Assessment of Changes in Cold Water Lake Habitat in the
Upper Mersey Watershed
SUMMARY
A survey of five lakes located within the upper Mersey watershed was carried out to assess the degree to which they presently contain summer cold water habitat, and to determine if current levels of cold water lake habitat differ from that observed during surveys carried out several decades earlier. Of the five lakes surveyed, four lacked suitable cold water habitat during August, and the remaining lake only contained suitable cold water habitat within the lower portion of the metalimnion. When compared to surveys carried out two to three decades earlier, all of the lakes except one exhibited a significant decrease in cold water habitat. This decrease was due to reduced levels of dissolved oxygen rather than elevated water temperatures.