1. Living aquatic communities are largely determined and maintained by the volume
and quality of flowing waters, both within lotic systems and in receiving waters
of coastal systems. However, flow is one of the most frequently and extensively
altered features of rivers and streams; alteration effects are likely to be exacerbated
by climate change. Lotic systems vary and different fish species need different
environmental conditions, and distinct problems are evident at various
spatial scales. New synoptic flow and biological information now make it possible
to evaluate the effects of altered flows throughout the Great Lakes Region at
scales from the stream reach to the Region.
2. We used estimates of river and streamflow and observed fish abundances to
develop tools that specify the response of fish to alterations in those flows. We
fit the logistic model to a cumulative fish abundance curve as a function of yield
providing an empirical means to develop models of the response of cumulative
fish abundance to flows.
3. Response zones of yield for each species in each system type (based on size and
thermal class) illustrate how criteria may be developed that can be used in decision-
making for management of flows. In our example application, we evaluate
both the general response of brook trout (Salvelinus fontinalis) abundances (and
fish diversity) to changes in flows and assess the sensitivity of each stream fish
community to flow alteration. Mapping stream sensitivity to flow alteration
throughout the US Great Lakes Region with a multiscale spatial framework
showed how regional variability in sensitivity for any fish species or assemblage
may be evaluated and provides managers with information to help determine
where the best opportunities for protection or restoration of streamflows and
associated communities exist.
4. These results provide valuable tools and critical information to managers responsible
for balancing water uses and maintaining high quality lotic ecosystems. These
methods may be applied to any geographic region and can be extended nationally
or globally, where flow, temperature, fish and landscape data are available.
Additional publication details
Measuring and evaluating ecological flows from streams to regions: Steps towards national coverage
Great Lakes Science Center
Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, Wisconsin