A system and method for sorting fish where the system comprises; - a trawl (2) consisting of at least one trawl bag (3, 3', 3"), and where the at least one trawl bag (3, 3', 3") has an opening which covers a part of an inflow area in the trawl (2), - at least one monitoring device (6) arranged in connection with the inflow area and where signals can be transmitted to a processing unit from the at least one monitoring device (6), and - where a device, based on data from the processing unit, can move the opening in the at least one trawl bag (3, 3', 3") to a position where fish flow through the inflow area but on the outside of the at least one trawl bag (3, 3', 3").