Dolphins are definitely smart but there is much debate over intelligence tests.
Dolphins and porpoises are found in every ocean of the world. From the deep Antarctic Ocean, to South Pacific lagoons, and the bays and fjords of British Columbia's coastline. There are five river dolphin species found in five different rivers. One theory explaining this pairing is that the dolphins and tuna are both feeding on surface-dwelling squids, mackerel and flying fish. When purse-seine fishing nets are set beneath the dolphins to surround the tuna, dolphins and other bycatch also get tangled in the nets and die.