by Robert A. Hrabik
Fisheries Management Specialist
Missouri Department of Conservation
formerly Curatorial Assistant, Zoology
University of Nebraska State Museum
and Conservation Technician
Nebraska Game and Parks Commission.

Introduction

A fascinating array of aquatic organisms thrives in the Sand Hills region. Few are as intriguing, however, as the fishes. Lake habitats provide much of the sport fishing today, yet the stream fisheries of the Sand Hills also offer Nebraskans a tremendous opportunity to satisfy many unmet demands anglers may have. The large diversity and uniqueness of some Sand Hills fishes offer nature enthusiasts and scientists a rich area for study. Because the distribution and associations of Sand Hills fishes have remained relatively unaltered by human activity, they can be used to monitor environmental change in the region. Fish have long been used as indicators of the quality of the environment (Karr, 1981) (see Maret on using fish to assess water quality after this chapter).

More than 75 species, representing 10 orders and 15 families, have been found in Sand Hills streams and lakes at some time (table 9-1). Widespread and/or rather common Nebraska species such as the gar, gizzard shad, and goldeye, considered primitive fishes, are uncommon in the Sand Hills, while others such as the sunfish, perch, and drum, which are derived or more recent fishes, are fairly common. Rare Sand Hills species, some of the rarest fishes in Nebraska incidentally, include some of the daces and shiners (minnows, Cyprinidae). Many are associated with northern climates and are intolerant of variation in habitat. However others, such as the blacknose dace, common shiner, and bluntnose minnow, fishes with eastern affinities, are more tolerant of environmental changes.

On the other hand, some fish, particularly the big river types, are widespread, often generalist, species able to withstand wide environmental extremes. This group includes the flathead chub, speckled chub, silver chub, stonecat, channel catfish, quillback, and river carpsucker. Other species that commonly occur in the Sand Hills are pioneering types that are able to withstand extreme, sometimes polluted environmental conditions. Three of the most tolerant pioneering species are the red shiner, fathead minnow, and common carp. Other pioneering types include the sand shiner, bigmouth shiner, and green sunfish. The white sucker is common in small to medium sized streams. Though widespread in Nebraska, it only occurs in moderately unpolluted environments and thrives in organic pools of low-gradient streams.

Several species, such as the Iowa darter and the brassy minnow, for example, have populations scattered throughout Nebraska but are most commonly found in the Sand Hills. The brassy minnow is peripheral in Kansas (Cross and Collins, 1975) and rare in Missouri (Pflieger, 1975), while the Iowa darter occurs no farther south than Nebraska (Lee and others, 1980). Similarly, the brook stickleback used to be considered a threatened species (in need of protection and preservation) in Nebraska, but because of the stabilization of the Sand Hills population and an apparent increase statewide, it was removed from the Nebraska threatened species list (Ross Lock, personal communication).

If Nebraska were to be represented by a state fish that is also endemic (native) to the plains, it would have to be by the plains topminnow. This fish is common statewide in suitable habitats, but is particularly common in the Sand Hills. It appears that two disjunct population centers of this species occur, one in southcentral Missouri (Pflieger, 1975) and the other in Nebraska. Although it is also found in South Dakota, Wyoming, Colorado, Iowa, Kansas, Missouri, and Oklahoma (Lee and others, 1980), nearly 90 percent of the northern population\'s range is within Nebraska; however, in Iowa this species may have been extirpated (eliminated) (Harlan and Speaker, 1987). Overall, the Nebraska distribution accounts for more than 60 percent of its range.

So fascinating are these little marvels that they are sold as aquarium species abroad. Although called a minnow, the topminnow is not really a minnow but belongs to the family Fundulidae. It formerly belonged to the Cyprinodontidae (Parenti, 1981; Able, 1984), which also includes the famous desert pupfishes of the southwestern United States.

The Stability of Sand Hills Aquatic Ecosystems

A key factor affecting the presence and distribution of fish species in the Sand Hills is the stability of the habitat in the region. Sand Hills streams exhibit a remarkable uniformity in flow (see streams chapter). Percolation of water is so greatly enhanced by the high sand content of the Valentine soil that rainwater, even during intense storms, is absorbed and transmitted through the soil to the groundwater. In turn, the groundwater provides the rivers and streams with a source of water that is relatively constant in quantity and temperature. For this reason the range between minimum and maximum daily discharge on most Sand Hills rivers and streams is very small. The Dismal River, for example, has been called one of the most uniformly flowing streams in the world (Keech and Bentall, 1971). This is unlike most prairie and agricultural watersheds, where streamflows may vary by several thousand cubic feet per second.

