K. R. Bestgen, K. A. Zelasko, and G. C. White. Monitoring ...

larvae (9–13 mm TL) suggested relatively late spawning in a location where razorback sucker
was not common in recent years (KRB, unpublished data).
In the middle Green River, a set of sites that are regularly available for sampling even
when flows are extremely high or low are sampled each year. These include Cliff Creek, Stewart
Lake Outlet, Old Charley Wash inlet or outlet, and Greasewood Corral. Those sites reliably
provide first-capture-of-the-year information across the longitudinal extent of the middle Green
River, especially at Cliff Creek, which is just downstream of known spawning areas (Hedrick et
al. 2009; 2010; Bestgen et al. 2011). That site is especially important given the emphasis on
using real-time information to dictate timing of annual releases from Flaming Gorge Dam, which
are used to provide access of larvae to floodplain wetlands. Several other sites are added
annually based on availability of habitat including Baeser Wash, Walker Hollow, and other sites
near or in Ouray National Wildlife Refuge. Those sites provide additional information on
spawning success of adult razorback suckers and may also indicate presence and abundance of
larvae in the vicinity of floodplain wetland breaches. That information may be critical to
understanding efficacy of various wetland types to entrain razorback sucker larvae to enhance
recruitment, information which is in turn important in experiments to understand timing and
duration of flow events needed to effect recruitment of razorback suckers in floodplain wetlands
in the middle Green River. Sampling in or near entrances to floodplain wetlands is a key
component of the Larval Trigger Study Plan (LaGory et al. 2012), which describes a sampling
program and approach to evaluate efficacy of using first appearance of sucker larvae to initiate
higher flow releases in spring-time from Flaming Gorge Dam.
We recommend continuation of the existing program of light trap sampling for early life
history stage of razorback sucker in the middle Green River. Especially important is early
monitoring of upstream sites at Cliff Creek and Stewart Lake to ascertain presence of native
sucker larvae in the middle Green River to trigger spring flow releases from Flaming Gorge Dam
in spring. We are confident that those sites and others will provide that information accurately.
We base those assertions on recaptures of marked razorback sucker larvae released in the Green
River in differing batch sizes and under different flow regimes (Hedrick et al. 2009; 2010;
Bestgen et al. 2011). Even with relatively small batches of larvae (2004), or under relatively
high flows (2005), sampling with light traps at various sentinel stations detected marked larvae
within 18 to 48 hours of release, and as much as 90 km downstream from release sites.
Nevertheless, because of the importance of detection of reproduction by native suckers with light
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