GLOBAL WARMING AND POTENTIAL CHANGES IN FISH HABITAT
IN U.S. STREAMS
, HEINZ G. STEFAN
and JOHN G. EATON
University of Minnesota, St. Anthony Falls Laboratory, Mississippi River at 3rd Ave. SE,
Minneapolis, MN 55414, U.S.A.
E-mail: firstname.lastname@example.org and email@example.com
Formerly U.S. Environmental Protection Agency, Mid-Continent Ecology Division,
Duluth, MN, U.S.A.
Abstract. To project potential habitat changes of 57 ﬁsh species under global warming, their suitable
thermal habitat at 764 stream gaging stations in the contiguous United States was studied. Global
warming was speciﬁed by air temperature increases projected by the Canadian Centre of Climate
Modelling General Circulation Model for a doubling of atmospheric CO
. The aquatic 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 max-
imum temperature and minimum temperature tolerances. For cold water ﬁshes with a 0
temperature constraint, the number of stations with suitable thermal habitat under a 2 × CO
scenario is projected to decrease by 36%, and for cool water ﬁshes by 15%. These changes are
associated with a northward shift of the range. For warm water ﬁshes with a 2
C lower temperature
constraint, the potential number of stations with suitable thermal habitat is projected to increase by
Fish habitat in streams may be characterized by several interdependent factors,
which include water temperature, streamﬂow, channel structure and food web
relationships (Rundquist and Baldrige, 1990). If water temperature exceeds the
maximum temperature tolerance of a ﬁsh species, the ﬁsh species is likely to be
absent or disappear from that stream reach (Eaton and Scheller, 1996). Under po-
tential global warming due to an increase of carbon dioxide and other greenhouse
gases in the atmosphere, the thermal regimes of streams would change. It is quite
likely that the higher water temperatures would exceed the maximum temperature
tolerances of some ﬁsh species.
Studies of the potential effects of climate warming on ﬁsh thermal habitat in
streams were previously conducted by Coutant (1990), Magnuson et al. (1990),
Stefan et al. (1995), Rahel et al. (1996) and others. Eaton and Scheller (1996) were
among the ﬁrst to estimate ﬁsh habitat responses to climate change over the entire
contiguous United States. They projected maximum weekly stream temperatures
at 1,776 stream gaging stations by assuming a linear relationship between stream
temperature and air temperature increases. The slope of the linear relationship was
Climatic Change 59: 389–409, 2003.
© 2003 Kluwer Academic Publishers. Printed in the Netherlands.