Meeting Abstract
Dams are one of the most widespread and disruptive anthropogenic modifications of ecosystems worldwide. While it has been shown that large dams with upstream reservoirs can cause divergent selection in fish morphology, the effect of small dams without an upstream reservoir is largely unknown. We investigated the contribution of isolation to morphological variation in fishes while controlling for divergent flow selection created by an upstream reservoir. This project also investigated the effects of isolation time on fish morphology by comparing morphological divergences of fish associated with older barriers (waterfalls) to very new barriers (dams). A total of 950 fish across 18 species were sampled from May to August in 2014 from nine waterfalls and five dams in the southern Lake Superior Watershed. Geometric morphometrics will be used to analyze body shape differences between fish above and below barriers. Initial results show significant differences in mean total body length between above and below populations at three study sites: Rhinichthys cataractae separated by Middle river dam (WI), Cottus cognatus separated by Miners falls (MI), and Cottus cognatus separated by Au train falls. These findings suggest that genetic drift due to isolation from small dams and waterfalls can lead to morphological variation in native fish populations.
