A Comparison of Fish Catch Rate with Two Different Benthic Trawls in the Missouri River

ABSTRACT

Trawling is commonly used to assess abundance, distribution, and diversity of fish assemblages as well as to commercially harvest various species of fish. We compared fish community structure and total catch of a 4.9-m otter trawl (OT16; 19-mm bar mesh body with a 6-mm mesh cod end) with a smaller mesh trawl of similar physical dimensions (OT01; composed entirely of 4-mm bar mesh). Total catch from both trawls revealed a trend toward the capture of smaller-sized individuals in the OTO1 and larger individuals in the OT16; however, both trawls provided a high degree of overlap in species richness and diversity. Shannon's index values (H′) were 2.47 and 2.40 for the OT16 and the OT01, respectively, signifying that both of these trawls caught a diverse assortment of fishes, regardless of mesh size. An analysis of similarity test resulted in strong similarities in fish assemblage composition between both trawls, corroborating diversity indices. Our results indicate that 19-mm and 4-mm bar mesh are both effective mesh sizes to collect a variety of benthic fish species of various size classes in the Missouri River.