Assessing the effectiveness of drop chain footgear at reducing bottom contact in the Newfoundland and Labrador shrimp trawl fishery

This study compared the effectiveness of a reduced seabed impact footgear versus a traditional rockhopper footgear on identical bottom trawls targeting northern shrimp (Pandalus borealis) in Newfoundland and Labrador, Canada. The experimental trawl used in this study was designed to be low seabed impact through the reduction of contact area of the footgear by replacing traditional heavy rockhopper footgear with only a few drop chains lightly in contact with the seabed (i.e., drop chain footgear). Two variants of the experimental drop chain footgear (9-drop chain and 5-drop chain) were designed, evaluated in a flume tank to estimate contact area with the seabed, and then briefly tested at sea for engineering performance and catchability. Results from the flume tank tests were encouraging, demonstrating that the traditional and experimental trawls were similar in performance, but with the experimental drop chain footgears producing substantial reductions in the predicted contact area with the seabed. Comparative commercial fishing trials were then subsequently made with a total of five pairs of tows (10 tows) for the 9-drop chain and six pairs of tows (12 tows) for the 5-drop chain. Though only briefly tested at sea, the results revealed that the drop chain footgears were promising in both engineering and catch performance. Underwater video observations demonstrated that the drop chain trawling system, with greatly reduced bottom contact on the seabed, could help reduce potential disturbance of marine ecosystems, in particular minimizing encounters with snow crab (Chionoecetes opilio).