Trawl nets are large fishing nets designed to catch fish and other marine creatures. They are typically towed behind a boat, known as a trawler, which drags the net through the water. The net has a wide opening at the front to capture fish and a narrow end, called the codend, where the catch is collected. These nets can be used at various depths and are effective for catching different species, including shrimp, cod, and herring. However, trawl nets can also unintentionally capture non-target species, leading to concerns about bycatch and its impact on marine ecosystems.