The Use of Positively Buoyant Ground Cables and Sweep to Reduce Seabed Contact and to Enhance Species Selectivity

A groundfish net was modified to limit its bottom contact and to improve escapement of bottom-tending fish species. A model was first evaluated in the flume tank facility of Memorial University, followed by field trials. Two trawl configurations were tested against a Control, during fishing experiments in 2007 and 2008. In the first configuration, the goal was to fish the net approximately 1.5' off the seabed, to retain cod and haddock while reducing catches of flounders and other demersal species. In the second rig, the Experimental trawl was fished up to 3' off the seabed, to retain haddock while reducing catches of cod, flounders and other demersal species.

Flume tank tests indicated that a stable condition and proper fishing heights were achieved with a combination of floats on the headrope, footrope and ground gear, combined with weights attached to the wing ends. Field trials followed the recommendations developed in the laboratory, and video observation revealed a stable fishing condition, with little contact with the seabed. Catch information was hampered by low fish availability, but indicated that the correct escapement pattern was occurring, with the exception of higher-than-desired escapement of haddock during the second experiment.