The right option is; b. Trawling gathers fish indiscriminately.
Trawling gathers fish indiscriminately best explains the environmental problems associated with trawling.
Trawling is a method of fishing in which cone shaped fishing nets that are produced from two or more panels are pulled by one or more boats (trawlers) through the water (in the middle or on the bottom). Trawling is non-selective and it captures and removes fish indiscriminately from the water. It gathers small sized species, marketable, and unwanted or non-target species of both legal and illegal size. Trawling can accidentally kill valued species such as sharks and dolphins in water.