"Air spawning'' may help steelhead
Friday, March 1, 2013
AHSAHKA, Idaho — The floor of the Dworshak National Fish Hatchery is normally an ugly mess on spawning day.
But an experimental effort to increase the survival of repeat spawning steelhead, which includes a different and friendlier egg collection method, is keeping it clean this spring.
Female steelhead are normally euthanized, bled and than sliced open to gain access to their eggs, which are then mixed with milt from males and incubated in the hatchery. The egg-spilling process leaves the floor bloody, slimy and slick.
Instead of killing and slicing the fish open, this spring hatchery workers are inserting needles similar to the type used to inflate basketballs into the abdomens of female steelhead. Compressed air is then pumped into their body cavities, forcing the fish to expel their eggs.
Afterward, hatchery workers “burp” or force the air out of the steelhead and revive them. The ones in the best physical condition are being placed in an experimental program run by the Nez Perce Tribe and Columbia River Inter-Tribal Fish Commission. The two entities are attempting to rehabilitate spawned-out wild female steelhead so they can spawn again and add to the recovery of the protected fish.
“We are working to recondition these hatchery steelhead to refine the techniques we use to recondition the wild steelhead,” said Becky Johnson, production director for the tribe’s fisheries division.
Steelhead are unique among Pacific salmon species. After spawning, a small percentage, known as kelts, can return to the ocean, feed, gain strength and repeat the process the following year, or in some cases after skipping a year.
In 1999, the tribal fish commission began reconditioning wild kelts in the Yakima River and started a similar program on the Snake River three years ago. Last year, the Yakima project saw a survival rate of 60 percent for kelts captured and rehabilitated.
Survival on the Snake River was much lower. Just nine of 144 wild kelts collected at Lower Granite Dam and rehabilitated at Dworshak Hatchery survived. Much of the mortality was related to a water supply problem at the hatchery, but officials are still interested in learning how to better care for the fish.
One of the big challenges is getting the fish to resume feeding. Adult steelhead don’t eat for the six months or so they spend in fresh water.
“Once we get them feeding they really take off,” said Scott Everett, a biologist with the Nez Perce Tribe and leader of the Snake River project.
He and Andy Pierce, a University of Idaho researcher employed by the tribal fish commission, said the hatchery kelts will allow them to experiment with different types of diets as well as treatments to deal with ailments such as fungus that grows on the scales of adult steelhead.
Pierce is interested in learning how to better identify when kelts are ready to spawn and if it is possible to determine if a particular fish is more likely to be a repeat spawner.
The hatchery kelts, which are not protected by the Endangered Species Act, give researchers like him more flexibility.
“If we need to kill the fish to see if the egg development is on track, we can do that with the hatchery fish and we can’t do it with the ESA-listed wild fish,” he said.
Officials at Dworshak are taking notice of the egg-gathering technique, known as air-spawning. Ray Jones, a fisheries biologists there, said the method is much cleaner. But that isn’t the only advantage. Jones said air-spawned fish could be returned to the river. Most generally survive at least a few weeks and others longer. Those fish would be available to anglers to catch. Some of them might be able to travel downstream to the ocean and eventually return as repeat spawners. Those that die would add nutrients to the river and help juvenile salmon and steelhead survive.
The hatchery is a popular place for school field trips and the public is welcome to view the spawning process. Jones said the air-spawning method also makes for friendlier viewing.