Researchers focus on helping lowly lamprey
Raising the fish in hatcheries might be solution
Thursday, April 21, 2011
The life cycle of the Pacific lamprey
After arriving from the ocean, lamprey spend a winter in fresh water.
Building their nests in gravel, they swish out a depression and then use their suction mouths to move stones into position as a small wall against the current.
Their nest prepared, the lamprey begin their rather bizarre mating ritual. The male grasps the female’s head with his suction mouth, and the pair twirl around one another in a passionate embrace, expelling the milt and pepper-size eggs into the nest. The adults then die, their bodies providing nutrients for the river’s food web. Two to three weeks later, the eggs hatch.
These 5- to 10-millimeter hatchlings, or ammocoetes, drift blindly in the current. The ones lucky enough to survive wriggle down into sediment rich in organic material and algae. They stay in the river bottom for three to seven years.
No one is sure what the cues are, but the young lamprey eventually emerge from their muddy cocoon with a yearning for the ocean. The ones that make it past the dive-bombing birds, salmon and other predators live for the next one to four years in the ocean. Once prey, they become predators.
Lampreys have been discovered attached to salmon and even whales, latching on with their suction mouths.
Using three interior teeth and a sandpaper-rough tongue to break through the skin, the ocean-going lamprey feed on their prey’s interior fluids and then detach when they’ve had their fill.
— Erik Robinson
PORTLAND — Lamprey may lack the iconic status of Northwest salmon, but the eel-like jawless fish is no less important to tribal culture.
Alarmed by their dwindling populations, the Columbia River Inter-Tribal Fish Commission this week is hosting an international forum exploring the causes of their decline and how to revive them. Dams impede lamprey migration, pollutants mar the sediment where they rear, and their prey in the ocean may be thinning with overfishing and a changing climate.
None of these issues will be easy to reverse, so researchers are beginning to suggest a familiar solution:
Why not raise them in hatcheries?
Scientists from the Pacific Northwest joined researchers in Japan and Finland during the forum at the Doubletree Hotel near the Lloyd Center. Researchers compared notes about experimenting with artificial propagation and talked about the potential for supplementing wild lamprey populations with those raised in hatcheries.
Yet even supporters see it as a stopgap measure.
“We’re down to such low numbers, and we don’t have the resources we need to deal with (dam) passage issues,” said Bob Heinith, hydro program coordinator for the commission. “We just feel like this is one of the tools in the tool box we have to promote.”
Raising lamprey in hatcheries is not a new concept, although it has yet to be tried on a large scale.
U.S. Fish & Wildlife Service researchers suggested, in a 2007 study, raising hatchery larvae in a pollution-abatement ponds at a federal salmon hatchery in Entiat, north of Wenatchee. Abatement ponds are commonly used in hatcheries to collect wastewater — full of fecal material and uneaten food — from raceways, holding ponds and tanks. It also creates a thick mat of organic material that happens to be well-suited for filter-feeding lamprey larvae, known as ammocoetes. The ponds could provide a safe head start for larvae, before outplanting them to rivers and streams, the researchers suggested.
“Seeding larvae into this predator-free and nutrient-rich environment could produce high survival of lamprey, and the homing of returning adults to this ‘natal’ stream could re-establish a spawning population,” according to the report authored by fish biologists Mark C. Nelson and R.D. Nelle.
Heinith said an artificial propagation program for lamprey shouldn’t be expensive because they could be raised in existing salmon hatcheries.
“Lamprey are pretty easy compared with salmon,” he said.
David Close, a member of the Confederated Tribes of the Umatilla Indian Reservation and a fisheries professor at the University of British Columbia, isn’t convinced that artificially propagating lamprey will work any better than it has for wild native salmon.
That’s because habitat destruction, overfishing of prey species, pollution and a changing climate continue to create long-term challenges.
“We never seem to address the real causes,” Close said.