As the Elwha River restores itself after the removal of two fish-blocking dams, the Lower Elwha Klallam Tribe is studying how lamprey are using the new watershed.
“They’re poor swimmers, so they’ll swim along the banks of the river in undercut areas and hang out in logjams and rootwads,” said Rebecca Paradis, a project biologist heading up the study for the tribe. “They prefer dark spaces.”
The tribe set out 24 traps this spring to monitor lamprey populations in the river. The traps consist of three-foot-long PVC pipes with holes drilled in the sides. They’re placed along the banks of the river and in logjams in slow-moving water. The tribe’s screw traps in Little River and Indian Creek, tributaries of the Elwha, are also capturing post-spawning adults.
When caught, the lampreys are outfitted with radio tags and passive integrated transponder (PIT) tags so their migration patterns can be tracked by antennae in the lower 20 miles of the river. Antenna arrays are also located on Little River and Indian Creek, both tributaries to the Elwha.
“We want to see if any new lamprey come in and establish nests, and track their migration throughout the river, including where they spawn,” Paradis said.
While there were a handful of lamprey detected in the lower river before dam removal, there weren’t any above either dam prior to removal, she said.
Ammocoetes – larval lamprey, the size of a pen – were found in the tribe’s hatchery ponds in 2016. Mating lamprey can produce hundreds of thousands of eggs.
“Also, they are pheromone driven, so they don’t go back to their natural streams like salmon,” Paradis said. “There are so many unknowns.”
As larvae, lamprey are filter feeders, helping to preserve water quality for the marine ecosystem. As adults, they are parasitic on larger fish and marine mammals.
They have high oil content and are an energy-rich food for salmon, sea lions, seals and other marine species.
While they look like they belong to the eel family, they are more closely related to sharks and hagfish. Lamprey are considered the second oldest fish, next to hagfish.
After adult lamprey spawn and die, providing nutrients to the system much like spawned-out salmon.
- Three types of lamprey reside in the region: Pacific (Lampetra tridentate), river (Lampetra ayresi) and western brook (Lampetra richardsoni).
- The lamprey is very smooth and slimy to the touch. Its mouth is adapted for clinging and sucking.
- A lamprey has no true fins, jaws, or bones and can grow up to 30 inches in length and weigh more than a pound.
- Lamprey reside from Baja California to the Bering Sea
- Like a salmon, the Pacific and river lamprey are anadromous – it is born in freshwater streams, migrates to the ocean, and returns to fresh water as adults to spawn. Western brook lamprey spend their entire lives in freshwater.