Relationship between river fragment length and persistence of two imperiled great plains cyprinids

We used logistic regression to model the persistence of two imperiled pelagic-spawning cyprinids, sharpnose shiner Notropis oxyrhynchus and smalleye shiner N. buccula, endemic to the Brazos and Wichita Rivers, Texas, USA. There was a significant positive relationship between persistence and river fragment length. Mean length of river fragments in which sharpnose shiner or smalleye shiner still occur was significantly greater (599 ± 27 km) than the mean length of fragments from which these species were absent (187 ± 20 km). Persistence of both species appears to depend on the presence of river fragments long enough to allow spawned ova and swim-up fry time to develop and move out of the current into the backwater areas.