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

Yet another aspect of sampling and analysis could be formal occupancy analysis of
sampling data. This involves multiple samples collected from the same location (could be in
concert with releases described above) and at several locations. The advantage is occupancy
estimation analysis allows for estimation of probability of occurrence (here, larvae) in the face of
imperfect detection information (i.e., the idea that larvae may not be detected even when present,
with inherent methods to correct for that; see Falke et al. [2010] for more information) and is
especially useful if number of larvae increases over time. This would be especially useful for
Larval Trigger study assessments, which will rely on knowledge of occupancy of larvae in
wetlands in late spring-early summer to guide sampling later in summer or autumn.
Taxonomic verification of larvae.—Identification of larvae with traditional
morphological and pigment characteristics works well for most specimens captured in light traps
(Snyder and Muth 2004). This is true because razorback sucker larvae hatch early and at a
smaller size than other native suckers and have earlier (at a smaller size) development of key
structures through the early life history stage. Compared to the commonest non-native, the white
sucker Catostomus commersonii, larvae of razorback sucker have key morphological
development event differences (gut coiling), transitions to various larval life stages (e.g., flexion
to post-flexion mesolarvae) occurs at a smaller size, and pigmentation patterns are quite different
than the aforementioned species. However, with the increase in abundance of non-native
catostmids (e.g., white sucker) and increased hybridization rates among various native and nonnative
catostomids in some portions of the basin, verification of specimens determined to be of
questionable taxonomic identity could be very useful. A previous study using allozymes
documented that traditional techniques are very accurate to identify razorback suckers (pers.
comm., D. Probstel, formerly of Colorado State University) since nearly all razorback suckers
and those identified as questionable were in fact bona fide razorback suckers. More recently and
using other techniques, a few fish identified as razorback suckers or razorback suckers where
identity was slightly questionable (“razorback sucker?”) were identified using genetic techniques
as some other taxa (J. Wood, Pisces Molecular, Boulder, Colorado); sample size for study
specimens and reference fish species was low, reference fish identity may have been
questionable, and the number of molecular markers resolved was small so the results are still
under review. Regardless, reliable genetic techniques based on samples of known razorback
sucker specimens and those of other reference species to benchmark results, would verify
efficacy of traditional taxonomy, determine whether traditional techniques are useful to identify
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