PNNL

Abstract

Pallid sturgeon Scaphirhynchus albus and shovelnose sturgeon Scaphirhynchus platorynchus are commonly sampled using drifting-trammel nets in the Missouri River basin. Despite that drifting trammel nets have been used for decades to sample these species, little is known about the capture efficiency of this gear. We estimated conditional capture probability and gear efficiency for drifting trammel nets. In addition we examined several abiotic variables that were assumed to influence the success of capturing a pallid sturgeon or shovelnose sturgeon in a drifting trammel net. Conditional capture probability varied from 0.36 on the first attempt to 0.50 on the second attempt. Drifting trammel nets are relatively efficient and we suggest that they continue to be used to sample in large turbid rivers. The high variability associated with sampling pallid sturgeon and shovelnose sturgeon using drifting trammel nets is likely related to low abundance and patchy distributions. Thus, we suggest using more appropriate sampling designs for rare species.