Stability in flow lessens the chance of catastrophic events, such as floods, and decreases the likelihood of periodic episodes of silt deposition, erosion, or dewatering of the stream. Stability also may be associated with greater productivity (John Orsborn, personal communication). Also, certain Sand Hills species, particularly those occupying headwaters, are so adapted to this stability that their survival would be severely affected if the streams underwent large fluctuations in flow.

In addition, because of the high sand content of the soils and the presence of a grass cover, the runoff of water to streams is virtually clear, particularly in comparison with runoff from row-crop areas. The relative lack of clay or mud sedimentation in the streams augments aquatic stability. Uniform flows and clear water also enhance fish habitats by promoting vegetative growth, which provides a refuge for young fish and supports a myriad of invertebrates, an important food source for fish. Riparian vegetation also stabilizes stream banks, decreases erosion, and, by constricting flows, deepens the channel and enhances the pool-to-riffle ratio. Without this riparian vegetation, sand bedload would probably increase and change the nature of the habitat.

Many permanent marshes and lakes also provide a stable, groundwater-fed environment for fish. Some marshes have constantly flowing water because they are actually the headwaters of streams. It is in these stable marshy headwater areas where some of Nebraska\'s rarest species thrive. Other marshes, however, are too alkaline, shallow, or unstable to support fish.

Sand Hills Species and Affinities

Native Species

In the Sand Hills, one can find fishes with affinities to fish faunal regions representative of the east, west, north, and south (fig. 9-1)[1]. For example, the longnose dace is representative of the Western High Plains faunal region (fig. 9-1). This species is predominantly linked to the Niobrara River system as it crosses the Sand Hills on its way to the Missouri River. However, longnose dace also occur in the headwaters of the Loup River system and the North Platte River. The Eastern faunal region is represented in the Sand Hills by the blacknose dace, bluntnose minnow, common shiner, johnny darter, and central stoneroller. The southern region is represented by the plains killifish, suckermouth minnow, western silvery minnow and plains minnow. The southernmost part of the native range of some northern species extends into the Sand Hills, but no further. These northern species include the northern redbelly dace, finescale dace, pearl dace, blacknose shiner (except for a disjunct population in Missouri; Pflieger, 1975), and the lake chub. All the northern species appear to be intolerant of habitat and environmental deviations and thus are restricted to headwater springs, where the environment is particularly stable. Most of these northern species occur in the Niobrara River and Snake River drainages, but several occur in the Loup River system and North Platte River drainages as well.

Many other Sand Hills species are associated with two or more faunal regions or are generalist or pioneering species. For example, the brook stickleback is primarily a northern species, but also occurs in the Western High Plains and Eastern Prairie regions. It does not occur any farther south than Nebraska (Lee and others, 1980).

Of special interest are several Sand Hills species the populations of which are isolated far from the species\' geographical centers. The blacknose dace is of miles from its eastern population center but endures in the Sand Hills (Lee and others, 1980). Another species, the pearl dace, has a range that stretches as far north as the Northwest Territories in Canada, east to Nova Scotia, and south to Wisconsin. Although virtually no pearl dace populations occur in the states surrounding Nebraska, a substantial population of pearl dace exists in the Sand Hills.

Origin of Sand Hills Fishes

The presence in the Sand Hills of so many different kinds of fish with affinities to so many different faunal regions poses an interesting problem. Why are there so many different faunal regions represented in the Sand Hills and how did they get there? Those northern and eastern species that are isolated far from the rest of their populations pose a particularly interesting problem.

The current species distribution can perhaps be explained by looking at the course of the rivers that flowed through the area before and during the period of glaciation. It is possible that during the advance of the glaciers, when the central plains had a much cooler climate, fish from rivers to the north and east moved into streams within and around the Sand Hills. After the glaciers retreated, a warmer climate prevailed on the plains, but conditions in the groundwater-fed streams in and around the Sand Hills may have remained stable enough to support these northern and eastern species as glacial relicts (persisting remnants). This explanation could account for the existence of the isolated populations of the blacknose dace of eastern affinity and the pearl dace, with affinities to northern faunal regions.

Stream piracy or capture, the changing of course of a river or stream so that it cuts through and captures the water of another, is also a possible explanation for the origin of isolated populations, in particular, for the presence of southern species in the Sand Hills. At one time many rivers in western Nebraska, Kansas, and Oklahoma flowed southward. The southern plains species may have traveled up these rivers to enter Nebraska. When these southern-flowing rivers were captured by eastern-flowing drainages, these fish were left in suitable Sand Hills habitats. Likewise, many large river species may have moved into the Sand Hills from the Mississippi River drainage.

