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Federal Register / Vol. 86, No. 167 / Wednesday, September 1, 2021 / Proposed Rules
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Evaluating Populations There is not currently enough information available to determine population size for the snail darter. Few targeted surveys have been conducted for snail darters since the species was downlisted to threatened in 1984.
Stream community monitoring is conducted by TVA throughout the Tennessee River basin using an index of biotic integrity IBI approach. The IBI
uses fish community metrics, such as percent insectivore, to develop a score of stream health. These surveys are targeting a representative sample of the overall fish assemblage rather than individual species, so are not designed to provide population size information on rare species, but are useful for determining species persistence at a site. Occasional encounters by IBI
monitoring crews provide information in the intervening years, but many of these surveys took place in wadeable portions of streams, missing the deeper water habitats often used by the species.
Where snail darters are common near IBI sites, surveyors intentionally avoid their habitat to reduce the probability of injury, which can result in artificially reduced numbers of the species in samples. The wide variety of methods used during previous survey efforts also makes comparing populations difficult.
Records from snorkel surveys targeted at other species only note incidental sightings of snail darters, not density, and the TVA trawls have mostly been carried out to determine the species presence and range Simmons 2019, p.
1. However, it is likely that reproducing populations of the species exist in at least 16 locations 6 reservoirs and 10
tributaries based on repeated collections that have been made at those locations, evidence of multiple age classes at those locations i.e., suggesting regular recruitment into the population, and multiple males and females captured at those locations see Tables 1 and 2 in Summary of Biological Status, below.
Recovery Section 4f of the Act directs us to develop and implement recovery plans for the conservation and survival of endangered and threatened species unless we determine that such a plan will not promote the conservation of the species. Recovery plans must, to the maximum extent practicable, include objective, measurable criteria which, when met, would result in a determination, in accordance with the provisions of section 4 of the Act, that the species be removed from the list.

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Recovery plans provide a roadmap for us and our partners on methods of enhancing conservation and minimizing threats to listed species, as well as measurable criteria against which to evaluate progress towards recovery and assess the species likely future condition. However, they are not regulatory documents and do not substitute for the determinations and promulgation of regulations required under section 4a1 of the Act. A
decision to revise the status of a species, or to delist a species is ultimately based on an analysis of the best scientific and commercial data available to determine whether a species is no longer an endangered species or a threatened species, regardless of whether that information differs from the recovery plan.
There are many paths to accomplishing recovery of a species, and recovery may be achieved without all of the criteria in a recovery plan being fully met. For example, one or more criteria may be exceeded while other criteria may not yet be accomplished. In that instance, we may determine that the threats are minimized sufficiently and that the species is robust enough that it no longer meets the definition of an endangered species or a threatened species. In other cases, we may discover new recovery opportunities after having finalized the recovery plan. Parties seeking to conserve the species may use these opportunities instead of methods identified in the recovery plan.
Likewise, we may learn new information about the species after we finalize the recovery plan. The new information may change the extent to which existing criteria are appropriate for identifying recovery of the species.
The recovery of a species is a dynamic process requiring adaptive management that may, or may not, follow all of the guidance provided in a recovery plan.
The snail darter recovery plan Service 1983, entire included recovery criteria to indicate when threats to the species have been adequately addressed and prescribed actions that were thought to be necessary for achieving those criteria. Below, we discuss our analysis of available data and our determination as to whether recovery criteria for the snail darter have been achieved.
Recovery Criteria The objective of the recovery plan is to protect and recover the snail darter to the point where it can be removed from the Federal List of Endangered and Threatened Wildlife. The recovery plan states that the species shall be
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considered recovered when one of the alternatives A, B, or C listed below is met and no present or foreseeable threats exist that could cause the species to become in danger of extinction Service 1983, p. 27.
Alternative A: Suitable habitat areas of the Tennessee River within the area from the backwaters of Wheeler Reservoir upstream to the headwaters of Watts Bar Reservoir are inhabited by snail darter populations that can survive and reproduce independently of tributary rivers as evidenced by documented reproduction in Watts Bar Reservoir or some other Tennessee River reservoir.
Alternative B: More Tennessee River tributary populations of the species are discovered and existing populations are not lost. The number of additional populations needed to meet this criteria would vary depending on the status of the new populations, but two populations similar to the Big Sewee Creek, South Chickamauga Creek, or Sequatchie River populations, or one comparable to the Hiwassee River population, would denote recovery.
Alternative C: Through maintenance of existing populations and/or by expansion of these populations, there exist viable populations of snail darters in five separate streams such as Big Sewee Creek, Hiwassee River, South Chickamauga Creek, Sequatchie River and Paint Rock River. For this alternative, viable populations means that population monitoring over a 10year period biannual sampling indicates that the snail darter is reproducing at least two year classes present each year sampled and that the population is either stable or expanding.
For some populations, existing data may be used to meet this requirement.
Achievement of Recovery Criteria Alternative A of the recovery criteria requires that snail darters be present in suitable habitats within reservoirs from Wheeler Reservoir upstream to Watts Bar Reservoir and evidence of reproduction within reservoirs independent of tributaries in at least one reservoir. We conclude that Alternative A has been met based on collection of seven permanent mainstem populations Pickwick, Wheeler, Guntersville, Nickajack, Chickamauga, Watts Bar, and Fort Loudoun reservoirs and evidence of reproduction independent of tributaries in Chickamauga, Nickajack, and Wheeler reservoirs see Tables 1
and 2 in Summary of Biological Status, below, and Figure 1 in Background, above. These populations represent
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