Some fishing techniques, like the drift nets yield not only tons of fish but kill millions of birds, whales and seals and catch millions of fish not intended. Small net holes often capture juvenile fish who never have a chance to reproduce. Millions of fish may be killed because of being caught by lost or abandoned fishing equipment. Some forms of equipment destroy natural habitats, for example bottom trawling may destroy natural reefs. Other destructive techniques are illegal dynamite and sodium cyanide fishing that kill or stun reef fish so that they can be caught quickly in large quantities (the latter killing coral reefs and few months later also the captured goldfish).
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.
Cyanide fishing for live reef fish encompasses a swath from the Maldives in the Indian Ocean to the Solomon Islands and Australia in the Pacific, according to the report – a range equivalent to about a quarter of the earth's circumference, containing the biologically richest one-third of the world's coral reefs. It is generally illegal to use poison in fishing throughout this region.
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.
Every year, approximately 20,000 dolphins are believed to die in purse-seine nets. The method of fishing is especially predominant in the Eastern Tropical Pacific Ocean, a region which extends from southern California to northern Chile.The primary species of dolphins that are affected include spotted, spinner and common dolphins. Purse-seining is believed to have dramatically reduced populations of these species.
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.
Fish stunned by cyanide and shipped live to Chinese seafood restaurants – in Hong Kong, China, Taiwan, Singapore and other countries in an increasingly affluent region – have many times higher prices than the same fish chilled, frozen or even farmed. For example, a single Napoleon wrasse smuggled out of Indonesia, where its export has been illegal since 1995, can sell to eager seafood customers for over US$5,000, including up to $245 for the lips alone, which are prized as a particular delicacy. Large fish destined for the restaurant trade are generally able to pass cyanide poison out of their systems when put in holding pens before shipment.
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.
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.
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.
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.
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.
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.
It is true that fishermen and their equipment have become dangerously powerful. But all evidence available in 1995, including that from the UN Food and Agriculture Organization, indicates that the ocean is relatively healthy. The processes that create food in the sea are largely intact.