Introduced Species

On the other hand, the origin of some Sand Hills species is easy to explain. Thirteen species have been introduced into the Sand Hills ecosystem. Most of these introductions were carried out to satisfy the growing demand for a Sand Hills sport fishery. Some, such as the Coho salmon, did not survive; others, such as the alewife, remain isolated; but many others, such as carp, bluegill, and trout, have done well. Three species of trout-the brook, brown, and rainbow have been introduced into the Sand Hills and are available to anglers. However, there are few naturally recruiting populations and most are maintained by supplemental stocking. In some streams they provide good fishing; in others actual harvest is not known.

To create a sport fishery in some alkaline Sand Hills lakes, D. B. McCarraher introduced white perch (Hergenrader and Bliss, 1971). The experimental introduction was a failure because the species became so prolific they dominated the lake environments with detrimental effects on many of the native species. The white perch were artificially eliminated from the Sand Hills in the early 1970s (Gene Zuerlein, personal communication) and to all available knowledge have not resurfaced. This experience demonstrates why introductions of exotic species should be carefully examined, so that elimination of desirable native species is avoided.

Distribution within the Sand Hills

The distribution of most Sand Hills fish species is linked to rivers and their drainages. Many more species, more than 94 percent, are associated with streams and rivers than with lakes. The largest number of species occur in the Niobrara River drainage (Bliss and Schainost, 1973a). This drainage, together with that of the Platte, enables this sub-basin to have the second highest number of species in the entire Missouri River basin (Cross and others, 1986). The glacial relicts and species with eastern affinities account for this richness.

Although two species, the muskellunge and alewife, are landlocked, occurring only in Merritt Reservoir in Cherry County, most Sand Hills fish have a wide distribution, encompassing more than one river system. The distribution of species within a given river system, however, is not widespread. As a rule, river habitats and the association of fish species in them change dramatically as the stream widens along its course from the headwaters to the mouth. At the headwaters, rivers may be fairly stable and support species intolerant of habitat degradation or pollution. As the stream widens, the chances of environmental and habitat variation increase. A larger stream has a wider flood plain; hence, the influence of agricultural and natural events also markedly increases. Not surprisingly, a corresponding shift in species can be readily observed from intolerant headwater species to the more tolerant river types. Thus, one of the best ways to describe the distribution of fish in the Sand Hills is to describe where in the rivers they can be found.

People studying rivers often classify the different segments of a river into different groups or stream orders. Numbers are assigned to these classifications to indicate the approximate size and general characteristics of the river reach. Low numbers refer to reaches near the headwaters of the stream; high numbers refer to reaches near the mouth (Strahler, 1957). As a general rule, the diversity of fishes increases with stream order.

Typical Sand Hills headwater species, stream orders 1-3, are the minnows, trouts, killifishes, sticklebacks, and darters. More specifically, these associations may include the central stoneroller, brassy minnow, bigniouth shiner, sand shiner, creek chub, plains topminnow, white sucker, and Iowa darter. Other species that frequent or are typically headwater inhabitants but are less common include grass pickerel, common shiner, fathead minnow, longnose dace, black nose dace, pearl dace, finescale dace, northern redbelly dace, black bullhead, brook stickleback, and rainbow trout.

Some of these species may become dominant in headwater situations, displacing the more common species. Northern redbelly dace and finescale dace are excellent examples. The fact that these two species often coinhabit and hybridize in headwater streams further enforces their dominance (Stasiak 1977, 1978; Joswiak and others, 1982). Identification of these hybrids is sometimes laborious, particularly to the untrained eye.

Medium-sized rivers, stream orders 4-6, generally show an increase in predators and specialists, leading to an increase in species diversity. Typical species found in these habitats include common carp, plains minnow, western silvery minnow, flathead chub, red shiner, suckermouth minnow, and stonecat. In addition, several species from both the headwaters and large river systems may be found in streams of these orders.

Very large rivers, stream orders 7-12, do not exist in the Sand Hills. However, typical large river species, such as the gar, shad, goldeye, sucker, catfish, and perch, can be found in the Loup and Niobrara rivers. The more common large river species include the speckled chub, silver chub, emerald shiner, river shiner, carpsucker, buffalo, channel catfish, flathead catfish, sauger, walleye, and freshwater drum. Several of these species can endure wide variations in their environment.

