Biologists have giant questions about monster fish in upper Snake River
Mon., Nov. 1, 2021
Blood is drawn from a Snake River white sturgeon below Minidoka Dam this summer as part of a study. ((Courtesy of Idaho Fish and Game))
IDAHO FALLS – Even though sturgeon have been around unchanged for more than 200 million years, knowledge of the relative newcomer now patrolling the upper Snake River of eastern Idaho is a big question mark.
Idaho Fish and Game has been dropping hundreds of white sturgeon into the Snake River between Idaho Falls and the American Falls Dam for the past 30 years but has never paused to take a look at what’s going on with the fish that is not native to the river above Shoshone Falls.
This summer, fisheries biologists decided to take a peek to see if it was worth a deeper study. First looks proved to be an eye-opener.
“We did find out that it is a more robust fishery than we thought,” said Joe Thiessen, regional fisheries biologist and lead on the study. “There’s a lot of fish there. We did find out that growth rates were higher than what we’ve seen in our more wild, historic sturgeon populations, say in like Hell’s Canyon, and in and below Bliss Dam. That’s encouraging to see that they’re growing fast.”
Sturgeon can live to be more than 100 years old, grow to 10 to 12 feet long, weigh more than 200 pounds and don’t spawn until they’re 20 years old. For those reasons – and because Snake River sturgeon have been blocked from migrating to traditional spawning areas by dams – sturgeon fishing in Idaho is catch-and-release only with specific gear regulations to protect the fish. It is illegal to remove a sturgeon from the water.
IDFG’s summer survey collected 116 sturgeon from Milner Dam upstream to Idaho Falls. Fish ranged in size from 2 feet to 8 feet long. After initial findings, Fish and Game decided to dig deeper to study the population and collaborate with the University of Idaho over the next two years.
“Ultimately, this work will help develop management strategies to sustain and improve opportunity to catch these amazing fish,” Fish and Game’s Terry Thompson said in a statement.
Pat Kennedy, fisheries biologist in Idaho Falls, said the summer study reached up to the power plant just below the falls in downtown Idaho Falls.
Hot spots for sturgeon in the upper Snake River include areas below dams, such as the Gem Lake Dam and in particular, the American Falls Dam. Kennedy said the dams have deep pools that are the type of habitat sturgeon prefer.
Although sturgeon are native to the Columbia and Snake rivers, dams cut off the fish from spawning waters. Fish and Game began supplementing their numbers with hatchery sturgeon. In years when hatchery goals are exceeded, excess sturgeon are stocked above Shoshone Falls. This practice began in 1989.
Thiessen estimates that since 1989 about 7,000 sturgeon have been stocked above Shoshone Falls.
Traditional sturgeon fisheries in the state include the Snake River downstream from Shoshone Falls, and the Kootenai and Salmon rivers. CJ Strike Reservoir on the Snake River southwest of Mountain Home is one of the state’s top sturgeon fisheries.
“We hadn’t done any hard looks to where fish were moving once released, if they were surviving, catch rates from anglers, where anglers were catching them,” Thiessen said. “We kind of heard through anglers that there was a sturgeon fishery from that stocking. We didn’t exactly know what type of fishery it was or how good it was.”
Thiessen said the new study will take blood samples, look at genetic makeup, growth rates and survival. Stocked fish all have PIT tags to help track the fish.
“We found that they are moving quite a bit, upward of 5 miles downstream generally from their stocking location,” Thiessen said. “They are successfully passing through dams. A lot of them passed through four major dams.”
He said he believed the fish passed through the dams’ radial gates during the spring, rather than through deadly hydroelectric turbines.
“None of the upper Snake River dams have fish ladders because we don’t have any anadromous fish above Hell’s Canyon,” Thiessen said.
Summer studies found that sturgeon stocked near Idaho Falls were less likely to move downstream than those at American Falls.
Because several younger sturgeon have been found without PIT tags, the question has been raised if the fish have been spawning naturally.
Kennedy said sturgeon stocking in Idaho Falls began in 2007 and have been stocked most years since then.
“I suspect that we do have natural production,” Kennedy said.
He said his son salvaged a juvenile fish from a lava pool next to the river that had neither a tag or other markings indicating it was a stocked fish.
“There’s some evidence that might suggest it,” Thiessen said, “but right now we’re not 100%. There’s no silver bullet evidence.”
He said he knows that sometimes hatchery-raised fish shed their PIT tag.
Thiessen said the question of one day harvesting sturgeon, even on a limited basis, can’t be answered until they understand the nature of the population.
In the meantime, several diehard sturgeon anglers are busy promoting the fishery in the upper Snake River.
“There’s a fun, rowdy, and hard fishing group of local anglers and guides who aren’t bashful about sharing exactly how much they love sturgeon and the fishing opportunity they provide,” Thiessen said. “These same people were very instrumental in helping us find, and in many cases, collecting sturgeon for this study.”
American Falls-based fishing guide Brett Jones said one threat he has seen to the sturgeon fishery is anglers not abiding to gear regulations. Using too light of tackle on sturgeon forces anglers to play the fish to exhaustion and is likely to kill the fish, he said.
“If you fight a sturgeon for over an hour, then that sturgeon will be fighting for its life when it is finished,” he said. “That lactic acid build up will kill them.”
He often finds illegal barbed hooks and lighter tackle still clinging to sturgeon he catches, Jones said. Heavier tackle can be had for less. than $200, he said.
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