Biodiversity – Fish

Nebraska is in the center of the Great Plains of North America. With its cold winters, hot summers and variable rainfall, it is a harsh place to be a fish. Yet Nebraska is home to more than 100 species of fish, 78 of which are presumed to be native. Nebraska was originally a land of streams and rivers, but immigrants began building dams almost as soon as they arrived, erecting in thousands of ponds, lakes and reservoirs. Fish were stocked in these ponds and lakes, as early as the 1880’s, a practice that continues to this day. So in addition to the native species we now have an additional 25 introduced fishes, as well as six exotic species. More information on fish species found in Nebraska waters is available on the fish identification page.

At risk species

There are seven species of fishes that are at greatest risk of extirpation. These include three big river fishes (pallid sturgeon, lake sturgeon and sturgeon chub) and four small stream fishes (northern redbelly dace, finescale dace, blacknose shiner and Topeka shiner). The big river fishes are found in the Missouri River, where species are at risk due to habitat changes (reservoir construction and channelization). The small stream fishes are at risk because their specialized habitats have been altered or are at risk of disappearing.

Selected species of conservation interest

Pallid and lake sturgeons

The pallid and lake sturgeon, along with their cousin, the shovelnose, prefer large, turbid rivers like the Missouri. Sturgeons are primitive fish and most of their closest relatives have been extinct since the time of the dinosaurs. The skeleton of a sturgeon is mostly cartilage, and the outer parts of the fish are armored with rows of bony plates. The sturgeons have a distinctive flattened head, on the bottom of which is found the sucker-like mouth and four barbels hanging down. The intestine of a sturgeon is similar in structure to that of sharks in that it has a spiral valve, which forces the food to follow a spiral path during digestion.

Glacial relict fishes

During the Pleistocene, a succession of ice sheets advanced south from the Arctic, several of which reached as far south as Kansas. The cooler climate that brought the ice sheets allowed many species of northern animals to extend their ranges south into the Plains. When the climate warmed and the ice sheets melted, several fishes stayed behind, living in streams that were fed by cool groundwater. We call these fishes “glacial relicts”. Among them are the Northern redbelly dace, the finescale dace and the northern pearl dace. These fishes prefer cool, clear, vegetated habitats, and their presence indicates a high-quality stream.

Plains topminnow

Aside from a second, smaller population center in southern Missouri, this is the one species of fish that is virtually unique to Nebraska. While a small number of individuals have been found in Colorado, Wyoming, South Dakota, Minnesota and Iowa, in Nebraska, the plains topminnow can be found in most of the major river systems north of the Platte River, and are most abundant in the Sandhills. Topminnows are most commonly found within beds of vegetation in clear headwater streams. This species feeds on a wide variety of small invertebrates, including crustaceans, aquatic and terrestrial insects, and snails. Its life span is up to 4 years and its maximum size is about 2½ inches.

Major issues and threats

The threats to fishes are those that threaten streams in which they live and the variety of habitats within the streams. These include: groundwater pumping, sedimentation, pesticides, herbicides and other chemicals, degradation by livestock, drought and dewatering. Physical alterations of streams can affect fishes as well. These alterations include include channel alterations (straightening and dredging) and fragmentation of streams by dams and culverts.