Monday, June 4, 2007 - 3:15 PM
49

Benthic Trawling as a Supplement to Electrofishing on the Ohio River

Jeff A. Thomas, ORSANCO, 5735 Kellogg Ave, Cincinnati, OH 45228

ORSANCO has been monitoring fish populations of the Ohio River since 1957 through both lockchamber sampling using rotenone and boat-mounted electrofishing.  While we have considered electrofishing to be the best single method for assessing fish communities of the river, the deployment of a second method has also been considered in order to sample aspects of the community not captured by electrofishing.  In 2006, benthic trawling was conducted at 60 electrofishing zones to determine the utility of this method as a secondary collection technique to better characterize fish populations of the Ohio River.  Four, one minute trawls were conducted at each 500 meter electrofishing transect at different depths and/or at different segments of the transect.  An 8’ wide trawl was used for all sampling.  Overall, 240 trawls were conducted, of which fish were collected in 72% (172).  While average time spent at each 500 meter transect trawling was comparable to time spent electrofishing (~45 min), electrofishing returned many more individuals (9157 to 2323) and species (62 to 22). Trawling did, however, regularly capture species either not observed at all, or not observed in high numbers, in the electrofishing data.  Therefore, trawling will be conducted again in 2007.

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