2022-12-19_GENERAL DOCUMENTS - C1981010

• Permit No: C1981010
• IBM Index Class Name: General Documents
• Doc Date: 12/19/2022
• Doc Name Note: Section 7 Consultation.
• Doc Name: Correspondence
• From: Clayton Creed
• To: DRMS
• Email Name: RAR
• Email Name: JLE
• Media Type: D
• Archive: No

Desalation-Gray Canyon Black Rocks
rnnn 16W
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1 JCM] -
4000
low
3000 8W
2000 f,On - T
4 Ill
1000 W -
200
n n
2000 2002 2004 2006 2008 2010 2012 2014 2016 1996 1998 2000 20D2 2004 2006 2008 2010 2012 2D14
Cataract Canyon Westwater
1800 14000
1600
131M70
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E 1WU0
V, 1200
1000 8WD
c
m
c 800 MM
600 4Wn
Q 400
2W00
200
6
2002 2003 2004 2005 2006 IJ96 1J98 2900 2W2 2004 2006 2UD9 2010 2012 2014
Figure 8. Adult humpback chub population estimates with confidence intervals for four
populations in the upper Colorado River Basin(note that the scale differs among the graphs for
the different populations). Clockwise from upper left: Desolation-Gray Canyons(from Badame
2011,2012; Service 2015a);Black Rocks(from Francis and McAda 2011);Westwater Canyon
(from Elverud 2011); and Cataract Canyon(from Badame 2008).
On the Colorado River of the upper Colorado River basin,three humpback chub populations are
recognized. Black Rocks and Westwater Canyon have enough exchange of individuals that they
are considered a single core population. In Black Rocks, estimates of wild adults have varied
from about 800 in 1998, 900 in 1999, and 500 in 2000 and 2003 (Figure 8) (McAda 2007). The
most recent estimates, in 2007-2008 were 345 and 287,respectively. During the fall of 2011
and 2012, 78 and 112 individual adult humpback chub were caught respectively - similar to the
numbers caught in 2007 and 2008 (61 and 74,respectively). Population estimates for Black
Rocks for 2011 and 2012 were 379 and 403,respectively. Researchers caution that 78
largemouth bass and the same number of gizzard shad were collected in Black Rocks in 2012.
This represents a ten-fold increase over the 2011 catch. The Westwater Canyon estimates of
wild adults range from about 4,700 in 1998 to 2,500 in 1999, 2000, and 2003 (Jackson and
Hudson 2005). The 2007-2008 estimates were about 1,750 and 1,300. The large declines in
humpback chub densities in both Black Rocks and Westwater Canyons occurred in the late
1990's and are not attributed to more recent increases of nonnative predators in the Colorado
River.
In 2008,the core population (Black Rocks /Westwater combined) dropped below the population
size downlist criterion (MVP= 2,100 adults) for the first time. In 2011,we saw some recovery
in those populations where the estimate for adults in Westwater Canyon alone was 1,467;
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