River Ecology and Restoration - River Dynamics and Integrated River Management - page 665

measure a species' response to its habitat can influence the outcome of the investigation. As van Horne
(1983) pointed out, density or number of fish may be misleading indicators of habitat quality. Fish
response guilds as indicators of restoration success in riparian ecosystems may be a valuable monitoring
tool.
Hocutt (1981) states “perhaps the most compelling ecological factor is that structurally and functionally
diverse fish communities both directly and indirectly provide evidence of water quality in that they
incorporate all the local environmental perturbations into the stability of the communities themselves.”
The advantages of using fish as indicators are: (1) they are good indicators of longterm effects and broad
habitat conditions; (2) fish communities represent a variety of trophic levels; (3) fish are at the top of the
aquatic food chain and are consumed by humans; (4) fish are relatively easy to identify; and (5) water
quality standards are often characterized in terms of fisheries. However, using fish as indicators is
inconvenient because: (1) the cost of collection is high; (2) long term monitoring and a large number of
samplings are needed to have reliable results and statistical validity may be hard to attain; and (3) the
process of sampling may disturb the fish community.
Electrofishing is the most commonly used field technique. Each collecting station should be
representative of the study reach and similar to other reaches sampled; effort between reaches should be
equal. All fish species, not just game species, should be collected for the fish community assessment.
Karr et al. (1986) used 12 biological metrics to assess biotic integrity using taxonomic and trophic
composition and condition and abundance of fish. The assessment method using fish as indicator has
been studied and applied in many large rivers (Plafkin et al., 1989).
10.3.1.4 Birds and Mammals
Birds and mammals are used as indicator species for both terrestrial and aquatic ecosystems. Croonquist
et al. (1991) evaluated the effects of anthropogenic disturbances on small mammals and birds along
Pennsylvania waterways. They evaluated species in five different response guilds, including wetland
dependency, trophic level, species status (endangered, recreational, native, exotic), habitat specificity,
and seasonality. The habitat specificity and seasonality response guilds for birds were best able to
distinguish those species sensitive to disturbance from those, which were not affected or benefited. Edge
and exotic species were greater in abundance in the disturbed habitats and might serve as good indicators
there. Seasonality analysis showed migrant breeders were more common in undisturbed areas, which, as
suggested by Verner (1984), indicate the ability of guild analysis to distinguish local impacts.
In general the advantages of using birds and mammals as indicator species are: (1) they are good
indicators of long-term effects and broad habitat conditions, including terrestrial and aquatic ecosystems;
(2) they are at the top of the food chain; (3) they are relatively easy to identify; and (4) some restoration
projects aim at restoration of endangered birds and mammals. The disadvantages are: (1) the cost of
collection is high; (2) long term monitoring is needed to have reliable results; and (3) they are not sensitive
to aquatic habitat conditions (e.g., hydrological changes or water pollution). Birds have been used as
indicator species for ecological assessment of wetlands.
10.3.1.5 Algae
Algae communities are also useful for bioassessment. Algae generally have short life spans and rapid
reproduction rates, making them useful for evaluating short-term impacts. Sampling impacts are minimal
to resident biota, and collection requires little effort. Primary productivity of algae is affected by physical
and chemical impairments. Algal communities are sensitive to some pollutants that might not visibly
affect other aquatic communities. Algal communities can be examined for species, diversity indices,
species richness, community respiration, and colonization rates. A variety of nontaxonomic evaluations,
such as biomass and chlorophyll, may be used and are summarized in Weitzel (1979). Rodgers et al. (1979)