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Federal Register / Vol. 86, No. 167 / Wednesday, September 1, 2021 / Proposed Rules River, Hiwassee River, Ocoee River, Elk River, and Flint River showed some improvement during the 19992009
period, but during the 20092019
analysis period, the communities in all of the tributaries were mostly stable.
We combined the population metrics to give a population score low, medium, or high, and the habitat metrics combined to form a composite habitat score low, medium, or high.
These scores are compiled in Table 1, below. The population and habitat scores were averaged to provide the overall resilience score. Tributaries with multiple collections of several fish each
collection and multiple age classes over the 12-year period were ranked high;
conversely, those with only one collection and no evidence of reproduction were considered not established. Age classes were assigned by body length, based on life-history studies Starnes 1977, pp. 4763;
Hickman and Fitz 1978, pp. 1019.
Sites with multiple collections but only one age class were ranked low.
Tributaries with good or better IBI
scores that were stable or improving were then ranked high, and tributaries with fair IBI scores with stable or
improving conditions were ranked moderate. Overall resilience was calculated by averaging the column scores. Where snail darters had been extirpated or not established, IBI scores were not incorporated. While the habitat in Little River is very good, we found that the low numbers three or fewer individuals in any single observation of snail darters captured and the lack of multiple age classes did not warrant categorizing the Little River population as moderate or high. Our results of the tributary resiliency analysis are summarized in Table 1.

TABLE 1TRIBUTARY POPULATION RESILIENCY BASED ON COLLECTION DATA AND TVA IBI SCORES FROM 20092019
Tributary
Multiple detections
Multiple age classes
Population score
IBI
score
IBI trend
Habitat score
Holston River
French Broad River.
Little River
Citico Creek
Big Sewee Creek Hiawassee River ..
Ocoee River
South Chickamauga Creek.
Sequatchie River ..

Yes
Yes

Yes
Yes

High
High

Fair
Fair/good

Moderate
High

Moderate/high.
High.

Yes
No
No
Yes
Yes
Yes

No
No
No
Yes
Yes
Yes

Low
Not established ..
Extirpated
High
High
High

Good/excellent
Good
Poor/fair
Good/excellent
Fair
Fair

High
High
Low
High
Moderate
Moderate

Low.
Not established.
Extirpated.
High.
Moderate/high.
Moderate/high.

Yes

Yes

High

Fair

Moderate

Moderate/high.

Paint Rock River ..
Flint River
Elk River

Yes
No
Yes

Yes
No
Yes

High
Not established ..
High

Fair/good
Fair
Fair/good

High
Moderate
High

High.
Not established.
High.

Shoal Creek

No

No

Not established ..

Good

High

Not established.

Bear Creek

Yes

Yes

High

Good

Stable
Stable or improving.
Stable
Stable
Stable
Stable
Stable
Stable or declining.
Stable or declining.
Stable
Insufficient data ..
Stable or improving.
Stable or improving.
Stable or improving.

High

High.

Reservoir ResiliencyUsing the data available from the TVA snail darter trawl surveys Simmons 2019, p. 3, we analyzed resiliency of the reservoir populations based on first, the number of individuals captured; and second, evidence of reproduction, with evidence of reproduction established either through presence of multiple age classes, adults in spawning condition
gravid females and/or males flowing milt sperm, or juveniles. To categorize number of individuals, we classified collections of 04 individuals as low, 5
9 as moderate, and 10 as high. To classify reproduction, given the limited sampling effort to date, collection of more than one age class or other evidence of reproduction resulted in a high rating in the reproduction metrics.

Overall resiliency
Collection of only one age class or no other evidence of reproduction resulted in a low rating. Similar to the stream population, overall resilience was calculated by averaging the scores of the number collected and reproduction metrics. Results are summarized below in Table 2.

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TABLE 2RESERVOIR POPULATION COLLECTIONS BASED ON TVA BENTHIC TRAWLS, 20162019
Reservoir
Population score number collected
Fort Loudoun
Watts Bar
Chickamauga
Nickajack
Guntersville
Wheeler
Wilson
Pickwick

Low 2
Low 3
Low 4
High 11
High 33
High 18
Low 0
High 18

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Age classes
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2
1 2
2 2
2 0
3

Evidence of reproduction
Reproduction score
No
Yes
Yes
Yes
No
Yes
No
No

High
High
High
High
High
High
N/A
High

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Overall resilience Moderate.
Moderate.
Moderate.
High.
High.
High.
Not established.
High.

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