Monitoring Program Objectives
Habitat Variables
Habitat includes the complex of biotic and
conditions required for life,
growth, health, and reproduction of an aquatic community. Habitat variables are
an explanatory variable for a primary biological variable, but habitat variables are
also important for characterizing ecological integrity. The composition of the
biotic community may be due to the extent of species range, stocking, habitat
limitations, natural fluctuations, pollutants, other factors, or a combination of
be degraded by human activities or by natural forces. However,
these. Habitats
habitats have also been shown to respond both positively and rapidly to manage-
ment (Platts et al. 1987).
The ecological requirements for sustaining community life stages may be consid-
ered when determining habitat variables. Knowledge of the biological community
and field training are required to monitor habitat effectively and consistently.
Historical impacts are likely to influence present conditions or restoration efforts.
Important events include dam construction, unusual water level fluctuations,
grazing, channelization, dredging, or drainage of marshes. Debris snagging
(removal of branches and tree trunks to improve navigation) is also an important
habitat modification. Degradation may restrict or delay remediation.
Stream Macroinvertebrate and
Stream Macroinvertebrate and Fish Habitat. Plafkin et al. (1989) have
Fish Habitat
developed and tested methods for stream macroinvertebrate and fish habitat
evaluation. Variables for substrate, flow, channel morphology, and riparian cover
are scored by a weighted rating scheme through observation and professional
judgment. Fisheries habitat procedures
four levels of detail are provided by the
US Forest Service (USFS 1989). Aerial photos and maps provide information for
level I habitat monitoring, and ground
can verify findings. The USFS
methods (their level 2) are geomorphic and hydrologic ratings based on few
measurements. The habitat at the managed resource should be monitored along
with a reference site to determine if changes are due to impact or natural
variability.
lake and Reservoir Macroinvertebrate
Lake and Reservoir Macroinvertebrate and Fish Habitat. Although lakes and
and Fish Habitat
reservoirs share many important features, food web interactions may be distinct
in reservoirs compared to lakes and may require a different monitoring approach.
Particularly notable are the hydraulic features of lakes and reservoirs. Compared
with lakes, reservoir surface waters may not be as well mixed horizontally,
resulting in higher pollutant concentrations near inflows and a gradient along the
main stem or a tributary, with lower concentrations near the dam. Variability in
water quality can affect the food chain, habitat, physical or behavioral features in
the fish community.
Because reservoirs are more recent features of the landscape, they have less
developed predator-prey relationships. Compared with lakes, thesynchronization
in production of fish and their plankton food source may be faulty. Water level
fluctuations affect littoral habitat and food stability. Ecological systems may not
be in equilibrium, presenting some problems for assessment and the understand-
ing of complex interactions (Noble 1986).
Lake Macroinvertebrate Habitat. Variation in lake benthic communities can be
very high due to substrate type, chemistry of the sediment-water interface, vertical
migrations, wind, food availability, predation, and daily vertical migrations. The
link between water chemistry and benthic communities has not been well
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