Effect of Climatic Warming on the Southern Margins of the Native Range of Brook Trout, Salvelinus fontinalis

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Abstract
Stream inventories of brook trout (Salvelinus fontinalis) habitat show that the minimum altitude of a brook trout stream in the southern part of the native range rises steadily from sea level at about 39° 12′N, to approximately 640 m at about 34° 40′N at the southern margin of the range. Using this empirical lower stream boundary and a statistical model of the influence of altitude and latitude on groundwater temperature, I suggest that the lower altitudinal margin of the southern part of the native range is shaped by the 15 °C groundwater isotherm. I used the climate warming scenario of the Goddard Institute for Space Studies, GISS, to estimate the increase in groundwater temperature in the native brook trout range, and to estimate the increase in the altitude of the lower stream boundary in a "warmer" climate. The GISS scenario projects a 3.8 °C increase in mean annual air temperature for the southern part of the native brook trout range in the next century, which leads to increases of up to 714 m in the altitude of the lower stream boundary, and to significant reductions in area available for brook trout.