Inefficacy of light-traps in the upper Ohio River

We studied larval and young-of-year fish distribution in the Ohio River within Pennsylvania for a baseline study sponsored by the U.S. Army Corps of Engineers.  Fish were collected from the uppermost four pools of the Ohio River using trawls, meter nets, dip-nets, seines with 800µm mesh, and light-traps (usually used in lentic habitats).  At the Corps’ suggestion, we attempted to use light-traps in shallow near-shore habitats at five of 29 sampling stations from April to October 2009.  Typically, sets of 10 light-traps were fished overnight, with four seine hauls conducted adjacently after we removed fishes from light-traps.  We captured 165 individuals representing 16 species using light-traps and we seined 3,067 individuals distributed among 25 species, at the same stations during the same time period.  Light-traps were ineffective because of flushing action due to river flow and wakes created by barge traffic.  Wakes also washed many light-traps ashore, swept some away, or destroyed them against structures in the river.  Light-traps are not efficient at collecting negatively phototactic species and where there is limited light distribution.  Despite the problems experienced here, light-traps may prove somewhat useful in backwater riverine habitats or in similar lotic habitats where other methods are impossible.