Springs in time: fish fauna and habitat changes in springs over a 20-year interval

1. Despite the range of threats to springs and the number of spring-endemic species, studies of temporal changes in the fauna of springs have rarely been reported. Changes in the fish of 22 Oklahoma (USA) springs were compared among surveys in 1981, 1982, and 2001. 2. Twenty-year assemblage differences were correlated with physical alteration of specific springs and stocking of native fish, which was made possible by past habitat changes that produced pools. Physical alteration of springs is a major ongoing threat to Oklahoma springs. 3. Variation in spring fish assemblages among the three surveys was apparently affected by fish movement in and out of springs, and the greater rain-induced connectivity between springs and streams during one year. 4. Although flow reduction is a commonly cited threat to springs, there was little evidence of flow reduction impacts in this study because Oklahoma springs may have been affected prior to 1981 and high-flow springs, which most often contain fish, were in areas with low groundwater water use. Copyright # 2008 John Wiley & Sons, Ltd. Received 13 December 2006; Revised 17 May 2007; Accepted 24 June 2007