Scientists release kokanee fry to re-establish species
April 13, 2010
By Warren Kagarise
On a rain-soaked night late last month, scientists gathered along the banks of Ebright Creek to complete the latest step in a monthslong experiment meant to pull a species from the edge of extinction.
The team used buckets to transfer Lake Sammamish kokanee salmon fry — a few millimeters long and not much larger than a paperclip — from aerated coolers for the last leg of the journey from a hatchery to the wild.
Months earlier, biologists and ecologists collected mature kokanee from the same creek, as part of a last-ditch effort to boost the population of the dwindling species. From Ebright, Lewis and Laughing Jacobs creeks, teams took the fish to the Issaquah Salmon Hatchery, where teams harvested almost 35,000 eggs.
Scientists had not attempted to raise Lake Sammamish kokanee at a hatchery before. Throughout fall and winter, workers at the state hatcheries in Ravensdale and Lakewood raised the fry from fluorescent orange eggs.
Hans Berge, a King County senior ecologist, and a team gathered March 25 to release about 14,000 fry into the same creeks where he and others netted spawning salmon last fall. In a reverse maneuver, the team plunked the fledgling kokanee into the creeks on a cloudy, wet night.
The nighttime release offered less risk of predators picking off the fry.
Scientists deposited the fry far upstream from Lake Sammamish to allow the fish time to “imprint” on the creeks. Biologists hope the fry memorize the characteristics of the waterways and someday return to the creeks as stop-sign-red, mature salmon to spawn.
Berge estimates the fry swam from the creeks into the lake on the same night as the release. Inside Lake Sammamish, the fry feed on microscopic organisms called zooplankton. Only a fraction of the fry will reach maturity and — in three or four years — return to the creeks to spawn.
Within the next few weeks, scientists will release another 20,000 kokanee fry into Ebright, Lewis and Laughing Jacobs creeks.
Cory Cuthbertson, a fish hatchery specialist at the Cedar River Hatchery in Ravensdale, said scientists released the fry in Issaquah about a month after the tiny fish emerged and started to feed. Hatchery workers marked the fish by adjusting water temperature to alter the otolith — a tiny bone inside the ear.
The characteristic will allow scientists to differentiate between hatchery-spawned and wild salmon, as part of a program to re-establish kokanee in Lake Sammamish.
The salmon species claims sockeye as a close relative, but the smaller kokanee live in landlocked bodies of water.
Berge said although the official tally does not yet exist for last year, teams counted about 1,100 spawning kokanee throughout the tributary creeks.
Environmental groups, local governments and the Snoqualmie Tribe petitioned in 2007 to list Lake Sammamish kokanee as endangered. The federal government has yet to decide on the request.
If the government declares a species as endangered, the listing requires officials to develop a recovery plan, designate critical habitat and put penalties in place for people caught harming the fish or habitat. Measures to preserve kokanee could change how development proceeds upstream from Lake Sammamish.
Kokanee used to thrive in Lake Sammamish. The species formed the foundation of a robust ecosystem and a recreational fishery. Snoqualmies fished for the plentiful salmon, a staple food.
The kokanee population shrunk due to habitat loss and other factors still under investigation. Scientists said other possible causes for the decline could be changes in how the tributary streams flow — as a result of development near the banks — predation or water quality.
But the plan hatched to collect mature salmon, harvest eggs and introduce kokanee fry into the creeks near Lake Sammamish also carried risks.
Scientists passed the initial test during the harvest last fall.
Removing a salmon from spawning grounds can kill the fish. Changes in temperature and water quality stress the salmon and makes them more susceptible to disease and infections. The shock can also cause female kokanee to dump eggs inside the buckets used by scientists to transfer the fish.
Teams at the Issaquah hatchery collected the eggs, and then shipped the precious cargo to other state hatcheries. Scientists picked the Ravensdale and Lakewood sockeye hatcheries because of the characteristics the species share. The dual-hatchery approach allowed for a backup — in case the experiment failed at the other hatchery.
Because Lake Sammamish kokanee had not been raised in a hatchery before, biologists faced basic-but-fundamental questions related to water temperature and quality, and what to feed the tiny fish. In the end, the hatcheries treated the kokanee similar to sockeye — and the effort worked.
The dwindling numbers allowed scientists to experiment with ways to increase the kokanee population. Berge said scientists plan to collect some salmon during the next kokanee run, although no details had been finalized.
“If push comes to shove, I think we could step in here to help,” he said.
Warren Kagarise: 392-6434, ext. 234, or firstname.lastname@example.org. Comment at www.issaquahpress.com.