Imperiled Freshwater Fishes
by
James E. Johnson
National Biological Service
Imperiled Freshwater Fishes | ||
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by James E. Johnson National Biological Service |
| The United States is blessed with perhaps 800 species of native freshwater fishes (Lee et al. 1980; Moyle and Cech 1988; Warren and Burr 1994). These fishes range from old, primitive forms such as paddlefish, bowfin, gar, and sturgeon, to younger, more advanced fishes, such as minnows, darters, and sunfishes. They are not equally distributed across the nation, but tend to concentrate in larger, more diverse environments such as the Mississippi River drainage (375 species; Robison 1986; Warren and Burr 1994). Drainages that have not undergone recent geological change, such as the Tennessee and Cumberland rivers, are also rich in native freshwater fishes (250 species; Starnes and Etnier 1986). Fewer native fishes are found in isolated drainages such as the Colorado River (36 species; Carlson and Muth 1989). More arid states west of the 100th meridian average about 44 native fish species per state, while states east of that boundary average more than three times that amount (138 native species; Figure). | ||
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Figure. Number of fishes considered imperiled and number of native freshwater fishes of the contiguous United States by state (redrawn from Warren and Burr 1994). | |
| Extinction, dispersal, and evolution are naturally occurring processes that influence the kinds and numbers of fishes inhabiting our streams and lakes. More recent human-related impacts to aquatic ecosystems, such as damming of rivers, pumping of aquifers, addition of pollutants, and introductions of non-native species, also affect native fishes, but at a more rapid rate than natural processes. Some fishes are better able to withstand these rapid changes to their environments or are able to find temporary refuge in adjacent habitats; fishes that lack tolerance or are unable to retreat face extinction. | ||
| In 1979 the Endangered Species Committee of the American Fisheries Society (AFS) developed a list of 251 freshwater fishes of North America judged in danger of disappearing (Deacon et al. 1979), 198 of which are found in the United States. A decade later, AFS updated the list (Williams et al. 1989), noting 364 taxa of fishes in some degree of danger, 254 of which are native to the United States. Both AFS lists used the same endangered and threatened categories defined in the Endangered Species Act of 1973, and added a special concern category to include fishes that could become threatened or endangered with relatively minor disturbances to their habitat. These imperiled native fishes are the first to indicate changes in our surface waters; thus their status provides us with a method of judging the health of our streams and lakes. This article compares the two AFS data sets to assess the trends in the status of freshwater fishes in the United States over the past decade. | ||
Basis of the American Fisheries Society Listings |
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| The 1979 and 1989 AFS listings were based entirely on biological considerations throughout the geographic range of the taxon and ignored jurisdictional or political considerations. For example, the johnny darter (Etheostoma nigrum) is a small darter found in clear streams from the East coast to the Continental Divide; the species reaches the western periphery of its range in Colorado. Johnny darters are rare in Colorado, which recognizes the species' rarity (Johnson 1987). Throughout most of its range, however, the johnny darter is common and thus was not included in the AFS listing. Only those taxa that appear imperiled are included in the lists; populations were not considered unless they were distinct enough to be recognized as subspecies. | ||
| The preliminary 1979 AFS listing was obtained by asking knowledgeable fishery scientists which fishes should be included. Those taxa were added to a 1972 listing of protected fishes (Miller 1972) that was then sent out to every state and to selected federal agencies for review. | ||
| The native fish faunas of some areas of the country are better studied than others and may therefore be better represented in the listing. The 1989 listing used knowledgeable biologists but not extensive agency review to build upon the 1979 listing. These two data bases provide the best information presently available on rare native fishes of the United States. | ||
Changes in the Status of Native Freshwater Fishes, 1979-89 |
