Spatial analysis of pallid sturgeon Scaphirhynchus albus distribution in the Missouri River, South Dakota

P>Movement and distribution of the endangered pallid sturgeon Scaphirhynchus albus has generally been documented using radio telemetry. However, because of the time and cost involved in tracking individual fish (i.e. small sample size), it is often difficult to evaluate spatial distribution of groups of fish over long time periods (> 3 years). Standardized sampling for pallid sturgeon, which relies on a variety of gear types, has been conducted on the Missouri River downstream of Fort Randall Dam annually since 2003. Using catch data from 2003 to 2006, the spatial distribution of juvenile pallid sturgeon was evaluated using spatial scan statistics. Presence/absence of pallid sturgeon was summarized from a variety of gear and distribution patterns were analyzed based on: (i) each gear per season, (ii) all gear pooled per season, (iii) each gear pooled across seasons, and (iv) pooled data from all gear and years combined. Three significant clusters of pallid sturgeon captures were identified when all gear and years were pooled. Distribution patterns identified using data from summer trammel nets agreed well with the overall pooled dataset and could be used to identify areas with a high probability of pallid sturgeon presence. This methodology can be used to identify areas where pallid sturgeon are likely to occur, thus improving sampling efficiency for monitoring vital statistics for this endangered species. Moreover, this approach could be applied to other reaches of the Missouri River using existing data from the Pallid Sturgeon Monitoring and Assessment Program. Once identified, these areas could then be evaluated to better understand the habitat requirements of pallid sturgeon.