ISFAPPC01442 ‎(2)‎

• Case Number: 04CW0087
• Stream Name: Thirtyone Mile Creek
• Water Division: 2
• Water District: 12
• County: Park
• Instream Flow App - Doc Type: Supplemental Data

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DATA ANALYSIS

Interpretation of the health and integrity of the aquatic ecosystem was based
on a number of aquatic macro invertebrate indices and life history characteristics
of individual taxa and physical habitat and water chemistry data (if collected).
The indices used were those recommended for use by the u.s. Environmental
Protection Agency (82) and others (43, 44, 45, 50,53, 79). These indices should
be compared to those calculated for other sites, either impacted or non-impacted,
and be used to document changes over time at the same site. Abundance data is
shown as the number per square meter (#/m^2) for quantitative samples and the
number per sample for qualitative samples.

Community summary statistics

Richness and enumeration measures
Taxa richness - Richness is a component and estimate of community structure and
stream health based on the number of distinct taxa. Taxa richness normally
decreases with decreasing water quality (50). In some situations organic
enrichment resulta in an increase in the number of taxa, including EPT taxa (82).

Abundance - The abundance of aquatic macro invertebrates is an indicator of habitat
availability, suitability and fish food abundance. It may be reduced or increased
depending on the type of pollution.

EPT - A summary of the taxa richness within the insect orders Ephemeroptera,
Plecoptera, and Trichoptera (EPT). These orders are considered to be sensitive
to pollution. EPT generally increases with increasing water quality (53).

Family level measures - All families are separated and counted. The number and
diversity of families normally decreases with decreasing water quality (50).

Diversitv measures
Ecological diversity is a measure of community structure defined by the
relationship between the number of distinct taxa (S) and their relative
abundances (n). Washington (83) reviewed the use of diversity indices in aquatic
ecosystems and suggested the use of Simpson's 0, however, Shannon's index is widely
used and dbar has been used by the EPA (85) and the USFS (84).

Margalef's
of species
today (83)
was used.

index - Based on the presumed linear relationship between the number
and the logarithm of the number of individuals. It is seldom used
and is included for comparison to historical data where this index
It is calculated as S-l/ln(n).

Menhinick's index - This index is correlated to sample size and is not widely
used in aquatic ecology (83) and is included primarily for comparison to
historical data where this index was used. It is calculated as S/SQRT(n).

Shannon's H - Shannon's H' (47) is widely used in community ecology. It is a
measure of the average degree of uncertainty in predicting what species an
individual chosen at random from a collection of species and individuals will
belong. This average uncertainty increases as the number of species increases
and as the distribution of individuals among taxa becomes even. The higher the
number the greater the diversity. However, small cold streams have naturally low
diversity and for this reason some have criticized the use of H'.

Dbar - Dbar has been used by the EPA (85) and the USFS (84). Values range from
o to 3.32 log N. It was calculated based on the machine formula presented by
Lloyd et ale (86).