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Federal Register / Vol. 86, No. 162 / Wednesday, August 25, 2021 / Proposed Rules species is extirpated from a large portion of its range, including the entire Upper Amur unit and several major tributaries.
High-resilience units are those in a self-sustaining condition and experiencing little, if any, risk of extirpation; they have relatively higher abundance of adult females, connectivity between feeding and spawning grounds, high water quality, and fish survive to reproduce multiple times. Moderate-resilience units are unlikely to be self-sustaining and are experiencing some level conservation threat that could eventually lead to extirpation. Lowand very-lowresilience units are not self-sustaining, due to ongoing conservation threats;
they may become extirpated, perhaps rapidly in the case of very low-

resilience units. Highly redundant species have a large number of populations, which safeguards against rare, localized catastrophic events.
Representation is a measure of the species capacity to adapt to changing environments.
The species as a whole is estimated to have experienced a population decline of greater than 95 percent between 1960
and 2010 Ruban and Qiwei 2010, not paginated. However, using a 1960
baseline underestimates actual historical declines in the species abundance because intense fishing occurred at least as early as the 1890s Koshelev et al. 2016, p. 240; Vaisman and Fomenko 2006, p. 11. Sizeable populations now exist only in the Amur Estuary and Lower Amur analysis units Koshelev et al. 2014a, pp. 13131316.

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The species has a skewed sex ratio of 1
female per 2 males, very likely due to preferential poaching of females for caviar and use in aquaculture Koshelev et al. 2014b, pp. 1127, 1129, and the largest fishwhich are also the most reproductively valuablehave been removed from the population Koshelev et al. 2014a, table 5.
Our assessment of the resilience of each of the three extant analysis units indicates that none are in self-sustaining condition see table 2, below. Only the Amur Estuary unit has even moderate resilience. Details of how we determined overall resilience from the four demographicand habitat-based criteria in table 2, below, can be found in the SSA report.

TABLE 2CURRENT RESILIENCE OF THE THREE EXTANT AMUR STURGEON ANALYSIS UNITS
Resilience criteria
Amur Estuary
Lower amur
Middle amur
Number of reproductive females
Water quality to support prey availability and sturgeon health.

28,860
Receives water pollution from all upstream reaches, including the heavily polluted Songhua and Lower Amur.
May impact sturgeon health and prey abundance.

425
Heavy industrial presence and human population density.
Likely impacts sturgeon health and prey abundance.

Survival times.

High fishing pressure
Estimated 95 percent of spawning fish captured annually.
Size of captured fish and proportion of fish that are large females are declining.
Limits average fecundity
No dams. Fish can move into the main stem of the river to reach spawning grounds.

High fishing pressure
Estimated 95 percent of spawning fish captured annually.
Size of captured fish and proportion of fish that are large females are declining.
Limits average fecundity
No known barriers to connectivity
Nearly extirpated.
Songhua River includes the most polluted sections of the Amur basin.
The medium-sized cities of Heihe and Blagoveschensk deposit sewage and industrial waste into this reach of the Amur.
Likely impacts sturgeon health and prey abundance.
Few reproductive fish present.
Fishing pressure is likely still very high for any fish present.

Moderate

Low

to
reproduce
Connectivity between and feeding grounds.

multiple
spawning
Current Resilience

Songhua, Nen, Zeya, and Bureya River dams prevent fish from reaching spawning sites. Main stem remains without obstructions.
Very low.

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Note: Sources for the information in this table are Koshelev et al. 2014a, pp. 13101316; Koshelev et al. 2014b, p. 1127; Cai et al. 2013, p.
150; Ruban and Qiwei 2010, not paginated; Simonov and Dahmer 2008, p. 47; Novomodny et al. 2004, p. 18; and others provided in the SSA
reports detailed discussion of current condition.

Amur sturgeon redundancy is considerably reduced compared to its historical level, which was never high, given that the species is endemic to a single large river system. One of four units the Upper Amur is extirpated, and the Middle Amur unit is on the brink of extirpation, too. The Amur sturgeon has been extirpated from several major tributaries e.g., the Zeya and Bureya within the Middle and Lower Amur units. Despite the species low redundancy, we assess that its geographically dispersed nature, across a several-hundred km stretch of the Lower Amur and Estuary, means that
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complete extinction of the population due to a single catastrophic event is unlikely, at present.
We have very little information about the contemporary population genetic structure of wild Amur sturgeon, making it difficult to fully assess the species representation. However, we can assess that the variety of ecological settings inhabited by Amur sturgeon is at least somewhat reduced in the last century as the geographic range of the species has contracted to primarily the Lower Amur and Amur Estuary, now excluding the Upper Amur, as well as the Zeya, Bureya, and Songhua Rivers,
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all tributaries of the Amur. In turn, we expect that adaptive potential of the species is also lower than before, although we cannot quantify this at present.
We note that, by using the SSA
framework to guide our analysis of the scientific information documented in the SSA report, we have not only analyzed individual effects on the species, but we have also analyzed their potential cumulative effects. We incorporate the cumulative effects into our SSA analysis when we characterize the current and future condition of the species. To assess the current and future
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