Novel Trawling Techniques Capture Juvenile Silver Carp in the Illinois River

Techniques that effectively capture all sizes of invasive carp are integral to addressing management of these nuisance fish. The Columbia Fish and Wildlife Conservation Office developed the surface trawl and dozer trawl to target juvenile invasive carp.  Both trawls were utilized in 2015 Illinois River monitoring efforts to detect juveniles less than 150 millimeters (mm).  The surface trawl is a large conical net pulled behind the boat with towlines attached to trawl doors.  It is best utilized in open water greater than one meter deep with low flow.  The dozer trawl can be used to sample small, shallow backwater habitats as well as swift main channel borders.  It is a simple, inexpensive adaptation to existing boats.  A conical net is attached to a rigid, rectangle frame pushed in front of the boat sampling up to 1 meter deep. Of the 330 Silver Carp ranging from 33 to 635mm captured in 2015 by surface trawl, 92% were less than 150mm. The dozer trawl captured 124 Silver Carp ranging from 51 to 750 mm, of which 96% were less than 150mm.  In addition to detecting juveniles, potential applications for these innovative techniques include monitoring year class production and removal of young-of-year.