Minimal effects to genetic diversity and population structure in seven fish species isolated by a hydroelectric dam

Abstract

Reduced connectivity created by artificial barriers can influence the genetic integrity of isolated subpopulations by reducing local population sizes and altering patterns of historic gene flow. I investigated the genetic impacts of one such barrier, the Prairie du Sac dam, Wisconsin, USA, using microsatellite data from seven fish species with varying life history traits sampled above and below the dam. Contrary to many past studies in other systems, I did not detect any significant differences in genetic diversity between populations found above and below the Prairie du Sac dam. Results revealed low genetic differentiation (FST = 0 – 0.008) between populations above and below the dam for all species. In fact, more genetic variation was partitioned among sampling years than between above and below dam populations for all but one of the species. Results from simulations designed to model my study system indicated that the genetic impacts of the dam will likely be detectable approximately 40-60 generations after the dam was constructed. These simulations also suggested it may be possible to lessen the genetic effects of the dam with a fish passage strategy that facilitates a migration rate of > 1% between above and below dam populations. In summary, my findings indicate the genetic effects of dams can be variable, and that fish passage strategies could dampen genetic differentiation if designed appropriately.