Evaluation of fish behaviors in response to driven and undriven entanglement nets with emphasis on invasive Silver Carp, Central Missouri, 2015-2016

We used Adaptive Resolution Imaging Sonar (ARIS), which is based on Dual-Frequency Identification Sonar (DIDSON) technology to observe net encounter behaviors of bigheaded carps. Gill nets with four different mesh types (8.9 cm bar mesh) and trammel nets with five different mesh sizes (range 5.1-8.9 cm bar mesh) were evaluated. Net sets were undisturbed, or fish were driven with the noise of the outboard boat motor. We sampled field sites in tributaries and the mainstem Missouri River in central Missouri from June 2015 to October 2016. Specific sampling sites were determined based on previously documented Silver Carp abundance with anticipated densities sufficient for testing behavioral responses to entanglement gears. Specific tributaries sampled consisted of the Lamine River, Blackwater River, Moniteau Creek, and Cedar Creek. Habitat within these low gradient tributaries consists of minimal current if present and shallow depths (less than 4 m). Nets set in the mainstem Missouri River were downstream of channel training structures, where flow diversion resulted in minimal to no current and similar depths. Eighty net sets for 40 hours of total ARIS video were collected. Catch was used to identify length and species present in videos, with Silver Carp and Smallmouth Buffalo the predominate species caught. Within ARIS videos, body morphology was used to categorize and enumerate responses of fish.