the main variation lies in how the large group of tuna is located. There are basically three ways to do this.So the moral here is that dolphins are evil. No wait the moral is that don't look at nice fuzzy sounding phrases like "dolphin friendly" without making an effort to understand what it actually means. I had always vaguely assumed that it meant putting some sort of object on the nets that the dolphins could see or hear and get out of the way but that's not how it works.
1) Get lucky and happen to stumble across a large group of tuna visible from the surface in the middle of an enormous ocean. Obviously, this isn’t terribly practical.
2) Attract tuna using floating objects. Stay tuned, we’ll come back to #2.
3) Follow dolphins, because dolphins in the Eastern Tropical Pacific are often associated with large schools of tuna. Dolphins are easy to follow because, unlike tuna, they have to come up for air.
.......As a result of pressure from environmental activist groups like Greenpeace, it became illegal to fish using method #3, and we now have what is called “dolphin safe tuna”. ..
Recall that method #1 isn’t feasible. Tuna fishing fleets rapidly switched over to method #2, attracting tuna using floating objects.It is poorly understood why fish in the open ocean flock in such huge numbers to floating objects, but is a near universal phenomenon. If you put a log in the middle of the ocean, within hours it will be surrounded by fish.
The big problem with this method is that floating objects don’t only attract tuna. EVERYTHING is attracted to floating objects, including sea turtles, sharks, seabirds, billfish, and, yes, dolphins!
1 hour ago