Riverscape fragmentation, hydrologic alteration, and decline of pelagic-spawning fishes in the Great Plains of North America

Declines in abundance and distribution of stream-dwelling fishes are occurring worldwide, including throughout the Great Plains of North America.  Among declining fishes of the Great Plains, eight species that broadcast pelagic eggs during reproduction are declining precipitously. Stream fragmentation and changes in flow regime are two factors associated with declining pelagic-spawning fishes in the southwestern United States; however, it is unclear if the same mechanisms are associated with the decline of fishes unique to the central Great Plains.  We analyzed data from published literature, U.S. Geological Survey streamflow gauges, and direct measurement of stream fragment lengths to summarize characteristics of river systems with stable, declining, and extirpated populations of Great Plains pelagic-spawning fishes.  Preliminary results suggest pelagic-spawning species were extirpated from short stream fragments (<200km) with homogenized flows.  Declining populations persisted in intermediate fragments (200-337km) with homogenized flows, and stable populations were present in longer fragments (>337km) with relatively dynamic flow regimes.  Attenuating fragmentation and managing flow regimes to mimic naturally dynamic flow patterns are potentially useful conservation strategies for pelagic-spawning fishes.