POWELL — Launching into a hot chocolate-colored river, a three-man team began its final search of the spring for a survivor from the Jurassic period.
One shift away from finishing a five-year study, the crew cast off into the fast-flowing river hoping to capture a record amount of shovelnose sturgeon. They were looking to track the progress of a reintroduction project that began more than two decades ago.
In 1996, Wyoming Game and Fish Department biologists stocked sturgeon in the Bighorn River in an attempt to create a unique sport fishing opportunity for anglers and to return the species to one of its native habitats. Looking at the fish leaves no doubt that this is an ancient species.
“It’s a dinosaur,” said Cody Region fisheries biologist Joe Skorupski.
For the past four years, Skorupski has spent countless hours battling the elements on the river. In spring and early summer, the rush of snow melt carries sediment, causing the river to muddy.
“Since the start of this project we’ve had high water years, big water years,” Skorupski said.
Two technicians, Jake Ruthven and Colton Webb, stood at the bow. Each time they detected the sound of a tiny transmitter carried by the fish, a long net was deployed.
Sometimes the nets returned full of sauger, common carp, redhorse and large chubs. But when conditions were right, the nets would come back full of the underwater dinosaurs — sometimes as many as six to eight at a time.
“Keep them coming. I’m looking for a record day,” Skorupski said as the nets finally revealed multiple sturgeon.
The fish were quickly moved to a large livewell. Each individual was measured, weighed, tagged twice, tested for sex and maturity, and then gently released unharmed back to the river.
When a female was caught, Skorupski tested for eggs by carefully inserting a tube attached to a syringe into their bellies. On this day, there were very few signs of females ready to spawn.
It’s not easy to gauge success with the species, which starts its life in a free fall. Eggs hatch after a few days, then the embryos sink to the bottom of the river and drift with the current. Depending on temperature and the river’s flow, the embryos will mature into larvae. Only then will they begin to swim.
Their lifecycle in the Bighorn River is complicated by Yellowtail Dam in southern Montana. Sturgeon embryos need between 60 and 150 miles of drift to mature into the larval stage before hitting Bighorn Lake. In fast water years, the embryos may reach the reservoir too soon.
Fast water also makes it hard for adults to successfully spawn — and makes it impossible for the Game and Fish team to capture sturgeon in embryonic stages for modeling data.
“We haven’t got our hands on any embryos, mostly due to high waters,” Skorupski said.
As a result, he’s unable to say definitively that the species is naturally reproducing in the Bighorn.
Radio telemetry transmitters deployed in 2015 and 2016 are now near the end of their battery life and soon will go silent. But just because the five-year study is over doesn’t mean sturgeon are on their own, Skorupski said.
“We’re going to build in monitoring on a multiyear rotation,” he said. “One of the advantages is we can continue to tag individuals for long-term monitoring because they live so long.”
This was the first year of the study that not a single female was found to be exhibiting the tell-tale signs of being ripe for spawning. However, the team tagged 50 sturgeon.
The study shows the river has a “fairly robust population” with sturgeon of different age groups, Skorupski said.
Anglers can enjoy the fruits of Game and Fish’s labor on the Bighorn River. Sturgeon can be caught on the same type of bait as catfish — insects such as worms and leeches.
Game and Fish plans to continue stocking sturgeon through 2020 and then will reevaluate the program.