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Federal Register / Vol. 86, No. 246 / Tuesday, December 28, 2021 / Proposed Rules Status of the North Feather DPS and Central Coast DPS of the Foothill Yellow-Legged Frog Throughout All of Their Ranges We have carefully assessed the best scientific and commercial information available regarding the past, present, and future threats to the North Feather and Central Coast DPSs of the foothill yellow-legged frog and their habitat.
Below we summarize our assessment of status of the North Feather DPS and Central Coast DPS under the Act.
North Feather DPS: Numerous threats are currently acting on the North Feather DPS. The North Feather DPS is within the most hydrologically altered part of the foothill yellow-legged frogs range Factor A and potentially is among the most impacted by the latent effects from historical mining Hayes et al. 2016, pp. 5354 Factor A. Other threats to the DPS include nonnative species bullfrogs and crayfish Factor C, impacts to habitat agriculture, urbanization, severe wildfire Factor A, recreation Factor E, the effects of climate change Factor E, and inadequacy of regulatory mechanisms Factor D. After evaluating threats to the DPS and assessing the cumulative effect of the threats under the Acts section 4a1 factors, we conclude that under current conditions, resiliency, redundancy, and representation for the North Feather DPS are reduced.
The North Feather DPS occupies a relatively small area and several streams or occurrences have been extirpated from past impacts eastern portion of range, southwestern area near Lake Oroville, and some occurrences in northern Butte County CDFW 2020, dataset, entire; Service 2021, figure 49, p. 131. The North Feather DPS also has the highest average relative risk of population decline with only 16 15
percent of the 109 analyzed stream segments in the low risk category and 34
stream segments 31 percent in the high risk category. Overall abundance of foothill yellow-legged frogs for the North Feather DPS is largely unknown, but egg mass densities are very low in the two regulated stream reaches that have long-term monitoring Rose et al.
2020, pp. 6364, table 1. For example, sections of the Cresta reach of the North Feather River that historically had relatively high numbers of foothill yellow-legged frog egg masses did not have egg masses or were extremely reduced for several years 20062017
CDFW 2019, p. 31; Dillingham 2019, p.
7.
Under current conditions, resiliency in the North Feather DPS is reduced, largely because of the DPSs occupation
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of a small geographic area, range contraction, the relatively high risk of the DPSs decline, and the areas high degree of hydrological alteration.
However, the North Feather DPS still currently contains a relatively high proportion of occurrence records with 42 percent of all known occurrences being from the 20102020 timeframe Service 2021, table 10, figure 49, pp.
125, 131. As a result, occupancy for the North Feather DPS is good, based on a majority of records being within the 20002020 timeframe, but abundance is low where there has been population monitoring. Current redundancy is limited in the North Feather clade. The North Feather DPS not only occupies the smallest area, but its occupied stream segments are not well-distributed over the geographical area it occupies.
Current representation of the DPS is most likely reduced due to past loss of populations.
In 2001, the FERC issued an order to the licensee responsible for flow regulation on the Cresta and Poe reaches of the North Feather River Rock Creek Cresta Hydroelectric Project FERC
Project No. 1962 Pacific Gas and Electric Company PG&E. The order required PG&E to develop a plan to ensure recreational and pulse flow releases did not negatively impact the foothill yellow-legged frog. The order also required the establishment of an Ecological Resources Committee ERC
to evaluate effects of flows and provide adaptive management strategies if flows had a negative impact on the foothill yellow-legged frog populations within the two reaches. In 2006, flow releases for recreational boating were discontinued on the Cresta reach due to possible impacts from flows resulting in low foothill yellow-legged egg masses that year. In 2009 and again in 2014, modified flow programs were implemented to mimic natural flow regimes by reducing flows in spring and summer April through the foothill yellow-legged frogs breeding season GANDA 2018, pp. 12. We expect these measures to continue due to the establishment of the ERC on monitoring impacts to foothill yellow-legged frog populations on the two reaches. As a result, there are some signs of improved abundance since 2018, in the Cresta reach of the North Feather River following the above described modifications of the regulated flow regime to more natural conditions.
Additional conservation efforts have been implemented to improve abundance of the North Feather DPS
including in-situ and ex-situ rearing of foothill yellow-legged frogs for
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reintroduction GANDA 2018, pp. 13, 13, table 2; Dillingham 2019, pp. 79;
Rose et al. 2020, pp. 6364, 76, table 1, figure 4. The Forest Service has noted habitat improvements in breeding areas of the Cresta reach and expects abundances and breeding activity to continue to increase in response to conservation efforts associated with insitu and ex-situ rearing efforts Dillingham 2019, pp. 79. In addition, the environmental condition of streams in the range of the North Feather DPS
exhibit colder stream temperatures.
These cooler water temperatures, although not currently preferable for the foothill yellow-legged frog, may help to provide climatic resiliency during periods of hot weather that may increase stream temperatures and may extend breeding and rearing timeframes. In addition, the existing conservation efforts to improve populations and regulatory measures to benefit habitat conditions as described above currently document improvements to the DPSs overall current condition. After evaluating threats to the species and assessing the cumulative effect of the threats under the section 4a1 factors, we have determined that despite the current condition of the DPS being reduced, the population and habitat factors used to determine the resiliency, representation, and redundancy for the DPS have not been reduced to such a degree to consider the North Feather DPS currently in danger of extinction throughout its range.
However, threat conditions in the future are likely to substantially impact populations of the North Feather DPS.
Because of the current cold stream temperatures, future climatic conditions that may increase stream temperatures may potentially benefit many of the North Feather DPS populations;
however, the negative effects of increases in streamflow variability due to climate change i.e., drought/flood events, snow/rain events and residual environmental stochasticity likely outweigh the benefit of any warmer stream temperatures. Increased water demand and anticipated additional regulation to an already highly regulated hydrologic condition of the DPSs habitat will further limit the DPSs capability to maintain adequate population sizes to support the DPSs metapopulation structure. Nonnative species bullfrogs and crayfish will continue to impact the DPS and their impacts may increase as temperatures warm, allowing for spread of warm water species such as bullfrogs and smallmouth bass. Trends indicate that the amount of area severely burned annually by wildfires has been
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