Influence of Throat Configuration and Fish Density on Escapement of Channel Catfish from Hoop Nets

Authors

Mark T. Porath, Nebraska Game and Parks CommissionFollow
Larry D. Pape, Nebraska Game and Parks Commission
Lindsey K. Richters, Nebraska Game and Parks CommissionFollow
Kevin L. Pope, University of Nebraska-LincolnFollow
Mark A. Pegg, University of Nebraska-LincolnFollow

Date of this Version

2011

Comments

Published in American Fisheries Society Symposium 77:563–571, 2011. Copyright © 2011 by the American Fisheries Society. Used by permission.

Abstract

In recent years, several state agencies have adopted the use of baited, tandemset hoop nets to assess lentic channel catfish Ictalurus punctatus populations. Some level of escapement from the net is expected because an opening exists in each throat of the net, although factors infl uencing rates of escapement from hoop nets have not been quantified. We conducted experiments to quantify rates of escapement and to determine the infl uence of throat configuration and fish density within the net on escapement rates. An initial experiment to determine the rate of escapement from each net compartment utilized individually tagged channel catfish placed within the entrance (between the two throats) and cod (within the second throat) compartments of a single hoop net for overnight sets. From this experiment, the mean rate (±SE) of channel catfish escaping was 4.2% (±1.5) from the cod (cod throat was additionally restricted from the traditionally manufactured product), and 74% (±4.2) from the entrance compartments. In a subsequent experiment, channel catfish were placed only in the cod compartment with different throat configurations (restricted or unrestricted) and at two densities (low [6 fish per net] and high [60 fish per net]) for overnight sets to determine the infl uence of fish density and throat configuration on escapement rates. Escapement rates between throat configurations were doubled at low fish density (13.3 ± 5.4% restricted versus 26.7 ± 5.6% unrestricted) and tripled at high fish density (14.3 ± 4.9% restricted versus 51.9 ± 5.0% unrestricted). These results suggest that retention efficiency is high from cod compartments with restricted throat entrances. However, managers and researchers need to be aware that modification to the cod throats (restrictions) is needed for hoop nets ordered from manufacturers. Managers need to be consistent in their use and reporting of cod end throat configurations when using this gear.