Monitoring Program Objectives
Biotic interactions may determine extent or absence of a species or community
independent of environmental quality or management. These interactions may be
important for tracking the effects of pollutants or controls on fish populations.
Other interactions to consider are competition, predation, disease, and parasitism.
Energy and organic matter processing in the stream ecosystem. Organic
energy sources for stream fauna of terrestrial origin include leaves, branches, tree
trunks, other organic matter, and algae. The process of organic matter generation
and cycling regulates food availability, which in turn helps structure the stream
community. Species and groups of benthic macroinvertebrates are specialized in
their ability to consume organic matter for a given particle. Empirical studies of
the fisheries habitat quality and community attributes may be used as aids in
size, type, and origin
determination of variables (Oswood and Barber
(Minshall et al. 1985).
Lake and Reservoir Fish Habitat Evaluations. Few methodologies are
able for the assessment of lake habitat quality. Critical conditions to consider are
reproduction, hiding, and food in each identified habitat zone.
Lake habitat zones are typically demonstrated by depth and by the presence or
absence of vegetation attached to the bottom. A simplified cross-sectional view of
lake habitat zones is given in Figure 3.4. A lake may be divided into three zones:
the littoral, pelagic, and profundal. The littoral zone extends from the shoreline
toward the open water to the point where the bottom becomes devoid of
vegetation. The pelagic zone is the free open water exclusive of the littoral zone.
Below the pelagic zone is the profundal zone which, if it exists, is devoid of
Littoral Zone. The shallow area around the perimeter of the lake, which can
extend to the middle of shallow lakes, supports a wide range of heterogeneous and
patchy habitats. Littoral flora may also include wetland species of macrophytes
and periphyton. Production by this group of plants can be substantial and can
exceed that of the open-water pelagic zone. Lake bottom characteristics may in
part determine the species composition of macrophyte stands. Light availability
is important for regulating macrophyte species production and composition
(Wetzel 1983). In turn, macrophyte and periphyton production may influence
chemical and physical properties of the lake as well as tht composition, and
production of insects, larger invertebrates, and fish. While more studies are
needed, fisheries managers will benefit from evaluating littoral habitat composi-
tion and function.
Pelagic Zone. The habitat of the pelagic zone is generally more homogeneous and
less patchy compared with the littoral zone, although gradients and discontinuities
are common. This open-water surface layer of lakes produces free-floating algae
called phytoplankton. The health or condition of a lake may be measured by
phytoplankton speciescomposition orbiomass. Lake response to reduced nutrient
loading is first expected in the phytoplankton community. However, inhibiting
factors such as food-web interactions between phytoplankton, zooplankton, and
fish, for example, can mask the effect of controls. Therefore, food web compo-
nents and their variability should measure ecosystem impact.
Profundal Zone. Compared with the littoral zone, the profundal zone is more
homogeneous and generally contains fewer benthic animal
zone is essentially devoid of light and photosynthetic activity. Particulate matter
(plankton, detritus) from the pelagic zone falls through the water column into the