Though the environment of Sand Hills streams can sometimes be capricious, it is generally very stable in comparison to lake habitats (McCarraher, 1977; Steen, 1961). Many Sand Hills lakes are slightly to strongly alkaline. There are also many marsh-type lakes in this region. Those that have permanent pools host abundant submergent plant life and aquatic invertebrates, including phyllopods; hardstem and three-square bulrush are common near the pool perimeter.

A great majority of the Sand Hills lakes cannot support a fishery. Many more are borderline due to their shallowness or chemical properties. Throughout the summer these intermittent lakes are warm and stable and dissolved oxygen remains abundant. However, the dissolved oxygen rapidly deteriorates during the winter months, and little dissolved oxygen is available by late winter.

Those lakes that are borderline do support fish, although only a limited number of species can survive high alkalinities. The desirable range of alkalinity for good fish growth varies between 20-300 mg/l (Boyd and Lichtkoppler, 1979). Levels higher than that often cause carbon dioxide to be in short supply, thereby limiting phytoplankton and photosynthesis. Dangerously fluctuating pH levels can occur under these situations. Apparently, high alkalinities, such as those that occur in some Sand Hills lakes, chemically influence the survival of fish eggs and fry.

The species most tolerant of high alkalinities is the fathead minnow. In many of the highly alkaline lakes of Garden County, fathead minnows are the only species found; however, other alkaline tolerant species may be found. Generally, the perch and pikes can tolerate higher alkalinities than the sunfishes. Yellow perch, grass pickerel, northern pike, and black bullhead can withstand elevated alkalinities and are first to succeed in recolonizing lakes that previously could not support fish. Yellow perch, however, seldom occurs in a lake by itself and is commonly found in a mixed population of largemouth bass, green sunfish, bluegill, black crappie, and northern pike. Of the Esocids, the grass pickerel is better adapted to the shallow, alkaline lakes in the western Sand Hills because its physiology enables it to withstand higher water temperatures, lower levels of dissolved oxygen, and water-level fluctuations.

In the early 1960s, McCarraher introduced the Sacramento perch from Nevada, with limited success. The only native sunfish of the western United States, this species is well adapted to alkaline environments. It was believed a sport fishery in Sand Hills lakes could be created where alkalinity limited the survival of other species. Sacramento perch were stocked in a variety of Sand Hills lakes through the early 1960s. They fared well in some lakes, poorly in others. In one pond, Sacramento perch survived alkalinity measurements over 5,300 mg/l, the highest alkalinity value recorded for the survival of this species. However, it was found that temperature and the physiological effects of high Sand Hills alkalinities limited successful reproduction of the species. The program was abandoned in 1962, and the distribution of the species dwindled to a few suitable locations. By 1986, the U.S. Fish and Wildlife Service at Valentine announced that Sacramento perch no longer existed in the refuge lakes and that the species was probably on the verge of extirpation throughout the Sand Hills.

The more freshwater lakes of the region support excellent fisheries of special interest to anglers. Common species include largemouth bass, bluegill, yellow perch, black crappie, walleye, channel catfish, and northern pike. One of the largest and most southern, naturally occurring populations of northern pike inhabits the Sand Hills. Although most prevalent in lakes, they also inhabit some of the streams. These are ordinarily less than 24 inches and 3 pounds, but lunkers more than 10 pounds and 32 inches are rather common.

Currently, lakes provide the majority of fishing in the Sand Hills and in geologic time past, many, particularly in Cherry County, were once large lakes. Though they are gradually aging through natural processes, no evidence suggests that the lakes are undergoing accelerated eutrophication that would cause ecological concern.

Although from the description above, it may appear the Sand Hills fishes are well known, this is not the case. Unfortunately, many streams and rivers within the Sand Hills are virtually inaccessible and have never been sampled. On others, distributional investigations have been attempted (Bennett, 1931; Johnson, 1942; Bliss and Schainost, 1973a, 1973b), but because only a few accessible areas were sampled, total distributions are inadequately described

The lack of proper studies is a major problem, particularly for determining the distributional limits of Nebraska\'s rare or uncommon fishes, many of which occur in the Sand Hills. An attempt was made by Madsen (1985) to summarize all known distributional data for Nebraska\'s rare fishes. She also did some sampling of a few Sand Hills streams. However, more recent surveys have still yielded new records, an indication that Sand Hills fish distribution needs further study.

This could not be better exemplified than by the rediscovery of the lake chub (Stasiak, 1986). Last collected in Nebraska in 1892 by Evermann and Cox (1986) and determined to have been extirpated by Madsen (1985), the species was sampled in the headwaters of Bone Creek near Ainsworth in 1985. Madsen (1985) also reported sampling one of Nebraska\'s rarest species, the blacknose shiner, nearly 165 miles west of its only known thriving population.

