Date of Award

8-2007

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Ecology and Environmental Sciences

Advisor

Cynthia S. Loftin

Second Committee Member

Katherine E. Webster

Third Committee Member

Dennis Anderson

Abstract

Knowledge of historical conditions provides baseline information to ecologists and resource managers for assessing environmental change, predicting system responses, and developing management goals. During the last century, fish introductions for recreational purposes were widespread, obscuring natural fish distributions in Maine lakes. The goal of this study was to use paleolimnological techniques to identify lakes that currently contain fish but may have been historically, naturally fishless lakes. I developed a paleolimnological inference (PI) model using the assemblage of phantom midges (Chaoborus) in surface sediments from a standard calibration set of 21 Maine lakes. Patterns of mandible density and Chaoborus mandible distribution in fishless and fish-containing lakes indicate that relative abundance of C. americanus, rather than its presence alone, was the best indicator of a fishless lake in Maine. The PI model, developed using logistic regression, accurately classified fishless lakes 84% of the time. To further evaluate use of the model, we analyzed the Chaoborus assemblages in sediment samples from cores that were chronologically dated with 210Pb collected at three historically fishless lakes with documented fish introductions. We were able to verify the lakes were historically fishless with the PI model. Then, the PI model was applied to sediment cores from 15 lakes in the region to identify lakes that currently contain fish but may have been fishless historically. The PI model suggested that 10 of the study lakes had > 57% probability that they historically were devoid of fish populations. This research establishes an approach for identifying historical fish absence in lakes using paleolimnology and is an integral step in planning adaptive management strategies for Maine’s historically fishless lakes

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