No Simple Fisheries Fix

Finding a balance between native and popular introduced species remains a delicate art

A larms in the Southwest rang this week as anglers warned the National Park Service might be coming for brown trout on the Colorado River. The anglers’ wrath was directed at a proposal to protect and/or restore native fish by systematically electroshocking the 14-mile reach known as Lees Ferry to remove nonnatives.

Work to save native fish in the Colorado brings to mind those same efforts in the Flathead. While the particulars of the two systems are distinct, they are both vast, complex ecosystems with multiple native and nonnative fish competing for survival. In both cases controversial, multiagency efforts to restore native fish have run up against the reality that systems this vast and complex defy simple solutions.

Before dams, the Colorado earned its name. The river routinely ran thick with reddish silt, and warmed to bathtub temperatures in the summer. During the spring, when it seemed most of the topsoil of Utah and western Colorado was relocating itself to the Gulf of California, the river was a churning, roiling mess so thick the joke was that you could plow it.

Native fish adapted. The iconic humpback chub, the Quasimodo of the Canyon, has a pronounced ridge behind its head, which may help it hold to the river bottom during spring floods.

The dams changed all that. First Hoover, then Glen Canyon. Lees Ferry is the reach of river just downstream from Glen Canyon, which draws frigid water off the bottom of Lake Powell. Introduced rainbow trout thrived after the dam and a world-famous fishery was the result.

There are two other significant nonnative predators in the system: striped bass and smallmouth. Smallmouth bass have taken up residence where the Little Colorado River enters the big river. Water in the LCR — as folks in Arizona refer to it — is warmer and provides great smallmouth habitat. It’s also the last stronghold for spawning humpback chub in the Grand Canyon.

Brown trout at Lees Ferry probably migrated from Bright Angel Creek, where they were introduced in the early 1900s. Browns are probably found throughout the Grand Canyon now, but are not nearly as prolific as rainbows.

One suggested solution to the nonnative problem is installing a temperature control device on Glen Canyon Dam, allowing warmer water to flow through the Grand Canyon. Sounds great until you consider the striped bass fishery downstream in Lake Mead (managers didn’t think these anadromous salt water fish could reproduce in fresh water lakes, by the way. Oops). The frigid water in the upper river may act as a thermal barrier, however, preventing stripers from venturing too far upstream.

If you think chubs are running the gauntlet now avoiding smallmouth in the LCR, imagine hiding from rampaging bands of 50-pound stripers. In that scenario, humpback chubs would likely make a quick trip from endangered to extinct.

I value native fish and support how fisheries management has evolved from simply spreading game species around to managing ecosystems as a whole. My worry is that future management will be reduced to simply rearranging deck chairs on the Titanic of doomed species.

If I had a fisheries magic wand to use on the Flathead, I’d wave away the Mackinaw trout and mysis shrimp that tanked the epic bull trout fishery that once existed there. Still, I’d probably be inclined to keep one nonnative: Kokanee salmon.

Unfortunately there are no are magic wands, so finding a balance between native and popular introduced species remains a delicate art. Simple fixes such as electroshocking nonnatives out of existence will be neither delicate, nor, I suspect, effective.