Evaluation of a Substrate-Disturbing Brail Added to the Mini-Missouri Trawl for Capture of Madtoms, Sculpins, and Darters

ABSTRACT

Some species of benthic fishes are rare, threatened or endangered and the tools that are used to sample them are not well developed. We added a substrate-disturbing brail to a small benthic trawl to improve catches of crevice-seeking and burrowing fishes in three rivers with differing substrates. The brail trawl was constructed from a mini-Missouri trawl by reducing the floatline length to 1.22 m and adding a 1.22-m mussel brail to the trawl rope 0.2 m forward of the otter doors. This brail disturbed the substrate aggressively just ahead of the trawl and sent benthic fishes such as darters (Etheostoma, Percina, Ammocrypta spp.), sculpins (Cottus spp.) and madtoms (Noturus) into the water column to be captured. Sampling was done on the Black River, St. Francis River and Mississippi River to compare the brail trawl to a mini-Missouri trawl with the same floatline length and a foam core poly rope in place of the brail. Thirty-four hauls per gear per river were done to evaluate the effectiveness of the brail for capturing benthic fishes. We used a paired sample Wilcoxon signed-ranks test with continuity correction to compare individual species and groups of species on each river. The brail trawl was more effective at capturing Noturus spp., Cottus carolinae, and non-burrowing darters. However, the brail did not increase the capture of burrowing darters.