Pantropical spotted dolphin  (Stenella attenuata)

The tendency of the pantropical spotted dolphin to associate with tuna schools has been this species’ downfall in the eastern tropical Pacific. Fishermen take advantage of this association to help them locate and catch tuna more efficiently (4), and will intentionally capture both tuna and dolphins together, then release the dolphins from the net (6). Either the dolphin is killed in the process, or this can lead to a single dolphin being chased, captured and released many times during its lifetime, causing a great deal of stress (6).

In the eastern tropical Pacific, tuna fisheries have killed millions of dolphins since the 1960s (2) (5), reducing some stocks to a fraction of their former size (2). Today, mortality rates have been greatly reduced, yet the populations are not recovering from this devastating exploitation as well as could be expected; the stresses of being repeatedly chased and captured, as well as separation of mothers from their young, are possible reasons cited for the slow growth of the populations (5).

Pantropical spotted dolphins are also hunted intentionally in some areas, such as in Japan, Solomon Islands and the Philippines, where they are caught for human consumption and fishing bait (2) (5). They are also taken as bycatch in many fisheries in developing countries around the globe, and in some countries, such as Peru, Ghana and the Philippines, the bycatch is kept and used for human consumption. This has lead to the evolution of directed catches as the markets for the meat develop, resulting in a growing conservation problem (2).

Once it had been noticed what enormous numbers of dolphins were being killed in tuna fisheries in the eastern Pacific, actions were implemented to try and reduce these unnecessary deaths. In the 1970s, the United States employed laws and measures aiming to reduce dolphin bycatch to levels approaching zero through improved fishing methods (6). In 1979, the Inter-American Tropical Tuna Commission began a dolphin conservation program, and soon, the idea of dolphin-safe tuna became popular, with the United States only allowing the sale of dolphin-safe tuna by 1994. In 1999, the International Dolphin Conservation Program Agreement came into force, which meant the major tuna fishing countries in the eastern Pacific were bound to certain measures such as having observers on boats and strict dolphin-mortality limits. As a result of all of these actions, dolphin mortality has fallen drastically (6), which will hopefully give the pantropical spotted dolphins, and other dolphin species, a much needed opportunity to recover.