that they will be donating C$85,000 to continue a combined research effort involving Memorial University, the Canadian Centre for Fisheries Innovation and representatives from the aquaculture industry.
Shetland’s aquaculture industry is similarly receiving £300,000 of European funding to explore how lumpfish can further help in the battle against sea lice. Only time will tell the potential of this species and any additional possible benefit it could serve.
December 2013
