Scaphirhynchus Conference: Alabama, Pallid, and Shovelnose Sturgeon

St. Louis, Missouri, 11-13 January 2005

43.  TRAMMEL NET EFFICIENCY FOR JUVENILE PALLID STURGEON (SCAPHIRHYNCHUS ALBUS) AND SHOVELNOSE STURGEON (SCAPHIRHYNCHUS PLATORYNCHUS): IMPLICATIONS FOR SAMPLING DESIGN.

Eric W. Oldenburg, Paul C. Gerrity, and Christopher S. Guy, Montana Cooperative Fishery Research Unit, 301 Lewis Hall, Department of Ecology, Montana State University, Bozeman, MT  59717; Phone 406-994-3491; FAX 406-994-7479; actinopterygii@hotmail.com

William M. Gardner, Montana Department of Fish, Wildlife, and Parks, P.O. Box 938, 2358 Airport Road, Lewistown, MT  59457; Phone 406-538-4658; bgardner@state.mt.us

To accurately document continued decline or recovery of sturgeon (Scaphirhynchus spp.), the efficiency of sampling these species needs to be evaluated.  Drifted trammel nets are considered an important tool for sampling sturgeon in lotic systems.  However, little information exists on the efficiency of this sampling gear.  Thus, our objective was to evaluate the efficiency of drifting trammel nets for sampling juvenile pallid sturgeon (Scaphirhynchus albus) and shovelnose sturgeon (Scaphirhynchus platorynchus).  During the summers of 2003 and 2004, we attempted to recapture radio-tagged juvenile pallid sturgeon and shovelnose sturgeon at 43 locations in the Missouri River above Fort Peck Reservoir, Montana.  After a radio-tagged fish was located, a trammel net was deployed 75-m upstream and retrieved 45-m downstream of the fish location.  A maximum of four drifts were attempted at each location.  Drifting trammel net efficiency was 53.5% by location, 29.5% by drift, and first drift efficiency was 37.2%. Sixty-nine percent of the sturgeon were captured on the first drift and subsequent drifts were often unsuccessful.  Stepwise logistic regression was used to model the probability that a drift would not capture a sturgeon.  However, none of the abiotic variables we measured were useful in the model.  These results suggest that drifted trammel nets are a moderately effective sampling gear for juvenile sturgeon in lotic systems.  When considering sampling design, our results suggest that it is most efficient to conduct all trammel net drifts at different locations, rather than sampling the same location more than once.