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ARE CHAOBORUS MANDIBLES IN LAKE SEDIMENTS A RELIABLE INDICATOR OF HISTORICAL FISH ABSENCE IN POST-GLACIATED REGIONS OF MAINE AND MINNESOTA?

Fish introductions can have cascading effects on biological community composition and water quality in historically fishless lakes. The distribution of historically fishless lakes across the landscape in post-glaciated regions is unclear, owing to poor documentation of fish introductions. The aquatic phantom midge, Chaoborus americanus (order: Diptera, family Chaoboridae),is a reliable bioindicator of fish absence in lakes, because it is highly vulnerable to fish predation. Additionally, subfossil remains of C. americanus are persistent in lake sediments, potentially providing a record of historical occurrence of fish in a lake. We isolated Chaoborus mandibles from sediment cores collected from 21 lakes in Maine, and we developed a paleolimnological inference model with logistic regression to predict historical presence of fish. We tested the model with mandibles extracted from 210Pb dated cores collected from 15 Maine lakes with known stocking histories. We compared Chaoborus mandible composition in sediments collected from 15 Minnesota lakes to assess similarities across biogeographic regions, and we found congruence in the two datasets. Our cross-regional model developed from the combined Maine and Minnesota datasets provides a robust tool to assess fish colonization history across a large geographic area.

Holly Kundel (Primary Presenter/Author), Augsburg University, kundelh@augsburg.edu;


Katie DeGoosh (Co-Presenter/Co-Author), Rhode Island Department Of Environmental Management, katie.degoosh@dem.ri.gov;


Cynthia Loftin (Co-Presenter/Co-Author), U.S. Geological Survey, Maine Cooperative Fish and Wildlife Research Unit, cynthia.loftin@maine.edu;


Emily Schilling (Co-Presenter/Co-Author), Augsburg University, schillin@augsburg.edu;