Each pays little heed to man-made boundaries and passes unhindered from national to international waters, making their management contentious and difficult. As for you and me and Charley, spending a portion of my life pouring through several pounds of reports, press releases and treaty-related documents on tuna and dolphin has made it much easier to forsake eating of most kinds of tropical seafood. For those who realize that fishing will continue yet still want to try and reduce the messier aspects of predator relations via international cooperation, the proposed changes are the way. The objects at the lower right are small boats that help distribute the nets. When the circle is complete, the bottom of the net is closed, trapping all sea creature within.
Water pressure causes the net at the point to drop, allowing the dolphins to escape.
The tuna, which typically swim several hundred feet below the surface, are still trapped. These dolphin have just escaped from the seiner net. It's always questionable to attribute human emotions to other species, but one imagines that these dolphins are happy to be free. Tuna seiner pulling in a full net - minus dolphins.