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

• Determining origin of untagged fish, whether hatchery-reared or wild, would aid in
determining recruitment rates of razorback suckers.
• Simulations are useful to guide assignment of minimal levels of sampling effort to
accomplish goals of parameter estimation.
• Rigorous data analysis is needed to evaluate whether sampling efforts for larger juvenile
and adult razorback sucker are effective at improving accuracy and reliability of
abundance and survival estimates in the future.
RECOMMENDATIONS
• Maintain present sampling to monitor timing of presence and abundance of razorback
sucker larvae and juveniles in the middle and lower Green and Colorado rivers.
Minimally, high quality and close-up digital photographs should be taken of questionable
specimens that include the lateral view of the body as well as the ventral view of the
mouth, and in some cases, specimen preservation in appropriate solutions should be
considered.
• Maintain sampling for larvae in the lower White River where reproduction was
documented for the first time in 2011 at levels outlined in project 22f. Sampling should
be evaluated in the future (after 3 more years) and adapted to presence and abundance
patterns noted.
• Conduct additional but relatively limited fine-mesh seine sampling in the lower Yampa
River for razorback sucker larvae within 1–2 weeks after first appearance of middle
Green River larvae.
• Maintain sampling for razorback sucker larvae in the Colorado River in accordance with
plans to evaluate razorback sucker reproduction in the lower Gunnison and Colorado
rivers per project 163, perhaps adding light trap sampling in gravel pit ponds and other
appropriate areas. When higher levels of reproduction there are noted, revise the
monitoring program to incorporate new information on distribution of larvae relative to
spawning areas and establishment of sentinel sites that can be used to monitor timing of
reproduction and population abundance over time.
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