Changes in Fish Communities in Adirondack Lakes

Karen M. Roy1*, Arthur J. Bulger2 and Charles T. Driscoll3

The Adirondack Long Term Monitoring (ALTM) Program collects monthly chemistry in 52 lake watersheds on an ongoing basis since June 1992. During 1994-2005, 45 lakes were surveyed for fish following the same methods of the earlier (1984-87) Adirondack Lakes Survey (ALS) in the region. Fish community changes over the 14-year average interval by class showed: 10 lakes with no fish in either surveys; 8 lakes with no change; 15 lakes gained (mean gain 1.9 species); 8 lakes gained and lost (mean gain 0.9 species), and 4 lakes lost only (mean loss 1.25 species). Fish class comparisons with chemistry means and trends showed the strongest patterns between the fish gain and gain/loss classes with ANC increases and between fish gain with greatest decreases in nitrate. The no fish class was characterized by the highest concentrations of inorganic monomeric aluminum as well as the greatest long-term decreases in inorganic monomeric aluminum.

In the 45 lakes, the 85-87 survey identified 147 fish populations and the 94-05 identified 176, thus adding 29 populations. The median populations increased from 3 to 4 per lake, the maximum number of species increased from 10 to 12, and the average number of species increased from 3.27 to 3.91. Fish community sensitivity metrics developed from the ALS found the greatest gains in the study lakes with starting median pH conditions around 5.5 increasing to about 6.0. Of the 13 sensitive minnows identified in the ALS, three (blacknose dace, fallfish and fathead minnow) were determined to be sensitive and ubiquitous enough to serve as potential indicators. Of these 3 species, one population was observed in 84-87 and four populations in the 94-05 survey. Changes to potential water chemistry critical load indicators (i.e. ANC of 50 ueq/L) were relatively small over the time period with 36 lakes below that level during the 85-87 survey and 33 lakes still below that level in the 94-05 survey. The overall conclusion is that there are signs of recovery in fish species number in some ALTM lakes over the 14 year interval between the two periods. The fish response appears to be modest and mixed, but generally consistent with trends in water chemistry.

This work is conducted by the Adirondack Lakes Survey Corporation and the New York State Department of Environmental Conservation with support from the New York State Energy Research and Development Authority and the USEPA Temporally Integrated Monitoring of Ecosystems/Long-Term Monitoring (TIME/LTM) programs.

1 New York State Department of Environmental Conservation, Ray Brook, NY 12977, 518-897-1354
2 University of Virginia, 3025 Mechum Bank Drive, Charlottesville, VA 22901, 434-977-0349
3 Syracuse University, 151 Link Hall, Syracuse, NY 13244, 315-443-4443