The Mini-Missouri Trawl: A Useful Methodology for Sampling Small-Bodied Fishes in Small and Large River Systems

摘要

Sampling has been conducted in small to large rivers of the Midwest and northeastern United States to determine the usfulness of a modified Missouri trawl designed to increase species detection of small-bodied fish species. We modified the Missouri trawl, which is a 4.8 m standard two-seam slingshot balloon trawl with a small mesh cover, by reducing the size (to a 2.44 m) and cover. The modified Missouri trawl (a.k.a. the mini-Missouri trawl) increased the number of small-bodied aquatic species of concern captured over that of previously used gears. For instance, shoal chub (Macrhybopsis hyostoma) had only been captured in the St. Croix River of Minnesota at three locations since 1960, yet we sampled it at 14 new locations in September, 2004 employing this methodology. Because of our success in these diverse and numerous systems, we believe this is a useful methodology for sampling the benthic fish community in many aquatic systems when other sampling methods are difficult to use because of water depths and/or velocities.