"The Sole Rope and Cod End" - Trawling for Groundfish
As trawl winches shoot the big heavy net from the back of the boat, enormous metal panels called otter doors help sink the net down to the seafloor. A weighted ground-line called the sole line drags along the sea bottom and a float-covered headline helps to spread the mouth of the net. The otter doors act like kites and hold the net open, while the sides of the net called wings open it even wider. As the fish pass into the gaping mouth they are forced into the cod end, the narrow end of the net holding the catch. Once full, the powerful trawl winches pull the heavy net back to the boat where the stuffed cod end is spilled onto the deck and the catch sorted.
Trawlers drag massive nets with mouths of up to 100 feet (over 30 metres) wide.