ChesMMAP fishes with a 200x12cm, 4 seam, 3 bridle bottom trawl with a 5cm flat sweep (also referred to as "cookie sweep"). This means that the fishing circle of the net is comprised of 200 12cm braided polyethylene meshes. The forward-most panels of the body of the net are made up of 12cm meshes, tapering back to 6cm meshes in the main body and extension. The cover bag of the codend is made of double 12cm braided polyethylene with a 2.54cm knotless nylon liner inserted inside. The trawl doors used are Thyboron Type IV 44", each weighing 120kg in air.
During science operations, trawl monitoring sensors provide near-real-time measures of gear performance, enabling the Captain and crew to adjust tow speeds and scope to obtain the optimum fishing geometry of the net. Equally important, these data are saved to computer files which, when combined with tow distance information from the GPS, allow subsequent data analyses (such as the generation of abundance estimates) to be performed on an area-swept basis. Such analyses provide standard adjustments for tow-to-tow differences in tow speed, tow duration, current speed, and so on.
We use three Simrad PX multisensors - one on each wingend and one on the center of the headrope. This allows us to measure the net width and headrope height in real time to assure the net is fishing properly. Each tow must fall within the acceptable ranges of performance in both of these areas in order to be counted as valid.