Measures of the Health of Rivers and Streams - Hydro-Environmental Analysis: Freshwater Environments - page 203

• Indicator species metrics

• Number of intolerant or sensitive species

• Percentage of individuals that are Lepomis cyanellus (Centra rchidae)

• Trophic function metrics

• Percentage of individuals that are omnivores

• Percentage of individuals that are insectivorous Cyprinidae

• Percentage of individuals that are top carnivores or piscivores

• Reproductive function metrics

• Percentage of individuals that are hybrids

• Abundance and condition metrics

•

Abundance or catch per effort of ish

• Percentage of individuals that are diseased, deformed, or have eroded ins, lesions, or

t umors (DELTs).

In the original IBI, each metric received a score of:

• Five points: for a value similar to that expected for a ish community characteristic of a

system with little human inluence.

• One point: for a value similar to that expected for a ish community that departs signii-

cantly from the reference condition.

• Three points: for an intermediate value.

A cumulative score was determined, ranging from 0 (usually 12 is considered the “worst”) to 60
(best), which was then used as an indicator of the degree of human disturbance.
More recent IBIs have generally retained the original metrics but they have been modiied to
relect conditions in particular geographic regions or states. Kerans and Karr (1994) also demon-
strated the use of a benthic IBI that includes metrics based on benthic macroinvertebrates, which
was applied to rivers in the Tennessee Valley.
Generally, the applications of speciic organizations today start with the available and documented
metrics (see, for example, the U.S. EPA website on metrics and the IBI; Simon and Lyons [1995] and
select the applicable metrics). The metrics are then standardized to a numeric scale, from worst to best.
Once the metrics are scored, they can then be used as a measure of the condition of the waterbody.
An example is provided in Table 7.4 for California streams and rivers (Harrington and Born 1999).
Another example is the M-BISQ methodology in Mississippi (MDEQ 2003), an IBI for
Mississippi freshwater wadeable streams based on benthic macroinvertebrates. Formerly, the state
of Mississippi used water quality criteria to determine water quality impairments as required under
Section 303(d) of the CWA; that is, a list of waterbodies of the state that are not meeting water qual-
ity standards. The dificulty, as described previously, is having suficient water quality data to sup-
port or determine the listing. An alternative that was implemented by the Mississippi Department
of Environmental Quality was the determination of aquatic health or biotic integrity based on
a biological rather than a chemical monitoring plan, under the assumption that biota integrates
impacts, which, if less than some criteria, can be used to list waters that are impaired. Developing
the M-BISQ (MDEQ 2003) involved the following steps:

1. Develop a database

2. Delineate preliminary site classes

3. Develop criteria for the designation of least and most disturbed sites

4. Calculate metrics

5. Delineate inal site classes

6. Test metrics

7. Develop index