Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Endangered Suckers: Sucker Description, Life History, Habitat, Distribution, and
Abundance
immediately downstream of the US Highway 97 bridge, and in the Beatty Gap
area of the upper Sprague River (Buettner and Scoppettone 1990, Tyler et al.
2007, Ellsworth et al. 2007). Other areas in the Sprague River watershed where
Lost River sucker spawning is suspected include the lower Sycan River and the
Sprague River near Kamkaun Spring (Ellsworth et al. 2007).
Presently, shortnose suckers from UKL spawn in the lower Williamson and
Sprague rivers (Buettner and Scoppettone 1990), principally below Chiloquin
Dam (Tyler et al. 2007, Ellsworth et al. 2007). The few adult shortnose suckers
captured at the shoreline spawning areas in UKL indicate that some shortnose
sucker spawning is likely to still occur at the shoreline spawning areas (Hayes et
al. 2002, 2004, Barry et al. 2007 UKL). Although species identification is not
apparent, sucker spawning is also suspected in the Wood River. Whereas it is
possible that sucker spawning may occur in other small tributaries to UKL and its
main tributaries, fisheries investigations have not identified sucker populations in
tributaries other than the Williamson, Sprague, and Wood rivers.
Since listing, information on relative abundance of adult sucker populations has
been obtained from the number of captured suckers migrating up the Williamson
River each spring to spawn (USFWS 2002). The Williamson River spawning
abundance index, based on actual and interpolated catch per unit effort (CPUE)
data, shows a decline in abundance for both species during the three fish die-offs
in the mid-1990s and a hiatus in recruitment of new individuals from 1998 to
1999 before the population began to increase in 2000 (Figure 2-3; Cunningham et
al. 2002, Tyler et al. 2004). The increase in the spawning abundance index that
began in 2000 could represent the recruitment of a single dominant year class
over a period of two years or the recruitment of two distinct year classes. If a
single year class recruited in over two years during 2000 and 2001 it would likely
be the 1991 year class for Lost River suckers and the 1993 year class for
shortnose suckers (USFWS 2002).
Since 2001, data from adult population monitoring in UKL has become robust
enough to perform a capture-recapture analysis for shoreline spawning Lost River
suckers that estimates the annual survivorship (Janney and Shively 2007, Janney
et al. 2007). Furthermore, population assessment for UKL suckers can be
understood by considering length frequency histograms and population change
estimates as provided in Janney and Shively (2007) and Janney et al. (2007).
Length Frequency
Recent analysis of sucker population data corroborates the assessment in
Scoppottone and Vinyard (1991) at the time of listing that the population of Lost
River suckers in UKL was dominated by older individuals and showed no
evidence of substantial recruitment during the 1980s and early 1990s (Janney and
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