Hydroelectric dams look like barriers between bodies of water, where fish on one side of the dam live and breed without interacting with fish on the other side. We wanted to know how a Winnipeg River dam, the Slave Falls Generating Station (GS), had actually impacted a long-lived fish, the Lake Sturgeon (Acipenser fulvescens). Do the sturgeon upstream and downstream of the dam live and interact differently since the dam was built? We caught fish and analyzed their size and genetics on both sides of the dam and compared our results to a computer simulation that modeled fish population genetics. We found that the Slave Falls GS is not that different than the waterfall that existed nearby in the recent past, in terms of preventing Lake Sturgeon from swimming upstream and mating with the fish that live in that area.