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Federal Register / Vol. 86, No. 1 / Monday, January 4, 2021 / Rules and Regulations withstand catastrophic events for which adaptation is unlikely. It is associated with the number, distribution, and resilience of individual populations throughout the current range of the species. Representation is the ability of a species to adapt to novel changes in its environment, as measured by its ecological and genetic diversity and its ability to disperse and colonize new areas.
Taxonomy and Description The June sucker, a unique lake sucker named for the month in which it spawns, was first collected and described by David S. Jordan in 1878, in Utah Lake, Utah County, Utah Jordan 1878, entire. However, taxonomic questions regarding hybridization of the June sucker and co-occurring Utah sucker Catostomus ardens ultimately resulted in reclassification of the species as described below.
The two species likely evolved together in Utah Lake. During the 1930s, a severe drought stressed the sucker populations in Utah Lake, increasing the incidence of June and Utah sucker hybridization Miller and Smith 1981, p.
7. After this hybridization event, as sucker populations increased in abundance, the new genes that occurred in both the June sucker and Utah sucker populations resulted in hybrid characteristics within both populations Evans 1997, p. 8. It is likely that the two species may have hybridized at multiple points in the past, in response to environmental bottlenecks Evans 1997, pp. 912. As a result of the hybridization event in the 1930s, two subspecies of June sucker were originally identifiedChasmistes liorus liorus for sucker specimens collected in Utah Lake in the late 1800s, and Chasmistes liorus mictus for specimens collected after 1939, following the drought years Miller and Smith 1981, p. 11. This classification was never corroborated, and because the June sucker maintained its distinctiveness from other lake suckers despite hybridization, we determined that it should be listed as a distinct species under the name Chasmistes liorus 51
FR 10851; March 31, 1986.
The June sucker has a large, robust body; a wide, rounded head; and a hump on the snout Scoppettone and Vinyard 1991, p. 1. Adults are 1724
inches in 43.261.0 centimeters cm in length Scoppettone and Vinyard 1991, p. 1; Belk 1998, p. 2. Lake suckers are mid-water planktivores plankton feeders. The June sucker is a long-lived species, living to 40 years or more Scoppettone and Vinyard 1991, p. 3;
Belk 1998, p. 6. In the wild, June
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suckers reach reproductive maturity at 510 years of age. They exhibit rapid growth for the first 35 years, with intermediate growth rates between ages 810, and a further reduced growth rate after age 10. Growth between sexes does not differ within the first 10 years Scoppettone and Vinyard 1991, p. 9.
Distribution and Habitat The June sucker is native and endemic to Utah Lake and its tributaries, which are the primary spawning habitat for the species. The June sucker is not found outside of its native range except in two populations established for conservation purposes. A
refuge population was created as part of the JSRIP stocking program to enhance and secure the species population in Utah Lake at the Fisheries Experiment Station FES hatchery in Logan, Utah Service 2015, entire. An additional population was established in Red Butte Reservoir, Salt Lake County, Utah, in 2004 and is now self-sustaining Utah Division of Wildlife Resources UDWR
2010, pp. 45. These additional populations have aided in retaining ecologic and genetic diversity in June sucker, which in turn aids the species in adapting to changing environmental conditions i.e., increases representation JSRIP 2018, pp. 23.
Utah Lake is a remnant of ancient Lake Bonneville, and is one of the largest natural freshwater lakes in the western United States. It covers an area of approximately 150 square miles mi2
400 square kilometers km2 and is relatively shallow, averaging 9 feet ft 2.7 meters m in depth Brimhall and Merritt 1981, pp. 23. The lake lies west of Provo, Utah, and is the terminus for several rivers and creeks, including the Provo, Spanish Fork, and American Fork Rivers, and Hobble and Battle Creeks. The outflow of Utah Lake is the Jordan River, which flows north into the Great Salt Lake, a terminal basin.
Utah Lake is located in a sedimentary drainage basin dominated by erosive soils with high salt concentrations. Utah Lake had a sediment filling rate of about 0.03 in 1 millimeter mm per year over the past 10,000 years; this rate more than doubled with the urbanization of Utah Valley Brimhall and Merritt 1981, pp. 35. Faults under the lake appear to be lowering the lake bed at about the same rate as sediment is filling it Brimhall and Merritt 1981, pp. 1011. Inputs of nutrient-rich sediments combined with the lakes high evaporation rate cause high levels of sediment loading, high soluble salt concentrations, and high nutrient levels as a baseline condition Brimhall and Merritt 1981, p. 11.

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Shallow lakes, such as Utah Lake, are typically characterized as having one of two ecological states: A clear water state or a turbid water state Scheffer 1998, p.
10. The clear water state is often dominated by rooted aquatic macrophytes aquatic plants that can greatly reduce turbidity by securing bottom sediments Carpenter and Lodge 1986, p. 4; Madsen et al. 2001, p. 6 and preventing excessive phytoplankton algae production through a suite of mechanisms Timms and Moss 1984, pp. 35. Alternatively, a shallow lake in a turbid water state contains little or no aquatic vegetation to secure bottom sediments Madsen et al. 2001, p. 9. As a result, fish movement and wave action can easily suspend lake-bottom sediments Madsen et al. 2001, p. 9. In addition, fish can promote algal production by recycling nutrients both through feeding activity and excretion.
Fish can also suppress zooplankton densities through predation, and the zooplankton would otherwise suppress algal abundance Timms and Moss 1984, p. 11; Brett and Goldman 1996, p.
3.
Historically, Utah Lake existed in a clear water state dominated by rooted aquatic vegetation, as shown in sediment cores extracted from Utah Lake Macharia and Power 2011, p. 3.
Sediment cores reveal a shift in the state of the lake shortly after European settlement of Utah Valley to an algaedominated, turbid condition, lacking macrophytic vegetation that serves as refugial habitat for June sucker Brimhill and Merritt 1981, p. 16; Scheffer 1998, p. 6; Hickman and Thurin 2007, p. 8;
Macharia and Power 2011, p. 5. This shift is believed to be a result of excessive nutrient input, managementinduced fluctuations in lake levels, and the introduction of common carp Cyprinus carpio. The result of compounded natural and human-caused effects is a present-day lake ecosystem that is dominated by algae, rather than the clear water state in which June sucker evolved.
The extent of ideal riverine habitat available for spawning adults and developing larval June sucker was more abundant historically than it is currently. Prior to settlement of Utah Valley, spawning tributaries, such as the Provo, Spanish Fork, and American Fork Rivers, and Hobble Creek, contained large deltas with braided, slow, meandering channels and aquatic vegetation that provided suitable spawning and larval rearing habitat Olsen et al. 2002, p. 4. Multiple spawning tributaries provided redundancy for June sucker. The range of diverse habitats historically present
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