I noticed this on a trip to Ganpatipule, a small coastal town in Maharashtra, a few months back.
There was a fisherman wading waist-deep up a creek there, and casting his net about every five minutes. After hauling in his catch, he would carefully separate the fish. He would pick out and release the small young ones (so they could grow and breed to generate a new healthy population) and the inedible ones. The rest i.e. the edible ones would be put into a basket tied around his waist. He must have cast his net at least 20 times, and got a decent amount of fish at the end of the day.
This kind of fishing is currently done on a very small scale. If it could somehow be implemented on a larger scale, for example by hiring a few extra crew members on trawlers to separate the fish and release the unwanted ones, it would definitely reduce the needless destruction of other species, and solve problems like the ones turtles are facing today. Not just that, but by releasing the younger ones, fishermen too can benefit from the healthy population of fish for the next season.