At the end of the 1960s, Peru was one of the most productive fishing nations in the world. The cold waters off its coast, fed by a north-flowing current rich in nutrients, brought an abundance of fish within the range of nearshore fisheries. This enabled fleets in Peruvian waters to make over a fifth of the world's commercial landings of fish. By far the most important catch was of anchovies, which were netted in such huge quantities that the Peruvian economy effectively became dependant on them.
During the 1970s, a drastic change took place. In 1972, the combination of over-fishing and the arrival of an unusually severe El Nino, a recurring climatic phenomenon which severly reduced the productivity of near shore waters, brought about the collapse of the anchoveta fishery. In 1977, the catch was so poor that the fishery was closed down in the spring and banned for the rest of the year.
The collapse os the anchoveta stocks meant that many of those who had depended on the fishery were now forced to look for alternative ways of earning a living. Most moved to other forms of fishing, including longlining and gill netting, for a variety of small fish, crustaceans and molluscs. In the process, they would often accidentally catch dolphins and, rather than waste the bodies, would eat some of the meat. As the meat became popular, some entrepreneurs reasoned that there might be enough of a market to support a fishery directed specifically at the dolphins.
The most frequently caught species is the dusky dolphin, followed by Burmeister's porpoise and the bottlenose dolphin. Most of these are caught, deliberately or accidentally, in gill nets although, in recent years, there has been a sharp increase in the catch of common dolphins, most of which are killed by harpoons thrown from fast boats with powerful engines.
Situations similar to the one in peru may well develop in other Latin American countries and in developing nations throughout the world. As coastal waters become over-fished, larger and more powerful boats are required to enable fishermen to move further our to sea and to catch previously unexploited stocks. However, as more boats appear in the area and competition increases so stocks declines, and the fishermen have to move into still deeper water. This, in turn, gives rise to a further demand for new technology and even larger boats.
Thus begins an ongoing cycle of investment in technology, leading to increased catches, over-fishing and the need for yet more technology. Locked into this cycle, the fishermen, desperate to earn enough money in as short a time as possible to repay the loans on their boats and equipment, and to make some kind of profit, often find themselves forced to take every available resource from the ocean including marine mammals.
This spiralling demand for investment in new technology is further exacerbated by the need for the fisheries of developing nations to compete in a world market against countries with far greater resources. The fate of marine mammals can thus be seen as a small aspect of a large and complex economic, social and politcal situation.