Trawling is a method of fishing that works by pulling a large fishing net through the water behind one or more boats. Although trawling is a very effective technique, it can be very destructive, since it sweeps up both desirable and undesirable fish (the "bycatch"), and bottom trawling, the dragging of nets along the seafloor, destroys the habitats of many important organisms living on the bottom.
Although trawling is heavily regulated by governments, it remains the target of many protests by environmentalists.
"Trawling" has come to be used in a number of non-fishing contexts, generally referred to indiscriminate collection with the intent of picking out the interesting bits. For instance, in law enforcement it may refer to the practice of collecting large records of phone calls in the hopes of finding calls made by suspects.