Where any draft net is used in the course of any fishing operations conducted by means of a boat used for commercial fishing and any trout of a size less than 35.5 centimetres, or pollen of a size less than 20.5 centimetres, is taken on board, the master, owner, charterer or other person in charge of the boat shall cause such trout or pollen to be returned immediately without avoidable injury, to the water from which it was taken.