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Going Green: Send in the cleaners

Can helper species effectively and economically combat sea lice at salmon farms?

By James Wright
December 01, 2012

Of the roughly 25,000 fish swimming in each of four circular net pens moored off the coast of New Brunswick, Canada, perhaps the most important ones contained therein aren’t even salmon. For every 100 salmon being fattened to market size for restaurants and supermarkets internationally, there are about four or five cunners, a smaller fish that’s been sent in to do a simple job: Feast on sea lice, the finfish aquaculture industry’s most persistent pest. Think of them as ladybugs controlling aphids in a garden. 

Sea lice (Lepeophtheirus salmonis) have caused millions of dollars in losses for salmon farms worldwide — as well as bad publicity for one of Canada’s top supermarket chains. One way to get rid of them is a pesticide. Slice (emamectin benzoate) and Salmosan are two common and effective ones on the market, but aquaculture industry critics oppose the use of such substances, fearing dire consequences for other species, like lobsters, that live near the farm sites. 

There is, however, an alternative measure under development that doesn’t depend on chemicals and the early results are encouraging. Projects in Norway and Canada, at both the university and corporate levels, are turning to helper fish like the cunner (aka connor or bergall; Tautogolabrus adspersus) and wrasse to remove the lice that enter salmon farms; scientists at the University of Maine in Orono believe mussel rafts placed on the periphery of the finfish farms can also help, as larval lice have been found in mussel bellies and digestive tracts. 

Whether these so-called cleaner fish become a cost-effective method adopted industry-wide will become clearer in the future, but the upside is obvious. For now, it’s largely in the experimental stages in Canada.  

The four net pen sites in New Brunswick with cunners in the mix are under the close watch of Cooke Aquaculture this year, says Nell Halse, VP-communications for the Blacks Harbor, N.B.-based company. Lab trials by fish-behavior scientists also show that the scavenger cunners, themselves considered a pest by fishermen, are proving adept at removing lice that have latched on to salmon fins or bellies. 

The use of wrasse for such purposes is growing more common in Europe — Norwegian fish-farming giant Marine Harvest began breeding wrasse in 2009 — but the non-native species is not allowed in Canada; the native cunner, however, is. Cooke’s immediate goal is to evaluate the feasibility of breeding cunners to avoid depleting wild stocks, and even to explore the potential of a side industry. 

“Sea lice have been around as long as salmon have been around,” says Halse, adding that Cooke employs multiple treatment regimens to vanquish the pesky parasites if and when they are detected. “Ideally, you want a suite of tools to treat your farms properly. 

We’ve lost fish, but we’ve spent a lot of resources on finding alternative treatments that work. That is part of doing business. Some companies are prepared to do that.” 

Halse says bath treatments for the fish are effective, as are feed-based therapeutants like Slice. The baths require the use of well boats that vacuum the fish into a holding area to be washed with a mixture of seawater and hydrogen peroxide, a first-aid substance found in nearly every household. Cooke and other companies in Atlantic Canada have invested millions of dollars in well boats, says Halse. Their efficiency allows operators to use far less chemicals than in the past, thereby limiting environmental impact. 

“[Pesticides] become less effective the more you use them — it’s an accepted agricultural principle,” says Halse, adding that every tool in the fight against sea lice has its benefits, citing years of research. “Different treatments attack different lifecycles of the parasite. We know how to use [pesticides] more effectively now.” 

A researcher at Memorial University in St. John’s, Newfoundland, has big hopes for the little cunners, which need to be at least 5 or 6 inches in length to fulfill their intended duties. Danny Boyce, facilities and business manager at the Dr. Joe Brown Research Aquatic Building, part of the school’s Ocean Sciences Centre in Logy Bay, says cunner-breeding research is in its early stages, compared to how far along wrasse research has come in Norway. Boyce hopes to know for sure within three to five years whether the species is up to the task and whether it’s economically feasible to raise in captivity for eventual deployment at the farms. His team is looking at the species’ biology, its spawning behavior and the best diets, the same process for any other farmed species.

“It’s another tool in the toolbox to mitigate sea lice,” says Boyce. “If a new bath treatment came out today that was effective, people might shy away from this. Companies are looking at things other than therapeutants, which are costly. It’s a matter of the industry wanting to support the research and development in this area. We can easily multiply to a large-scale project if need be. I’m hoping we can make this work.” 

When sea lice are removed by any method, the salmon generally do fine and recover quickly. Human health is not considered to be at risk from sea lice — it’s more of a fish-health issue. But if a salmon with a louse attached ever made it to market, it could mean bad publicity. 

Which happened in October when a customer at a Sobeys in Truro, Nova Scotia, posted a photo on Sobeys’ Facebook page of sea lice on a whole Atlantic salmon on display in the store. The company pulled all whole Atlantic salmon from 84 Atlantic Canada stores. 

According to company spokesperson Cynthia Thompson, only 80 whole fish were removed in total. The incident prompted Sobeys to take a closer look at its quality-control processes with its seafood wholesalers. Thompson reaffirmed the company’s support for the farmed salmon industry, saying in late October that it would be “days” before whole fish return to display cases, not weeks.

“It’s been a lightning rod for a broader discussion about aquaculture that continues and has been strong in parts of Atlantic Canada,” says Thompson. “But aquaculture is the future. We’re going to figure it out.” 

Email Senior Editor James Wright at jwright@divcom.com

Find other SeaFood Business articles discussing sea lice here.

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