To project fish habitat changes of 57 fish species under potential global warming,
their suitable thermal habitat at 764 stream gaging stations in the contiguous US was
studied. Water temperature records were available at these gaging stations. Global
warming was specified by air temperature increases projected by the Canadian Center of
Climate Modelling general circulation model for a. doubling of atmospheric C02. The
thermal regime at each gaging station' was related to air temperature using a nonlinear
stream temperature/air temperature relationship.'
Suitable fish thermal habitat was assumed to be constrained by both maximum
temperature and minimum temperature tolerances. Streams with weekly water
temperatures between the maximum and minimum temperature tolerances of a fish
species were considered to provide suitable thermal habitat for that fish species: Because
information on minimum temperature tolerance of many fish species could not be found,
both a 0 °C and a 2 °C lower temperature constraint were' applied. There is a 38%
difference in the number of stream gaging stations, with suitable thermal habitat for
warmwater fishes, when 0 °C or 2° C is used as the lower temperature constraint.
The total number of stations with suitable thermal habitat for warmwat~r fishes is
projected not to decrease under 2XC02 climate conditions, regardless of whether a 0 °C or
a 2 °C lower temperature constraint is applied but a· northward spread of warmwater
fishes under 2XC02 climate conditions is projected. For cold-water and cool-water
fishes, the number of stations with suitable thermal habitat under a 2xC02 climate
scenario is projected to decrease by 36% and 15%, respectively, with 0 °C as the lower
temperature constraint. With a 2 °C lower temperature constraint,. more suitable habitat
for cool-water fishes and little change for cold-water fishes is projected. It is therefore
concluded that the values of the lower temperature constraint, in addition to the upper
temperature consp-aint, have a large influence on thermal habitat projections.
US Environmental Protection Agency, Mid-Continent Ecology Division and Office of Research and Development
Mohseni, Omid; Stefan, Heinz G..
Projections of Fish Survival in US Streams after Global Warming.
St. Anthony Falls Laboratory.
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