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Aquacultured | Pt. 2

By: | May 9, 2011

Fishers and aquaculturalists get to the bottom of pesticide concerns

Gavin Simms

(Read Part 1)

Sea lice may be natural parasites in the open ocean, but upon attaching themselves to farmed fish reared in cages, they become a fast-spreading pest.

The single-most pressing issue facing salmon farmers today, sea lice feed on fish skin, mucus and blood, and untreated infestations can lead to death. They thrive in warmer temperatures; a major reason why Newfoundland’s cool coastal waters have become a hot spot for farmers from away.

“Certainly, from an environmental impact perspective, it is a much more favourable one that we would like to use. No one likes to use anything that would be considered a pesticide.” —Miranda Prior

“With our waters being colder, we haven’t had as high a problem with sea lice in the past as they’ve had in other regions where the water could be warmer,” says Miranda Prior, Executive Director of NAIA. “We don’t have the issues that New Brunswick ran into last year.”

However, aquaculture farms on the south coast do experience a peak in cases of sea lice in the late summer/early fall months, when the ocean is at its warmest. Prior says they’re currently investigating a variety of treatments to help deal with the problem, instead of relying on just one.

Learning from mistakes of their mainland neighbours, the plan is to avoid falling into the same trap as many NB farmers whose fish stocks built a resistance to frequently used treatment, SLICE.

SLICE and Salmosan

SLICE is an in-food drug treatment containing emamectin benzoate (belonging to a class of chemicals called avermectin which are poisons affecting nerve cells). Upon digestion, the drug passes through the lining of the fish’s gut and into its tissues, where it is then absorbed by sea lice attached to the fish.

It is also the number one treatment being used to fight sea lice in N.L. right now.

The first of two possible treatments N.L. farmers might find themselves applying in the near future is Salmosan (a widely debated bathing pesticide containing azamethiphos that is applied directly to the water in tarped cages or used in wellboats).

Hydrogen Peroxide

Prior says a wellboat will be headed for our shores in the summer so hydrogen peroxide can be put to use removing sea lice from the skin of farmed salmon. The chemical requires the fish be pumped into the belly of a wellboat containing it, and back again — keeping the treatment out of the ocean entirely.

“Certainly, from an environmental impact perspective, it is a much more favourable one that we would like to use,” says Prior. “No one likes to use anything that would be considered a pesticide.”

But, the problem with the wellboats, from an operating perspective, is they’re expensive to make use of.

“To ensure that all farmers can access it, it may be difficult,” Prior says, “because you’ve got some small farmers as well. It may be something that’s limited to larger companies or contracted to the smaller companies.”

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