Anyone fly fishing the Big Wood River in the summer is unlikely to encounter the Wood River sculpin—even on sunny days when the stream bottom can be seen through the current.
Put on some snorkeling gear, however, and chances are you’ll spot the prehistoric fish darting between well-worn rocks and cobble.
With its froglike eyes, dirty brown patterning and fleshy lips, most would agree that the Wood River sculpin isn’t the prettiest of fish. But what valley residents may not know is the fish, endemic to the Wood River basin, faces an uncertain future.
“This species doesn’t occur anywhere else on earth,” says Don Zaroban, curator of fishes at the College of Idaho. “Once they’re gone, they’re gone. That’s concerning.”
Right off the bat, Zaroban—who has dedicated a lengthy portion of his career studying the Wood River sculpin—can name a few reasons why the fish was added to the “near threatened” category of the IUCN Red List in 2011.
“Their native range has contracted, by and large from irrigation projects. With Silver Creek being the sole exception, you probably won’t find it south of Highway 20,” he said. “Add in erosion, culverts and migration barriers at road crossings, and you have a lot of riparian habitat being lost. Their populations are fragmenting.”
Despite being the size of an hors d’oeuvre, Zaroban says, the Wood River sculpin requires ample living space in and around rocks and boulders.
“If you get a stream that’s sand-bottomed, you may see a few sculpin hiding in vegetation, but they truly need a cobble substrate to survive,” he said. “If you have a lot of runoff from streambank erosion, for example—the fish are going to bug out of there, because their living conditions are no longer right.”
Based on a fish census that Zaroban helped conduct, an estimated 800,000 Wood River sculpin resided in the Big Wood River two decades ago. Today, their population is unknown. The same goes for much of their life history, spawning behaviors and migration patterns.
To help uncover some of the mysteries shrouding freshwater sculpins in North America—a family that includes the Wood River sculpin—fisheries research biologist Michael Young is spearheading the Sculpin Qwest project at the U.S. Forest Service Rocky Mountain Research Station.
“The idea behind Sculpin Qwest was to use genetic tools to try and recognize the diversity of sculpins across the Rocky Mountain and Pacific Northwest regions,” Young said of the project, which kicked off in 2014.
Until last fall, ichthyologists across the West, including Zaroban, mailed thousands of sculpin tail clippings to Young for DNA analysis. (Tail clippings don’t harm sculpins, Young said—they’re actually prone to damaging that fin in the wild and can regrow it.)
“More important to sculpins are the pectoral fins up near the chest, which they use like a rudder on a plane to navigate up and down along the stream bottom,” he said.
From extracting DNA from the fin tissue of Wood River sculpins and sequencing it, Young realized that the fish is genetically closest to its even more imperiled cousin, the Shoshone sculpin.
“How the Shoshone sculpin has managed to persist in Idaho over the last 40,000 years, I have no idea,” he said. “Today, it’s limited to just a few springs.”
Idaho’s imperiled sculpins—the Wood River, Shoshone and Bear Lake sculpins—are hard to distinguish by sight.
“Even seasoned biologists can’t tell them apart, which is why we use genetic tools to resolve uncertainty,” Young said. “The best ichthyologists in North America agree that freshwater sculpins are just about the most difficult group of fish to physically identify.”
Similar to the common mottled sculpin, Idaho’s species are top-heavy, spending the bulk of their time resting on the river bottom like a tripod. Once an aquatic insect comes into sight, the fish will dart out in quick spurts, careful to avoid predators coming from above—“herons, water snakes and biologists,” Zaroban says.
Rainbow and brown trout also take an occasional liking to Wood River sculpins.
“Whenever you’re in trout or salmon stream, you’re almost always also in sculpin stream, and that goes for the Big Wood River,” Zaroban said.
Though the dynamic between native trout and Wood River sculpin remains unclear, Zaroban suspects hatchery trout “aren’t helpful” to the sculpin’s survival and may add another layer of competition.
“Native species have had tens of thousands of years to work out relationships with one another, so whatever they were going to do to one another has long been settled,” he said. “When you throw in hatchery fish, it’s just that many more hungry mouths to feed.”
In the next few years, Zaroban hopes to investigate the migration patterns of Wood River sculpin at Gladiator Creek near Galena Lodge—a project he’s proposed since 2006.
“I think they move around more than we know,” he said.
The project would entail injecting a computer chip into the body cavity, releasing the fish and tracking them with solar-powered antennas positioned along the creek.
“That way, you get to see who’s coming and going,” he said. “It’s an expensive proposition—the study would probably cost over $100,000—but it could be done with support from the BLM, The Nature Conservancy and the National Science Foundation.”
After retiring from the Idaho Department of Environmental Quality, Zaroban—also the co-author of “Fishes of Idaho: A Natural History Survey”—says he looks forward to dedicating more time to the Wood River sculpin.
“I’m really interested if they’re able to swim upstream and downstream through corrugated road tubes,” he said. “There are so many questions to be answered.”
Zaroban said he’s hopeful that his tracking project will receive funding. After all, he said, Wood River Valley residents tend to be conservation-minded, and his dissertation research on the Wood River sculpin over a decade ago was met with “overwhelming support.”
“Out of 400 riverfront properties that my team needed to access, only one homeowner very politely turned us down,” he said. “That was amazing to see, especially in Idaho.”