IS SHALLOW WATER A SUITABLE SURROGATE FOR ASSESSING EFFORTS TO ADDRESS PALLID STURGEON POPULATION DECLINES?

It is hypothesized that slow, shallow water habitats benefit larval pallid sturgeon Scaphirhynchus albus; however, testing this hypothesis is difficult, given the low number of larval pallid sturgeon present in large rivers. In contrast, relatively large numbers of age-0 shovelnose sturgeon Scaphirhynchus platorynchus have been sampled, providing a potentially useful baseline to assess the importance of slow, shallow water to age-0 sturgeon of both species (hereafter age-0 sturgeon) in the lower Missouri River. Thus, we investigated the potential relationships between the prevalence of shallow water \u3c1.5m and the age-0 sturgeon catch rates at multiple scales. Age-0 sturgeon were usually sampled in water \u3e1.5 m, and catch rates were usually highest in the upper half [i.e. river kilometer (RKM) 400 to 800] of the lower Missouri River study area, whereas the availability of water \u3c1.5m was usually highest in the lower half (i.e. RKM 0 to 400). Similarly, there was no relationship between age-0 sturgeon mean catch-per-unit effort and ha/km of water \u3c1.5m at any studied scale. Our results may suggest that shallow water, as currently defined, may not be a suitable surrogate for assessing efforts to address pallid sturgeon population declines. However, it is still unknown if lack of appropriate habitat is currently limiting pallid sturgeon