Photo By Chief Petty Officer Matthew Cole | An incubation tray filled with steelhead eggs.The hatchery regulates the temperature...... read more read more
Just below Dworshak Dam, on the shore of the Clearwater River, lies the Dworshak National Fish Hatchery (DNFH). The DNFH raises millions of salmon and steelhead smolts every year to be released into the river and make their way down to the ocean.
“We are one of the largest steelhead facilities in the United States,” Jeremy Sommer, Nez Perce Tribe Hatchery Manager for the Dworshak National Fish Hatchery, said. “We work as a team to raise about 2.1 million B-run steelhead…. We also raise 1.65 million spring Chinook salmon that get released here. We also transfer another 400,000 juvenile Chinook to the Nez Perce Tribal Hatchery for grow-out to be released as smolts. The Nez Perce Tribe also raises Coho at the facility as part of the Coho Restoration Project.”
DNFH is owned by the U.S. Army Corps of Engineers and jointly managed by the Nez Perce Tribe and U.S. Fish and Wildlife. Historically, the B-run steelhead migrated up into the North Fork Clearwater River to spawn naturally. DNFH was constructed in the 1960s as a mitigation measure for the construction and operation of Dworshak Dam since these fish could no longer reach their natal spawning grounds. Now, every year, juvenile salmon and steelhead migrate out to the ocean from the hatchery in the spring and return 1 to 3 years later as adults.
The young fish imprint on the water they were raised on, allowing them to find their way back home as adults as they make the 500-mile journey back up the Columbia and Snake Rivers to the Clearwater River. From the Pacific Coast to the Clearwater River, these fish are essential to native tribe fisheries and the cultural and spiritual values of the tribes. They also provide opportunities for recreational anglers.
In the wild, fertilized eggs would lay in rocky streambeds until they hatched. At the hatchery, eggs and milt are collected from returning adult salmonids and the fertilized eggs are placed in incubation trays and kept in water from the Dworshak reservoir. The hatchery regulates the temperature and flow of water in the trays to keep the eggs healthy and growing at an appropriate rate.
“Water temperature controls how fast or how slow your fish are going to grow. If it’s cold, then they grow slowly. If it’s warm, they grow faster. We do a lot of water temperature manipulation here to make sure we get the full life that replicates, as best we can, nature to get the fish to the appropriate size when they’re supposed to leave,” Sommer said. “Eggs are taken typically for steelhead in January through April, and those eggs are raised and reared here about one solid year. We manipulate the growth of those eggs with temperature so the ones in April get just as big as the ones in January.”
When salmonids hatch, they do not need food right away. Newborn salmonids are known as alevin, or sac fry, because they are still attached to their yolk sacs. This yolk can sustain them for several weeks before it is completely absorbed into their bellies. The sac fry are kept in their incubation trays until then.
“Once the egg sac is absorbed, they look like there’s a zipper up their center. Once they’re ‘zipped up’ that’s when they get moved into the nursery,” Sommer said.
There are 124 tanks in the nursery, plenty of room for young salmonids, now called fry, to grow. Once in the nursery, the fry are old enough to be fed. However, at first, they are still very small, and must be fed accordingly.
“They will eat what we call Number Zero, which is a very fine dust-like feed. It is a balance of protein and fats and oils and vitamins,” Sommer said. As the fish grow, they are fed larger and larger pellets.
The nursery at the hatchery is a bio-secure area. This means hatchery staff must wash their hands and arms and wear raingear, including boots, that is only used in the nursery when attending to the young salmonids. All of this is done to prevent contaminants coming in from outside. Tanks are disinfected between batches of fry and supplied with flowing clean water from Dworshak Reservoir. The hatchery takes these precautions because young salmonids are more susceptible to diseases.
“We’re using reservoir water from above [Dworshak Dam]. This helps us manage around the disease IHNV [Infectious Hematopoietic Necrosis Virus] which has plagued the facility for years. We’ve managed pretty successfully for about a decade,” Mark Drobish, U.S. Fish and Wildlife Service Hatchery Manager for the Dworshak National Fish Hatchery, said.
IHNV is prevalent in returning adult salmonids, which shed the virus in the North Fork Clearwater River, the only water source for all outside rearing ponds until 2010. In 2010, plumbing changes allowed some of the Burrows Ponds to be supplied with reservoir water.
“These plumbing and operational changes are a credit to our partners across the river at the Clearwater State Fish Hatchery (Idaho Fish and Game),” Drobish said.
Once they graduate from the nursery, young steelhead are moved outside to Burrows Ponds, their final location before release. The Burrows Ponds give them even more room to grow as they transition from fry to smolt. They remain on reservoir water until they are 60 fish in a pound. By this point, they are “big enough to handle whatever diseases and pathogens are out there in the wild,” Sommer said.
Fish are moved into the ponds during the summer and stay there until the following spring. They are kept in river water and fed from demand feeders suspended above the ponds, which dispense food as the fish trigger the mechanism.
“It seems like a long process, but we get them up to 5.8 fish per pound. That’s our average target size for steelhead …. And at that point, they’re ready to hit the river and make their way down through the system all the way out to the ocean. They come back in a couple years and start the process all over again,” Jeremy Pike, a Biologist for the Nez Perce Tribe at the Dworshak National Fish Hatchery, said.
Hatchery releases at the Dworshak National Fish Hatchery typically take place in late March and into April. During this time, some steelhead smolts are trucked to different release sites, while others are released directly from the hatchery into the river.
“We raise about 2.1 million steelhead. Nine hundred thousand of those are trucked off-site. A couple hundred thousand of those typically go to Lolo Creek, 300,000 go to Clear Creek, and another 400,000 go to Red House, which is a release site on the South Fork of the Clearwater River,” Drobish said.
Over the years, the hatchery has established a rhythm to ensure that the fish are kept safe and healthy. However, it is not an easy job.
“There is a limited amount of water, so it is a puzzle here to keep the fish moving through the system and keep them growing at approximately the same speed to reach the same goal size,” Sommer said. “One of our biggest challenges is that this place was a technological marvel in its day, and it tends to break with all the different things that are used, the pumps, the screens, all the moving parts. And so, we have an elaborate alarm system and people that stand on call. We never know what’s going to happen. When it happens it’s always exciting and scary and we come out here and we defeat the challenge as a team.”
Another danger at the hatchery is maintaining oxygen levels in the water if the power ever goes out. The hatchery has backup generators; however, the hatchery still maintains constant vigilance to make sure everything runs smoothly.
“The salmon and the steelhead are very important to the culture of the Nez Perce people,” Sommer said. “We’re happy to be working with U.S. Fish and Wildlife and the Corps of Engineers and all our other partners to make this a success story.”
| Date Taken: | 04.11.2022 |
| Date Posted: | 06.22.2022 16:36 |
| Story ID: | 423547 |
| Location: | AHSAHKA, IDAHO, US |
| Web Views: | 82 |
| Downloads: | 0 |
This work, 4 million mouths to feed: Life at the Dworshak National Fish Hatchery, by Hannah Mitchell, identified by DVIDS, must comply with the restrictions shown on https://www.dvidshub.net/about/copyright.
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