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Federal Register / Vol. 86, No. 167 / Wednesday, September 1, 2021 / Proposed Rules multiple reservoirs, rivers and span at least three physiographic regions Highland Rim, Cumberland Plateau, and Ridge and Valley Etnier and Starnes 1993, p. 3; Mettee et al. 1996, p.
5.
Our assessment of the tributary populations of snail darters supports the determination that Alternative B has also been met. Alternative B of the recovery criteria requires the discovery or establishment of at least two new tributary populations similar to the Big Sewee Creek, South Chickamauga Creek, or Sequatchie River populations or one comparable to the Hiwassee River population. In our analysis, we determined that 10 tributary populations are extant that have a moderate or high resilience see Table 1, below. Four of these French Broad River, Ocoee River, Elk River, and Bear Creek have been found or established since the recovery plan was finalized.
The largest new population occurs in the lower French Broad River. The founders of this population were likely migrants or juveniles from the stocked population in the Holston Service 2013, p. 14. Snail darters have been collected across at least 21.8 miles 35.1 km of the French Broad River and across 19
miles 30.5 km of the Hiwassee River Ashton and Layzer 2008, pp. 5455;
Kuhajda 2018, supplementary data;
TVA, unpublished data. Therefore, the requirement to discover or establish a population comparable to the Hiwassee River population has been met.
Additionally, Alternative B gives the option of two tributary populations comparable to Big Sewee Creek, South Chickamauga Creek, and Sequatchie River. The current populations in the Ocoee River and Bear Creek are comparable to the Big Sewee Creek, South Chickamauga Creek, and Sequatchie River populations at the time the recovery plan was finalized based on captures and occupied stream length.
Since 2011, snail darters have been found consistently in the Ocoee River by TVA IBI crews, appearing in every biannual sample since 2015. Snail darters have been collected across 5.9
miles 9.5 km of the Ocoee River, and collections of snail darters in the Hiwassee River near the mouth of the Ocoee suggests that they may occupy more of the river.
Snail darters have only been collected as individuals or pairs, but the lower portion of Bear Creek is in the Gulf Coastal Plain physiographic region, so preferred habitat is more limited than in other streams. Individuals have been collected across 5.8 miles 9.3 km of Bear Creek, but trawling collections near
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the mouth of Bear Creek and eDNA
detections in the lower parts of the Bear Creek system and at its mouth suggest that snail darters may occur in an additional 25 miles 40 km of the creek Simmons 2019, supplementary data;
Shollenberger 2019, pp. 1416.
Since 2015, snail darters have been collected in 1.4 miles 2.3 km of the Elk River in Tennessee. Snail darters may also occur in the Alabama portion of the Elk River over more than 20 river miles of free-flowing stream down to the portion of the river inundated by Wheeler Reservoir Simmons 2019, supplementary data; Shollenberger 2019, pp. 1416.
In summary, our assessment of the tributary populations of the snail darter supports the determination that Alternative B has been met based on the establishment of the French Broad River population that is comparable to the Hiwassee population. Additionally, the Ocoee River, Bear Creek, and Elk River populations are comparable to the Big Sewee Creek historical population, which was found across 4.2 miles of stream, exceeding the prescription in Alternative B for at least one additional large population or two additional small populations.
Alternative C has been partially met.
This alternative of the recovery criteria calls for the maintenance of viable populations in five separate streams.
The definition for viable populations in the 1983 recovery plan requires biannual monitoring over a 10-year period with enough data to demonstrate a stable or increasing population size and evidence of reproduction indicated by the presence of at least two year classes present in each year sampled.
We do not have sufficient specific monitoring data to meet this definition since most of our collections come from TVA IBI surveys that are not speciesspecific. However, our analysis of the tributary populations found 10
populations that were considered at least moderately resilient see Table 1 in Summary of Biological Status, below.
Of these, nine met the requirement of Alternative C that at least two year classes be present. The discovery of populations in Bear Creek, Elk River, Wheeler Reservoir, and Pickwick Reservoir since 2009 shows evidence of either species expansion, or growth of existing populations to the level of detection see Table 2 in Summary of Biological Status, below. The presence of resilient populations in 10 tributaries and 7 mainstem reservoirs across four physiographic regions provides evidence of high redundancy and representation for the species see
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further explanation of these terms in Analytical Framework, below.
Regulatory and Analytical Framework Regulatory Framework Section 4 of the Act 16 U.S.C. 1533
and its implementing regulations 50
CFR part 424 set forth the procedures for determining whether a species is an endangered species or a threatened species. The Act defines an endangered species as a species that is in danger of extinction throughout all or a significant portion of its range, and a threatened species as a species that is likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range. The Act requires that we determine whether any species is an endangered species or a threatened species because of any of the following factors:
A The present or threatened destruction, modification, or curtailment of its habitat or range;
B Overutilization for commercial, recreational, scientific, or educational purposes;
C Disease or predation;
D The inadequacy of existing regulatory mechanisms; or E Other natural or manmade factors affecting its continued existence.
These factors represent broad categories of natural or human-caused actions or conditions that could have an effect on a species continued existence.
In evaluating these actions and conditions, we look for those that may have a negative effect on individuals of the species, as well as other actions or conditions that may ameliorate any negative effects or may have positive effects.
We use the term threat to refer in general to actions or conditions that are known to or are reasonably likely to negatively affect individuals of a species. The term threat includes actions or conditions that have a direct impact on individuals direct impacts, as well as those that affect individuals through alteration of their habitat or required resources stressors. The term threat may encompasseither together or separatelythe source of the action or condition or the action or condition itself.
However, the mere identification of any threats does not necessarily mean that the species meets the statutory definition of an endangered species or a threatened species. In determining whether a species meets either definition, we must evaluate all identified threats by considering the species expected response and the
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