When Electricity and Water Do Mix: Electrofishing to Preserve the Westslope Cutthroat Trout of Red Butte Creek



Hunched under a battery and generator heavy on her back, Beth Gardner squeezed a switch, instantly transmitting 800 volts from the probe in her hand to the waters of Red Butte Creek. The boxed apparatus beeped with the insistence of a paramedic’s AED, but as she scanned and shocked each riffle and pool, Beth didn’t flinch. At least not until a white shape surfaced in the swift creek’s froth, and she started yelling hysterically, “there’s one, right there, yes…you got it!” Graham plunged his net and scooped the quarry to find it a fish with a dark back and a black, worm-like black pattern. “Bad guy,” Graham said, proudly and carefully dropping the brook trout in a few inches of water at the bottom of a five-gallon bucket to revive.

It’s not that they’re bad, but as the Fisheries Biologist for the Flathead National Forest, Beth Gardner is charged to conserve the native fish that evolved with this place. That’s why she recruited a crew of Forest Service staffers and me to help with electrofishing, a novel method used to census the piscine realm. The Forest Service partners with SVC to monitor the Swan Valley’s “con pop” (i.e. conservation population) streams, which are so designated for their critical importance to westslope cutthroat trout. The iconic cutthroats – Montana’s state fish – have a stronghold in the Swan Valley’s clean, frigid creeks, but even here they face habitat pressures ranging from erosion to road sediment to culverts and other forms of fragmentation. The impacts of non-native fish are also of serious concern for cutthroats, especially in the ways hybridization with rainbow trout dilutes their genetics, and how predation from brook trout leaves them, well, gone. 

Con Pop streams like Red Butte Creek are special because the habitat is good, the cutthroats are purebreds, the rainbows none, and the brookies few. In cases like these, where the creeks cross Forest Service land, Gardner has made difficult management decisions to protect these qualities. In the tradeoff between invasion and isolation, Gardner has sometimes chosen the latter, protecting the cutthroats from non-native invaders with a concrete barrier that denies fish but not flow. A lot goes into the timing and placement of these structures, and Red Butte Creek's barrier required intensive observations of each fish population’s extent, the history and patterns of the creek’s flow, and the degree of purity in the cutthroat’s DNA. In its aim to cleave the species, a barrier preserves cutthroats with pure genes in pristine habitat, a combination which is increasingly rare today.

That's the theory. In practice, we still have a lot to learn about the effect of such barriers, and their installation does not mean the work is over. In fact, a barrier sparks the urgent need to make sure all brookies and rainbows are below the structure as intended. That's where electrofishing comes in, which has evolved a lot since 1875 – four years before Thomas Edison flicked on the first light bulb – when researchers began to describe the effect of electric current on the movement and orientation of fish. Experimentation continued in and out of the lab, and soon after World War II, Alabamans had even scrapped together a way to “phone catfish” by shocking the bottom dwellers with the magneto component of crank style telephones. The practice has become more effective and safe in the decades since, but the basic premise remains: stick an electrified probe upstream in the water, which thereby stuns any large-bodied creature (fish) caught between the probe and a wire loosed downstream out of the generator; the temporarily stunned fish float to the surface; alert netters scramble about like lacrosse players eager to capture the fish for the bucketeer before it floats away. While recreational and commercial uses of electrofishing are discouraged – and in some places, illegal – the technique has become quite effective among scientists, esoteric as it is. 

When done properly, the electricity leaves the fish stunned but not hurt. With rubber waders on our legs and plastic handles on our nets, we didn’t feel it all, and because the power conducts best over large skin surface areas, the charge does not register with most aquatic insects or Rocky Mountain tailed frogs, which share the trout's turbulent home. Soon after getting zapped, a stunned fish's fins start twitching, and before long they're churning the revival bucket on par with the creek they long to return to. Each cutthroat earns that homecoming soon after recovery, but brookies must wait until day's end, when they’re trucked back downstream, and plopped below the barrier. 

A   westslope   cutthroat trout – distinguished by a red slash on its throat and spots on the upper,   tailward   parts of its body – enters the revival bucket.

A westslope cutthroat trout – distinguished by a red slash on its throat and spots on the upper, tailward parts of its body – enters the revival bucket.


Climbing over root wads, skirting deep pools, and traversing slick cobbles – with sloshing buckets of fish, nets, and an electric backpack – makes for slow work, and half-a-mile per six hours is a good day. But every pool and riffle had us asking: is this the end of the brookies? Once, as we caught a small brookie, I thought its diminution a sign of the invaders petering out.  But I was wrong. It was only an "age zero fish", just born this year and only able to drift downstream, below where his parents had the strength to fight against the current. Within the hour, we did find two adult brookies who very well could’ve been the young one’s parents. It's not every day we consider not the species, distribution, and demographics of fish in our creeks, but this is the type of underwater wonder that electrofishing provokes. Each question is answered with a question, but after catching 76 cutthroats and 12 brookies, we were glad to have gone below the surface.

Backgrounded by a storm over the Swan Range, the electrofishing crew   is all smiles   after a day on Red Butte Creek.

Backgrounded by a storm over the Swan Range, the electrofishing crew is all smiles after a day on Red Butte Creek.