SESSION B:

Title: Identifying historically fishless lakes as a target for conservation

Authors: Katie E. DeGoosh¹ (student), Emily G. Schilling², Cynthia S. Loftin³, Katherine Webster^4
1Department of Wildlife Ecology, University of Maine, 5755 Nutting Hall, Orono, ME 04469-5755; 207-581-1340; katie.degoosh@umit.maine.edu
²Department of Wildlife Ecology, University of Maine, 5755 Nutting Hall, Orono, ME 04469-5755; 207-581-1340; emily.schilling@umit.maine.edu
³USGS Maine Cooperative Fish and Wildlife Research Unit, University of Maine, 5755 Nutting Hall, Orono, ME 04469-5755; 207-581-2843; cyndy_loftin@ umenfa.maine.edu
⁴Department of Biological Sciences, University of Maine, Murray Hall, Orono, ME 04469-5755; 207-581-2542; katherine.webster@umit.maine.edu

Abstract:

Fisheries managers are directed to preserve, protect, and enhance fisheries resources in aquatic ecosystems. Effective management of these systems requires an understanding of their natural history. We suggest that not all lakes in Maine naturally hosted fish populations due to landscape barriers. These fishless lakes provide habitat for a diverse group of organisms that cannot withstand fish predation or competition with fish. The goal of our research is to identify lakes in Maine that historically did not support natural fish populations but now contain fish due to widespread introductions.

We used paleolimnological techniques to identify lakes that were historically fishless using the assemblage of phantom midges (Chaoborus spp.) as a tool to indicate fishlessness. Sediment cores were taken from lakes and fossil mandibles of Chaoborus were enumerated. Top sediment from 21 lakes was used to form a standard calibration set (based on current fish populations) and used to compare with older sediment samples. This calibration set indicates samples with Chaoborus assemblages composed of more than 45% Chaoborus americanus are most likely from fishless ponds. For validation, we analyzed the Chaoborus assemblages in sediment samples that were chronologically dated with Pb210. We were able to identify years when a lake was fishless based on the calibration set, and cross-reference the fishless years with historical stocking records. Our results suggest changes in the invertebrate community of fishless lakes caused by the introduction fish are reflected in the sediment and can reveal information about the history of a lake.