The following is courtesy of the U.S. Fish and Wildlife Service Pacific Southwest Region:
California may have experienced record rainfalls this past winter, but negative impacts due to the unprecedented five-year statewide drought continue for Chinook salmon produced at the Coleman National Fish Hatchery.
In a unique partnership that hasn’t been utilized in 40 years, the state of California has stepped in to help out.
The Coleman hatchery, located in Anderson, California is the only federally operated fish hatchery in the state with an annual production of 12 million fall-run salmon smolts that are typically released into nearby Battle Creek each spring. This allows them to complete the imprinting cycle during their outmigration to the ocean.
In 2014 and 2015 however, due to extreme drought conditions which prevented release into Battle Creek, most of those 24 million fish were driven almost 200 miles by truck (about 280 river miles) and released into locations near the San Francisco Bay, including Rio Vista, Mare Island and San Pablo Bay.
As a result, a good portion of the Chinook salmon smolts that were released in 2014 – about 8 million of the 12 million were trucked that year — strayed off course when they returned to freshwater to spawn. In 2015, poor conditions persisted and all 12 million of those smolts ended up being trucked. These fish are returning to spawn primarily during the current year.
California Department of Fish and Wildlife’s Nimbus Hatchery, located near Sacramento on the American River, opened its fish ladder early on Oct. 9 to accommodate the arrival of those straying fish. Beginning Oct. 10, twice a week, on Mondays and Thursdays, hatchery workers from Coleman arrived in Sacramento to help CDFW spawn fish that originated in Battle Creek.
The eggs collected at Nimbus will be returned to Coleman to prepare for the planned spring release, to help augment what could be the lowest Chinook salmon return ever, said Brett Galyean, project leader for the Coleman hatchery complex.
In typical years, Coleman will see a return of around 30,000 fish and since 1996, as many as almost 143,000.
This year, however because of the drought-caused trucking, only about 3,000 are expected to return to Battle Creek.
“It’s pretty spectacular the way the state has stepped up to help us out,” said Galyean, adding that the last time Nimbus and Coleman hatcheries worked together in a similar fashion was in the late 1970s. “I’ve never seen anyone open their fish ladder three weeks early before and we really appreciate it. It’s definitely not normal operating procedure for them.”
Before release, Coleman marks 25 percent of its salmon by clipping off the adipose fin—the small, fleshy fin on the fish’s back between the dorsal and caudal fins. These clipped salmon also have coded wire tags the size of pencil lead, inserted into their nose. Under a microscope, biologists can read the code etched on the tag to determine where and when the fish was hatched, and where it was released.
Fall-run Chinook from Battle Creek live three to four years and typically spawn in October and early November, compared to fish from the American River that spawn in November and early December.
When the salmon reach the Nimbus Hatchery, staff then separate the fish that have had their adipose fin removed, indicating that they carry the tiny coded tag. Fish identified as being of Coleman origin will be spawned with one another, and their fertilized eggs returned to Coleman. Fish that have not had their adipose fin removed will be spawned and their eggs will be reserved, ready to be used to meet Coleman’s production goals.
Those fish that are not yet ready to spawn will have a colored tag attached to their dorsal fin and will be returned to the American River, where they will be available to anglers until they either spawn naturally or climb the ladder again to spawn at the Nimbus hatchery.
Marc Provencher, a fish biologist at Coleman for eight years, has been working out of Nimbus most Thursdays during the collection process, collecting eggs from the females and milt from the males that will be mixed with the eggs to fertilize them.
“Today was probably the best day we’ve had,” said Provencher, while on his way back to Coleman on Oct. 26, noting they had collected 140 fish that day.
“We’ve collected close to a million eggs since we started this. Every one of them helps,” he said.
“We’ll be working at Nimbus until the marked fish stop showing up; probably in early November,” Galyean said.
Coleman’s production goal is to collect roughly 14 million eggs at the hatchery, Galyean said.
Each spawning fish produces about 5,300 eggs on average, and about 190 spawning pairs have been collected so far from Nimbus.
The operation at Nimbus ended Nov. 1, and both hatcheries will continue with their fall spawning public viewing schedules with Nimbus returning to its normal Monday-Thursday schedule through mid-December.
Coleman is open to public viewing Tuesdays and Thursdays, 8 a.m. to noon, through mid-November.