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Federal Register / Vol. 86, No. 162 / Wednesday, August 25, 2021 / Proposed Rules The SSA report represents a compilation of the best scientific and commercial data available concerning the status of the species, including the impacts of past, present, and future factors both negative and beneficial affecting the species. The Service sent the SSA report to six independent peer reviewers and received one response.
Proposed Listing Determination Background A thorough review of the taxonomy, life history, ecology, and overall viability of the Amur sturgeon is presented in the SSA report Service 2020; available at http
www.regulations.gov. The following discussion is a summary of the biological background on the species from the SSA report.
Taxonomy The Amur sturgeon Acipenser schrenckii is one of 27 species of sturgeon in the family Acipenseridae Fricke et al. 2019, not paginated. The synonyms Acipenser schrenki and Acipenser schrenkii are sometimes used, but are now considered invalid Fricke et al. 2019, not paginated; ITIS
2019, not paginated. We are not aware of any taxonomic disputes regarding the validity of the Amur sturgeon as a species. Thus, we determined that the Amur sturgeon is a valid species for listing under the Act.

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Physical Description Amur sturgeon are large fish reaching up to 3 meters m 10 feet in length and 190 kilograms 420 pounds in weight Zhuang et al. 2002, p. 659.
They have a downward-facing mouth, cartilaginous skeleton, and a series of bony plates in rows along their back Billard and Lecointre 2001, p. 363.
Tactile barbels hang from the mouth Billard and Lecointre 2001, p. 359. A
rare brown morph of Amur sturgeon grows more slowly than the more common gray morph Zhuang et al.
2002, p. 660. The presence of two color morphs Zhuang et al. 2002, p. 660;
Krykhtin and Svirskii 1997, p. 236
indicates some level of ecological or genetic diversity in the Amur sturgeon.
Range Amur sturgeon live in the Amur River basin along the far eastern border between China and Russia. The species range includes the main river, its tributaries, and the Amur Estuary. The species was historically found as far west as Nerschinsk, Russia, in the upper Shilka River Georgi 1775 cited in Vaisman and Fomenko, p. 4 and in all major tributaries of the Amur. Amur
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sturgeon are rare in areas of the estuary with salinity over 7.5 parts per thousand ppt Koshelev et al. 2014a, p. 1314.
The species occurs at low densities in the southern and possibly northern Sea of Okhotsk. Very rarely, Amur sturgeon are found in the Sea of Japan Koshelev et al. 2014a, p. 1313. The species may also be present in very small numbers in Lake Khanka in extreme southeast Russia Ruban and Qiwei 2010, not paginated, although few authors confirm this.
Life History Amur sturgeon are slow to mature;
males require 7 to 12 years, and females 9 to 14 years, before reproducing Novomodny et al. 2004, p. 19; Zhuang et al. 2002, p. 659. This long time to maturity can slow the species recovery from disturbance, relative to that of species with shorter generation times.
On reaching maturity, fish are between 1.1 and 1.3m 43 to 51 in long and weigh 6 to 19 kg 13 to 42 pounds;
Zhuang et al. 2002, p. 660. Individuals can live up to 60 years Krykhtin and Svirskii 1997, p. 236 and reproduce every 3 to 4 years Ruban and Qiwei 2010, not paginated; Vaisman and Fomenko 2006, p. 5; Krykhtin and Svirskii 1997 p. 236.
Spawning adults migrate upstream, mostly in spring Koshelev et al. 2014b, p. 1126; Zhuang et al. 2002, p. 659;
Krykhtin and Svirskii 1997, p. 237; Wei et al. 1997, p. 245. A smaller number of reproductive fish migrate the previous fall mid-August to late September and overwinter on the spawning grounds Ruban 2020, pers.
comm..
The exact distance that fish move upstream is unclear, although fish appear to spawn within the same river regions lower, middle, upper as those in which they spend the rest of the year Ruban and Qiwei 2010, not paginated;
Novomodny et al. 2004, p. 18. Few migrations are greater than 500
kilometers km about 300 miles in length, although some estuary fish travel 1,000 km 600 miles or more up the river Novomodny et al. 2004, p. 18 and may spend up to 2 years there prior to reproducing Krykhtin and Svirskii 1997, p. 237.
Spawning occurs following migration, between May and September. Known spawning sites are primarily in the middle Amur River, including several major grounds in Luobei, Xunke, and Tongjiang counties Wei et al. 1997, p.
245. This evidence is consistent with findings that the population of Amur sturgeon was historically greatest in this stretch of the river Krykhtin and Svirskii 1997, p. 237.

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Females can lay upwards of 1.3
million eggs in a single spawning, although the norm is between 190,000
and 300,000 eggs Koshelev et al. 2014b, p. 1127; Zhang 1985 cited in Zhuang et al. 2002, pp. 660661. In related sturgeon, only about 1 in 2,000 survive their first year post-hatching Jaric and Gessner 2013, table 1; Jager et al. 2002, table 1. Thereafter, 20 to 90 percent of juvenile fish survive annually Jaric and Gessner 2013, table 1; Jager et al. 2002, table 1. Although age-specific survival data for Amur sturgeon in particular are not available, the species very likely has similar patterns of survival by age Kappenmann 2020, pers. comm..
Larvae hatch faster in warmer compared to colder water, emerging in 3 to 14 days Krykhtin and Svirskii 1997, p. 237, then likely drift downstream. They begin feeding around 9 days post-hatching Zhuang et al.
2003, figure 5; Krykhtin and Svirskii 1997, p. 237. After about 30 days, they metamorphose into juvenile fish of about 4 centimeters cm 2 inches in length and 3 grams 0.1 ounces in weight Zhuang et al. 1999a and Liu et al. 2000 cited in Zhuang et al. 2002, p.
661. Juveniles feed in shallow shorelines and smaller tributaries and lakes Zhuang et al. 2002, p. 659.
By 1 year of age, fish average approximately 30 cm 12 inches;
Nikolskii 1960 cited in Zhuang et al.
2002, p. 660. Six-year-old individuals may be 90 cm 35 inches, 25-year-old fish 2 m 7 feet, and large 40-year-old fish can approach 2.5 m 8 feet; Zhang 1985 cited in Zhuang et al. 2002, p.
660.
Amur sturgeon prey on larval insects, small mollusks, crustaceans, and fish Novomody et al. 2004, p. 19; Nikolskii 1960 and Sun et al. 2000 cited in Zhuang et al. 2002, p. 660, with geographic and age-based variation in preferred food items Kolybov and Koshelev 2014, p. 489; Sun et al. 2000
and Nikolskii 1960 cited in Zhuang et al. 2000, p. 660; Krykhtin and Svirskii 1997, p. 236.
Population Biology Amur sturgeon are thought to spawn primarily within the same larger river regions as those in which they feed throughout the year Ruban and Qiwei 2010, not paginated; Novomodny et al.
2004, p. 18. Therefore, we followed the limited literature e.g., Koshelev et al.
2014a, entire; Krykhtin and Svirskii 1997, pp. 236238 and considered fish in four river regions to be the analysis units for our assessment of the species status. These units are:

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