In purse-seine fishing, schools of dolphins are first spotted, indicating to fishermen that schools of tuna are most likely swimming beneath them. The dolphin schools are then chased by small high-speed boats or even helicopters that accompany the fishing boats. When the dolphins begin to tire, the fishermen encircle the school with huge nylon nets that are up to one mile long and 325 feet deep. When both the dolphins and the tuna have been completely surrounded, the bottom of the net is pulled closed, much like a drawstring purse, hence the name purse-seining. Purse-seining has proven to be an extremely effective method of catching fish. Entire schools of tuna are able to be scooped up without a single fish escaping. Unfortunately, many dolphins are also killed in the process, as they become entangled in the nets and drown, or are crushed as the nets are pursed and hauled in.
Use of explosives for fishing in Southeast Asia dates back to World War II, when surplus ammunition became widely available. Application of liquid cyanide, mainly by divers using plastic squirt bottles, to stun large fish such as wrasse, groper and cod so that they can be pried from holes and crevices in reefs, is a more recent innovation.
The use of long lines, that spare the dolphin but kill wandering albatrosses, increases alarmingly. In 1955, Japanese ships catching tuna cast only 20,000 hooks a year into the waters off New Zealand. By 1987 this had risen to 100 million hooks annually. Several 1995 studies showed that the boats around New Zealand alone killed an average of five albatrosses a day. In 1995, one black-browed albatross is killed for every 100 hooks deployed on long lines used for tuna fishing off Uruguay. The long lines were also blamed for a 50 per cent decline in southern giant petrels at Heard Island in the southern extremities of the Indian Ocean.
According to a 1995 report, the groupers, humphead wrasse and other fish taken from coral reefs in the southwestern Pacific Ocean and held in restaurant aquariums were commonly captured by divers who squirt sodium cyanide at them. The chemical - used to execute criminals - merely stuns the fish and is not toxic to people in the dose commonly used for fishing. But scientists have determined that the dose is more than enough to kill the sensitive corals that build the rich reef habitat. According to a 1997 report, hundreds of tons of cyanide was being pumped each year into coral reefs in Southeast Asia, and the annual volume of reef fish caught live in Southeast Asia and the Western Pacific and sold to seafood restaurants in the region was between 11,000 tons and 16,000 tons, worth at least several hundred million dollars.
2. The use of cyanide to catch live reef fish is most intensive in Indonesia and the Philippines. By unfortunate coincidence, these are the two countries whose waters also hold the world's greatest marine biological diversity.
3. While explosives damage sections of a reef, cyanide kills the smaller fish as well as the living coral, algae and invertebrates on which the fish population depends for survival.
4. When a reef is destroyed by cyanide, a whole generation of local fishermen and villagers is being deprived of its main livelihood. The food chain is destroyed from the bottom up, and that means it will take much longer to regenerate.
5. Since Indonesia is so large and the trade in live reef fish so valuable, it is difficult to enforce the laws intended to control it. Local officials are either paid by organizers or middlemen to look the other way, or may even be partners in the business.
6. In Indonesia, it is only illegal to use cyanide for capturing fish. Possession of cyanide on fishing vessels is permitted for 'tranquilizing purposes'. Legal loopholes such as this make law enforcement virtually impossible.
7. Many of the cyanide divers come from poor communities in Indonesia. Those involved in the live trade were paid from US$150 to $500 a month - as much as 10 times the average monthly salary of conventional fishermen and three times that of a university lecturer.