Wetlands and Aquatic Research Center - Florida
U.S. Geological Survey
Extinct North American Freshwater Fishes
Noel M. Burkhead, U.S. Geological Survey, Southeast Ecological Science Center, Gainesville, Florida
Extinction is a natural process in nature and is the opposite of speciation—the evolution of new life forms. Importantly, 90%–96% of all species that became extinct over geological time disappeared during the normal give and take of speciation and extinction1. There is widespread evidence that modern rates of extinction in many plants and animals significantly exceed background rates in the fossil record. From 1900 to 2010, 57 species and subspecies of North American freshwater fishes became extinct, and since 1898, three distinct populations of valued fishes were extirpated from the continent2. Intuitively, this number of extinctions seems unnaturally high. Since the first tally of extinct North American fishes in 19893, the number of extinct fishes increased by 25%2,4. From the end of the 19th century to the present, modern extinctions varied by decade but significantly increased after 1950. The post-1950s increase in extinction rates likely corresponds to substantial economic, demographic, and land-use changes that occurred in North America after WWII2.
A meaningful way to evaluate modern extinctions is to compare modern rates of extinction to background rates using data from the fossil record2,5. The mean background extinction rate (from origination to extinction) for freshwater fish species is estimated to be one extinction/3 million years5. The modern extinction rate in North American freshwater fishes is conservatively estimated to be 877 times greater than the background rate—for the interval 1900 to 20102. Calculation of modern to background extinction rate (M:BER) is similar to extinctions per million species years (E/MSY)7 but differs in that actual background extinction rates are used in lieu of one extinction/million years.) M:BER ratios fluctuate by year because total North American fishes increases each year due to descriptions of new species and because extinctions are intermittent (the last one occurred in 2006). The M:BER value for North American freshwater fishes in 2012=863 and will continue to decline annually until the next extinction occurs. During the 20th century, freshwater fishes had the highest extinction rate among all vertebrates worldwide2. Low numbers of fish extinctions documented from other continents suggests that extinctions are under-reported in Africa, Eurasia, and South America at this time2,6. It is estimated that future extinctions in North America will increase from 39 currently extinct fish species to between 53 and 86 species by 2050.
The information on extinct fishes presented here is an offshoot of the American Fisheries Society’s conservation assessment of North American fishes4. This preface and supporting information are intended to provide basic background information on extinction, with specific information on North American fishes for students and professional biologists. Supporting information includes definitions of extinction and endemism, references on extinction rates and biodiversity (emphasizing fishes), and resource links to the web. Three maps and complementary tables are ecoregions of North America, extinct fishes by ecoregion, extinct fishes by provinces and states, and a downloadable data summary in Excel.
(Data compiled in 2012)
1. May RM, Lawton JH, Stork NE. 1995. Assessing extinction rates. Pages 1–24 in Lawton JE, May RM, eds. Extinction Rates. Oxford University Press.
2. Burkhead NM. 2012. Extinction rates of North American freshwater fishes, 1900 to 2010. BioScience 62 (9): 798-808. [PDF Document version, 6.2mb].
3. Miller RR, Williams JD, Williams JE. 1989. Extinctions of North American fishes during the past century. Fisheries 14: 22-30, 32-38.
4. Jelks HL, Walsh SJ, Burkhead NM, Contreras-Balderas S, Díaz-Pardo E, Hendrickson DA Lyons J, Mandrak NE, McCormick F, Nelson JS, Platania SP, Porter BA, Renaud CB, Schmitter-Soto JJ, Taylor EB, Warren ML, Jr. 2008. Conservation status of imperiled North American freshwater and diadromous Fishes. Fisheries 33 (5):372-407.
5. Stanley SM. 1985. Rates of evolution. Paleobiology 11: 13-26.
6. Snoeks J, Harrison IJ, Stiassny MLJ. 2011. Chapter 3. The status and distribution of freshwater fishes. Pages 56-73 in Darwall WRT, Smith KG, Allen DJ, Holland RA, Harrison IJ, Brooks EGE, eds. The Diversity of Life in African Freshwaters: Under Water, Under Threat. An analysis of the status and distribution of freshwater species throughout mainland Africa. International Union for the Conservation of Nature.
7. Pimm S, Raven P, Peterson A, Sekercioglu CH, Ehrlich PR. 2006. Human impacts on the rates of recent, present, and future bird extinctions. Proceedings of the National Academy Sciences 103: 10941–10946.