Simulation of thermal/dissolved oxygen habitat for fishes in lakes under different climate scenarios: Part 3. Warm-water fish in the contiguous US

Fish habitat is strongly constrained by water temperature and dissolved oxygen. Thermal/dissolved oxygen habitat for warm-water fish in small lakes was therefore determined from simulated daily water temperature and dissolved oxygen profiles. Twenty-seven types of lakes were simulated with past (1961–1979) climate conditions observed at 209 weather stations in the contiguous USA as input, and with a 2×CO2 climate scenario that is projected to occur at the same locations. The output of the Canadian Climate Centre (CCC) General Circulation Model was used to determine the climate data increments for a doubling of atmospheric CO2. The methodology was described in Part 1 of this paper. The simulation results project the absence of summerkill of warm-water fish in any lake and at any location of the contiguous US under both climate scenarios. Summerkill would occur due to elevated water temperatures or dissolved oxygen deficiency. Under the 2×CO2 climate scenario, the good-growth period is projected to extend from about 75 days at northern latitudes to an entire year (365 days) at southern latitudes. Climate warming to the 2×CO2 climate scenario is projected to have several enhancing effects on warm-water fish habitat in lakes of the contiguous US: (1) Winterkill which occurs in eutrophic and mesotrophic, shallow lakes of the north-central and northeastern US under present climate conditions, is projected to disappear. (2) The good-growth period is projected to be lengthened on average by 30–40 days in lakes at all locations investigated, more in deeper than in shallow lakes and more in northern than in southern latitudes. (3) The highest increase of habitat measured in terms of bottom areas or volumes is projected to be over 200% and to occur at northern latitudes. In several southeastern states good-growth habitat areas and volumes are projected to decrease by up to 30% from the past values, which is the only detrimental impact of climate warming on warm-water fish habitat found in this study.