The Lake Chub

by Doug Backlund

Click here for photo

We were continually looking for trout in these streams, which seemed as though made expressly for that fish, which requires an unfailing flow of cold pure water. There could be no finer trout streams in the world than these were they once stocked. As it was, we found nothing but some small chub, and a species of sucker of perhaps a pound weight.

--William Ludlow, Brevet Lieutenant Colonel, U.S. Army, in "Report of a Reconnaissance of the Black Hills of Dakota made in the Summer of 1874" (Custer Expedition).

Although known today for its excellent trout fisheries, the streams of the Black Hills historically had few fish species and no trout. Historical records of Black Hills fish are scarce, but based on available information, only four species of fish are thought to be native to the streams of the higher portions of the Black Hills. One of these species is the lake chub, probably the same chub reported by the Custer Expedition of 1874. The lake chub was once abundant in the Black Hills, where it was reported to be common as late as 1962.

The lake chub is one of hundreds of species belonging to the minnow family, one of the largest of all fish families. The lake chub is a northern fish and is common in the northern Rockies, most of Canada west of Hudson Bay, and in the Yukon River system of Alaska.

The Black Hills population is considered a relict of the glacial periods. Other relict populations, stranded in isolated habitats, are known in North Dakota, Nebraska, Colorado, and Iowa. Although the lake chub tolerates a wide variety of habitats, it prefers cool streams and lakes. Lake chubs can be extremely abundant in good habitat and often form large schools. It is an important forage fish in large northern lakes that often contain few other species of forage fish.

Like most minnows, the lake chub is a small fish, rarely attaining a length of more than six inches. Adults are dark brown to green above and pale below, with a dusky lateral stripe that varies from a very distinct marking to an inconspicuous line. Breeding males develop tubercles on the head and the pectoral fin. In addition to the development of tubercles, males also display reddish-orange spots at the base of the pectoral fin and just behind the gill cover. Lake chubs have large eyes and a rounded barbel situated on but not quite at the end of the upper jaw.

Lake chubs are mostly carnivorous, feeding on aquatic insects and small crustaceans. In lakes and streams with few other small minnow species, lake chubs are an important link in the food web. By feeding on small organisms that are not available to larger fish and fish-eating birds and mammals, lake chubs channel food energy to these larger animals in many northern lakes and streams.

Just how lake chubs found their way to the Black Hills is open to debate. Possibly, the species was once more common and widespread during the cooler glacial periods of the Pleistocene. As the climate changed, lake chubs could no longer survive in the warmer prairie streams and rivers but were able to thrive in cool Black Hills streams.

Another intriguing possibility involves a geological process known as stream capture. Lake chubs are also known from the Little Missouri River, which now originates in northeastern Wyoming. Long ago, the Little Missouri River lost about 110 miles of its length to the Belle Fourche River. The evidence of this stream piracy is shown in part by the abrupt change in direction of the Belle Fourche River northwest of Colony, Wyoming.

A flat valley extends from this point to the northwest about six miles to the Little Missouri River. When the eroding headwaters of the Belle Fourche River reached the Little Missouri River, the upper part of that stream was acquired by the Belle Fourche River and the aquatic inhabitants of the Little Missouri gained access to the Belle Fourche and Cheyenne rivers and the Black Hills. Several other fish species may have found their way to the Black Hills as a result of this geological event.

The future of the lake chub in the Black Hills is bleak. This species has not been reported from the Black Hills for many years and may to be extirpated. Why did the lake chub decline so drastically in the Black Hills? Some biologists point to the introduction of trout, which may prey on the lake chub. However, the lake chub is a species that evolved with predation, and a healthy population should have been able to withstand the presence of trout.

The introduction of exotic fish may have been a secondary factor, but a more likely primary cause is the decline of Black Hills streams and streamside vegetation since the settlement of the area. Stream flows have been reduced over the years because of a dropping water table and the tremendous increase in ponderosa pine growth over the Black Hills. The thick pine forest reduces the amount of precipitation reaching the ground, and the pine roots take up much of what does.

In addition, many Black Hills streams are now shallower and warmer, largely because of overuse of riparian areas by livestock. The characteristic riparian vegetation once common along Black Hills streams is now mostly gone. This loss contributes to the warming of stream water by allowing more sunlight through to warm the water. Loss of riparian vegetation also allows streams to widen, thus causing them to become shallower. Shallow water warms faster than deep water, contributing to the problem.

Pollution from mining is a serious problem in some streams. Demand for water from Black Hills streams is growing and will continue to grow because of an increase in human inhabitants. All of these factors combine to degrade Black Hills stream habitats. The effect on plants and wildlife, including trout, game animals, and migratory birds has been tremendous.

Black Hills streams of today are much different than when the Custer Expedition came through the area. Lieutenant Colonel Ludlow would scarcely recognize the Black Hills streams he described 122 years ago. And the lake chub may be gone.


UPDATE: In 1996 a population of lake chubs was found in Deerfield Reservoir by SD Game, Fish and Parks fisheries crews. This is the only location that lake chubs can still be found in the Black Hills.

Return to Wildlife Diversity