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Settling a score with sea lamprey

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By most definitions, save that of another sea lamprey one presumes, they are a nasty piece of work.

“That’s pretty much it,” agreed Fisheries and Oceans Canada (DFO) Treatment Supervisor Shawn Robertson Friday morning inside the Sea Lamprey Control Centre’s mobile command/control centre along the shore of the Big Otter, adjacent to Otterville’s Treffry Mill.

A primitive eel or snake-like fish with leathery skin some 30-76 centimetres long in its parasitic adult phase, the sea lamprey’s dominant feature is a sucker-like mouth, filled with rows of sharp teeth surrounding a rasping tongue capable of penetrating other fish’s scales and skin. Native to the Atlantic Ocean, sea lampreys are believed to have spread through the Great Lakes via man-made shipping canals in the early 20th century. Their lifecycle from egg to adult takes on average, and based on location, between five and eight years to complete. A majority is spent on Great Lakes tributary streambeds in an eyeless worm-like larval stage, feeding on debris and algae. Following transformation into the adult parasitic phase, sea lampreys head (often around September) to their lake to spend 12 to 20 months feeding on fish, before returning to tributary streams to spawn.

Fastening to target fish via suction and teeth, adult sea lampreys drive a hole in their victims with their tongue, and secreting an anti-clotting agent, feed on blood and other body fluids.

“They drill a hole in the side of the fish,” said Robertson.

Fish which survive the initial attack are left with a gaping wound prone to infection, and it is estimated that under certain conditions, only one in seven targets ultimately make it. In its parasitic adult phase, one sea lamprey destroys an average of 18 kilograms of fish.

A catastrophic population explosion in the 1940s and 1950s, in conjunction with unsustainable fishing methods, had devastating effects on lake trout and whitefish populations.

Those fish are the main targets says Robertson, but sea lampreys will attack others including salmon.

“They are opportunistic, it something like that came by.”

Plummeting fish populations led to the Convention On Great Lakes, signed by Canada and The United States in 1954. The bilateral agreement affirms a need for the two signatory nations to cooperate to protect and perpetuate the Great Lakes sport, commercial and Aboriginal fisheries.

Fisheries and Oceans Canada (DFO) is the active agent north of the border, an effort led by the Sea Lamprey Control Centre in Sault Ste. Marie.

“It’s been going on ever since to help control the population of sea lamprey in the Great Lakes,” said Robertson. “Our program controls them, but it does not eradicate them.”

Totally eliminating the sea lamprey from the Great Lakes will be next to impossible scientists concede, but controlling the invasive pest during its larval phase has reduced the adult, parasitic population by as much as 90%.

Control methods include introducing sterilized male lampreys into tributaries, to compete with other males, ‘fire blanks’ and result in non-fertilized eggs during the spring (typically April and May) spawning run. Males do not return to the lake after spawning. The other major control method is hitting larvae in tributary streams with sea lamprey-specific pesticides including (most often) TFM (3triflouromethyl-4-nitrophenol).

“It is very effective, and has very little effect on non-target species,” said Robertson.

Literature provided by the DFO states agricultural irrigation must be ceased during and for 24 hours following treatment because exposure to lampricides may slow growth in some broadleaf plants, but potential effects on humans and other animals are marginal. The literature indicates a person would need to drink greater than 360 gallons of treated water at one time to produce harmful effects; laboratory studies suggest animals exposed to 500 times typical concentrations for an extended period showed no adverse effects; and that 95% of TFM residues are eliminated from fish one day after treatment, greater than 95% of residues are located in areas other than fish fillets, and additionally a person would have to consume more than seven tons of fillets from fish exposed to lampricides in one sitting to exhibit harmful effects.

Beginning Friday, a 20-member DFO crew was at the sharp end of the latter effort on – and very much in - the Big Otter Creek. Historically, control began at the base of the Rock’s Mills dam, but with its loss, the DFO mobile command and control centre was set up near the Otterville dam by the Treffry Mill.

“Since it has been removed, they have penetrated further,” said Robertson.

Lampricide was applied to the Big Otter and its tributaries last in 2009 said Robertson.

“It’s usually every three to four years.”

Essentially speaking, a carefully monitored dose of TFM is distributed into streams and their tributaries through hoses with strategically-placed holes. Downstream water is sampled and tested inside the unofficially named ‘chem truck’ to ensure proper application levels.

The effort proceeds in a timely and coordinated fashion downstream in an effort to completely ‘flush’ a stream of larvae. Larvae heading to shore to expire is a sign treatment has been effective.

Once begun in current low water conditions, the treatment will continue around the clock said Robertson, proceeding systematically in sections down the Big Otter and its tributaries, all the way to Port Burwell.

The team was operating along Jackson Line as of noon Sunday, and expected to approach Port Burwell by Monday morning. Application there will require more time due to deeper water Robertson said via cell phone, with the entire process, from Otterville on down, anticipated to take roughly a week.

“We should probably be done by Thursday,” he concluded.

With information courtesy of the DFO.

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