Razorback Sucker- EP - Revision history

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Razorback Sucker
The razorback sucker [RBS; Xyrauchen texanus (Abbott, 1860)] was listed as a federally endangered species in 1991. It is a large, mainstream catastomid species that ranged widely through the Colorado River basin in pre-dam time. This species grows to more than 2 ft in length and may live more than 40 yr. Adult RBS bear a pronounced dorsal keel. Like humpback chub, the sucker’s dorsal keel has been believed to stabilize navigation in swift, turbulent waters, but experimental studies fail to show such a benefit and suggest the elevated dorsal keel reduced the likelihood of predation by Colorado pikeminnow (Ptychocheilus lucius Girard 1856; Portz and Tyus 2004). RBS feed on biofilm, detritus, and associated aquatic invertebrates on firm benthic surfaces. RBS life history studies in the upper Colorado River Basin revealed that spawning occurs in April and May over sand and gravel substrates in waters ranging from 50-64° F (10-18oC). Males establish breeding territories in shallow water and defend their breeding areas with downward eye rolls, which flash UV light. Females are attended by 2-12 males and deposit 24,500-76,600 eggs/yr, which adhere to pea gravels. Eggs will not hatch in water less than 50°F, (10°C). Radio-tagging studies show that RBS prefer flat-water reaches of rivers (Tyus 1987). RBS in the Colorado River were larger than those in the Yampa/Green drainage, presumably because of warmer water temperatures in the mainstream Colorado River (Joseph et al. 1977).
RBS were reported from the lower Paria River in pre-dam time, but the last RBS known from central Grand Canyon was captured in the early 1980’s near the Little Colorado River confluence. Population declines have been attributed to reproduction failure due to impoundment-related water temperature changes and predation by non-native fish species. Even though RBS is easily propagated, and is consistently nominated as the top candidate for recovery, more than 25 yr of symposia and discussion about that topic have failed to result in its reintroduction into Grand Canyon. Old, large individuals still exist in Lakes Mohave and Mead, and 2012 fish electrofishing monitoring in lowermost Grand Canyon revealed a few RBS below Mile 240 in Grand Canyon; however, natural reproduction remains low to non-existent.

Kanab Ambersnail
Federally endangered since 1991, the Kanab ambersnail [KAS; Oxyloma haydeni haydeni (kanabensis; Pilsbry 1948)] is a half inch-long, dextral (up-to-the-right-spiraling) landsnail with a high, delicate spire, and which only exists in three spring-fed wetlands in southern Utah and northern Arizona. Discovered in Grand Canyon during tributary monitoring at Vaseys Paradise in 1990, this hermaphroditic species has an annual life cycle. Eggs are laid in August, larval snails grow until mid-October, then overwinter by sealing themselves with mucous to stone, wood, or (often unfortunately) dead leaves, which may blow away. Those snails that survive the vicissitudes of winter emerge in March or April, complete their growth by mid-summer and breed. Those with female function lay several clutches of about 40 eggs in gelatinous masses on the undersides of moist stems and leaves. KAS feeds on biofilm on moist, dead stems of cardinal monkeyflower and other wetland plants, but they seem to prefer feeding on the tender new leaves of non-native watercress. About 10% of adult KAS at Vaseys Paradise are infected with a parasitic Leucochloridium flatworm, which evacuates from the snail in August and completes its life cycle in songbirds. Although common in Utah, only two other natural populations of Oxyloma ambersnails occur in Arizona, one at Leopard Frog Marsh at Mile -9L and the other at Indian Gardens on the Bright Angel Trail in central Grand Canyon.
After scouring springtime floods were eliminated by Glen Canyon Dam in 1963, Vaseys Paradise vegetation cover expanded by about 40% to nearly an acre. The post-dam KAS population there is now likely substantially greater than it was in predam time. The endangered status of KAS has resulted in several Biological Opinions from the U.S. Fish and Wildlife Service regarding the impacts of planned high flow experiments. Actions to protect the Vaseys snail population have included: developing secondary, off-river KAS populations in tributaries; transporting all KAS in the mainstream flood zone to higher elevations; moving and protecting vegetation patches that support KAS; and monitoring flood impacts and among-year population variation. Detailed morphological and genetics analyses by the U.S. Geological Survey will soon propose synonomy of Kanab ambersnail into the more widespread and common North American Niobrara ambersnail taxon (Oxyloma h. haydeni Pilsbry 1948), thus Kanab ambersnails will soon no longer exist as a taxonomic entity.

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 ''CRE AT-RISK SPECIES VIGNETTES – Larry Stevens''
 *'''Razorback Sucker'''
-	*The razorback sucker [RBS; Xyrauchen texanus (Abbott, 1860)] was listed as a federally endangered species in 1991. It is a large, mainstream catastomid species that ranged widely through the Colorado River basin in pre-dam time. This species grows to more than 2 ft in length and may live more than 40 yr. Adult RBS bear a pronounced dorsal keel. Like humpback chub, the sucker’s dorsal keel has been believed to stabilize navigation in swift, turbulent waters, but experimental studies fail to show such a benefit and suggest the elevated dorsal keel reduced the likelihood of predation by Colorado pikeminnow (Ptychocheilus lucius Girard 1856; Portz and Tyus 2004). RBS feed on biofilm, detritus, and associated aquatic invertebrates on firm benthic surfaces.  RBS life history studies in the upper Colorado River Basin revealed that spawning occurs in April and May over sand and gravel substrates in waters ranging from 50-64° F (10-18oC). Males establish breeding territories in shallow water and defend their breeding areas with downward eye rolls, which flash UV light. Females are attended by 2-12 males and deposit 24,500-76,600 eggs/yr, which adhere to pea gravels. Eggs will not hatch in water less than 50°F, (10°C). Radio-tagging studies show that RBS prefer flat-water reaches of rivers (Tyus 1987). RBS in the Colorado River were larger than those in the Yampa/Green drainage, presumably because of warmer water temperatures in the mainstream Colorado River (Joseph et al. 1977).
+*The razorback sucker [RBS; Xyrauchen texanus (Abbott, 1860)] was listed as a federally endangered species in 1991.
-	*RBS were reported from the lower Paria River in pre-dam time, but the last RBS known from central Grand Canyon was captured in the early 1980’s near the Little Colorado River confluence. Population declines have been attributed to reproduction failure due to impoundment-related water temperature changes and predation by non-native fish species. Even though RBS is easily propagated, and is consistently nominated as the top candidate for recovery, more than 25 yr of symposia and discussion about that topic have failed to result in its reintroduction into Grand Canyon. Old, large individuals still exist in Lakes Mohave and Mead, and 2012 fish electrofishing monitoring in lowermost Grand Canyon revealed a few RBS below Mile 240 in Grand Canyon; however, natural reproduction remains low to non-existent.
+*It is a large, mainstream catastomid species that ranged widely through the Colorado River basin in pre-dam time.