Another uncommon species, the bluntnose minnow, inhabits the upper Elkhorn River and its tributaries. The Elkhorn borders the Sand Hills region, and some tributaries originate in Sand Hills soils. Bliss and Schainost (1973a) reported the sampling of the bluntnose minnow from east Holt Creek, a creek just outside of the Sand Hills in Keya Paha County (Niobrara drainage). No voucher specimens (specimens providing proof) exist, however, and the claim has not been substantiated since. This is also the case for the tadpole madtom, a small member of the catfish family. A rather common inhabitant of the upper Elkhorn River, it has not been taken recently in the Loup nor Niobrara systems. It has been identified, however, from the fossil record (Comer, 1982) in the Loup drainage near Litchfield, Nebraska (just 40 miles southeast of the present Sand Hills). Thus, it could have inhabited the Sand Hills during the Pleistocene age (1.6 million to about 10,000 years ago). There are suitable Sand Hills habitats for the species, however, and the sampling of specimens, though unlikely, is possible.

A more recently confirmed species, the johnny darter, was long thought to have occurred in the Niobrara River system. It has been consistently sampled in the Missouri River near the Niobrara confluence (Hesse and Mestl, 1984, 1985). A single specimen of johnny darter was confirmed from Merritt Reservoir (R. H. Stasiak, personal communication) in 1985. A second specimen was identified later that year. Thus, the Snake and lower Niobrara rivers can be included as possible extensions of the native range of this species.

The orangethroat darter occurs in tributaries to the Platte and North Platte rivers that originate in Sand Hills soils in Keith, Lincoln, Garden, and Morrill counties. Though locally abundant, they are peripheral to the region and therefore are an uncommon addition to the fauna of the Sand Hills.

These discoveries indicate that little is known of Sand Hills fish distribution and, in particular, that of uncommon species. Indeed, other species thought to have been extirpated in Nebraska may be thriving in some isolated marsh or headwater stream that has never been sampled simply because it is difficult to reach.

Species Loss

Fortunately, compared to other faunal regions, the Sand Hills have been spared significant loss in species diversity. To the knowledge of specialists, only one species confirmed to have been an inhabitant of the Sand Hills has been lost, the highfin carpsucker. Though the species prefers medium to large rivers, it does not tolerate silt and turbidity and is most often found over firm sand or gravel bottoms. This species is disappearing over a great deal of its native range, presumably due to siltation. Very little is known of its habits and life history. In Nebraska, the species was last collected in the early 1940s (Johnson, 1942).

Two other species occurred very near the periphery of the Sand Hills and may have had populations in Sand Hills streams. The Topeka shiner was one of the most commonly collected species in north-central Nebraska at the turn of the century (Evermann and Cox, 1896) and was indeed found elsewhere in the state (Madsen, 1985). The advent of mechanized agriculture and intensive farming increased sedimentation to the point where it eliminated this species. None have been collected in the state since 1940 (Johnson, 1942). Topeka shiners were inhabitants of the upper Elkhorn and lower Niobrara systems. Blackside darters were also found in the upper Elkhom system (Madsen, 1985) and were last collected at the turn of the century to the stream ecosystem in the Sand Hills by Evermann and Cox (1896). Populations of this species and Topeka shiners may have occurred in Sand Hills streams in Rock, Holt, and Antelope counties. But because early distributional assays of Nebraska fishes were so sparse, range limits of these species are difficult to define.

The list of extirpated species was recently reduced with the rediscovery of the lake chub. This species was previously collected in Minnechaduza and Schlagel creeks in Cherry County and Long Pine Creek in Brown County in July 1893 (Evermann and Cox, 1896).

Several other Sand Hills species, the northern redbelly dace, pearl dace, finescale dace, and blacknose shiner are currently listed as threatened species by the Nebraska Game and Parks Commission. Although not officially designated as threatened species, the lake chub and several other species are also in need of protection and conservation (Madsen, 1985).

Of some concern and a general threat to the stream ecosystem in the Sand Hills is the possible occurrence of acid rain. Because the water in the Sand Hills streams does not flow through limestone formations, which can neutralize the effects of acid rain, Sand Hill streams may be particularly susceptible to this threat.

Footnotes

[1]Faunal regions herein described have not necessarily been accepted by Nebraska authorities, but were chosen and named by the author to identify faunal fish associations.

References

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