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| Analysis of the 1989 list provides some basic information on the status and trends of the native fishes of the United States. About one-fourth of our native freshwater fishes are perceived to be imperiled. Ninety-three percent of imperiled species are in trouble because of the deteriorating quality of the aquatic habitats on which they depend; this deterioration results from physical, chemical, and biological effects to our surface waters and underground aquifers. Overuse, introduction of non-native species, disease, and other problems that also affect our native fishes cause much less endangerment than habitat destruction. | ||
| The relation between declining aquatic habitats and fishes facing extinction is not as simple as might be expected. Species with limited distributions are more likely to be jeopardized by changes in their local aquatic habitats than are species with extensive ranges. Many fishes on the lists have local distributions, and a few, such as the Clear Creek gambusia (Gambusia heterochir) and Devils Hole pupfish (Cyprinodon diabolis), are limited to a single spring. These unique fishes could be lost by a single, isolated event. Some of the widespread species included in the listings--such as paddlefish (Polyodon spathula) and six taxa of sturgeons--depend on large rivers, and their inclusion indicates widespread threats to these extensive habitats. | ||
| States with the most listed (imperiled) species include California (42), Tennessee (40), and Nevada (39). Somewhat fewer listed fishes are found in Alabama (30), Oregon (25), Texas (23), Arizona (22), Virginia (21), North Carolina (21), New Mexico (20), and Georgia (20; Figure). Regionally, the Southwest has the highest mean number of fish species listed per state (22.5), closely followed by the Southeast (19.3); the northeastern states have the lowest mean number of native fish species in trouble (3.7). Nearly half (48%) of the southwestern native fishes are jeopardized, followed by fishes of the Northwest (19%), the Southeast (10%), the Midwest (6.4%), the central states (5.9%), and the Northeast (4.3%; Warren and Burr 1994). | ||
| The AFS will likely update its listing of native fishes in peril toward the end of this decade, thus providing us with more than 20 years of information on the status of these fishes, a short time in the overall life of a species but a good data base upon which to evaluate the environmental health of our streams and lakes. If the trend over the last decade continues, we can expect a further decline in the richness of our native fishes. In addition, as aquatic habitat deterioration becomes more extensive, we can expect to see an increase in the listing of widespread fishes. | ||
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National Biological Service Arkansas Cooperative Research Unit Department of Biological Sciences University of Arkansas Fayetteville, AR 72701 |
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| References | |
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Carlson, C.A., and R.T. Muth. 1989. The Colorado River: lifeline of the American Southwest. Pages 220-239 in D. P. Dodge, ed. Proceedings of the International Large Rivers Symposium. Canadian Journal of Fisheries and Aquatic Sciences, Special Publ. 106. Deacon, J.E., G. Kobetich, J.D. Williams, S. Contreras, et al. 1979. Fishes of North America endangered, threatened, or of special concern: 1979. Fisheries 4(2):30-44. Johnson, J.E. 1987. Protected fishes of the United States and Canada. American Fisheries Society, Bethesda, MD. 42 pp. Lee, D.S., C.R. Gilbert, C.H. Hocutt, R.E. Jenkins, D.E. McAllister, and J.R. Stauffer, Jr. 1980. Atlas of North American freshwater fishes. North Carolina State Museum of Natural History. 254 pp. (Reissued 1981 with appendix; 867 pp.) Miller, R.R. 1972. Threatened freshwater fishes of the United States. Transactions of the American Fisheries Society 101(2):239- 252. |
Moyle, P.B., and J.J. Cech, Jr. 1988. Fishes: an introduction to ichthyology. Prentice Hall, Englewood Cliffs, NJ. 559 pp. Robison, H.W. 1986. Zoogeographic implications of the Mississippi River basin. Pages 267-285 in C.H. Hocutt and E.O. Wiley, eds. The zoogeography of North American freshwater fishes. John Wiley and Sons, Inc., New York. Starnes, W.C., and D.A. Etnier. 1986. Drainage evolution and fish biogeography of the Tennessee and Cumberland rivers drainage realm. Pages 325-361 in C.H. Hocutt and E.O. Wiley, eds. The zoogeography of North American freshwater fishes. John Wiley and Sons, New York. Warren, M.L., and B.M. Burr. 1994. Status of freshwater fishes of the United States: overview of an imperiled fauna. Fisheries 19(1):6-18. Williams, J.E., J.E. Johnson, D.A. Hendrickson, S. Contreras-Balderas, J.D. Williams, M. Navarro- Mendoza, D.E. McAllister, and J.E. Deacon. 1989. Fishes of North America endangered, threatened, or of special concern: 1989. Fisheries 14(6):2-20. |