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Zebra Mussels (Dreissena polymorpha) are an invasive mussel species that are native to Eurasia, and were introduced into the United States in the 1980s. Since their arrival, Zebra Mussels have spread across most of the U.S. and were first found in South Dakota in 2015 in the lower part of the Missouri River and Lewis and Clark Lake. In 2019, Zebra Mussels were detected in Lake Sharpe for the first time. As these mussels begin travelling north through the Missouri River, it became apparent that a method was needed to control their numbers. One potential biocontrol agent for Zebra Mussels is the native South Dakota state threatened False Map Turtle (Graptemys pseudogeographica) which are known to consume mussels in other parts of their range. We wanted to know if these turtles would consume Zebra Mussels in a laboratory setting, and if turtles from a previously colonized area (59 Mile Stretch) would consume more than turtles from a non-colonized area (Lake Francis-Case). False Map Turtles were collected from the 59 Mile Stretch (n=25) and Lake Francis-Case (n=23), and Zebra Mussels were collected from Lewis and Clark Lake. Turtles were placed in individual aquaria and presented with five snails and five mussels of three size classes for 24 hours. On average, more small mussels were consumed than medium or large (p<0.05). There was no significant difference in mussel consumption by experienced and naïve turtles. These results demonstrate that False Map Turtles can serve as a biocontrol agent for Zebra Mussels in the Missouri River in South Dakota. Turtles’ readiness to consume mussels regardless of if they had previously been in contact with the mussels and their propensity to consume small mussels could help quell initial invasions through overall consumption and by consuming immature mussels before they have a chance to breed.

First Advisor

Jacob Kerby

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