Cyanide fishing

Cyanide fishing is an illegal form of fishing (commonly known as poaching) common in South East Asia, which usually uses the chemical compound sodium cyanide. Since 2000, increasing restrictions on illegal dynamite fishing have led to an increasing growth in this indiscriminate method – particularly as it can be used without generating noise. The use of cyanide as a fishing technique was first documented in the Philippines in 1962. More than 150,000 kg of cyanide is believed to be used in the Philippines annually by the aquarium trade and more than a million kg have been used since the 1960’s

In seawater sodium cyanide breaks down into sodium and cyanide ions. In humans, the latter blocks the oxygen-transporting protein haemoglobin; the haemoglobin in fish is closely related to that of humans, and can combine with oxygen even faster. Through the irreversible combining of cyanide ions onto the active structural domain, oxygen is prevented from reaching the cells, and an effect similar to carbon monoxide poisoning results. Coral polyps, young fish and spawn are most vulnerable; adult fish can take somewhat higher doses. The use of cyanide is known to cause mortality on laboratory corals in measured doses, however this data is very difficult to quantify in regard to wild populations. humans ingestion or breathing in of cyanide leads to unconsciousness within a minute; asphyxiation follows. Lower doses lead to temporary or permanent disability and/or sensory failure. This is a constant danger for the fishermen; there are many local accounts of such "occupational accidents", but such incidents are not recorded in official statistics or statements.

The fishermen dive into the sea usually without artificial breathing aids, although some use illegal and highly-dangerous apparatus whereby compressed air is sent down thin breathing tubes. When they reach the coral reefs, they spray the poison between the individual layers, after which the yield is collected. Edible fish, of which a number are sold for general consumption, are first placed for ten to fourteen days in fresh water for "rinsing". Recent studies have shown that the combination of cyanide use and stress of post capture handling results in mortality of up to 75% of the organisms within less than 48 hours of capture. With such high mortality numbers, a greater number of fish must be caught in order to supplement post catch death.

Colourful, particularly eccentric, and therefore rare coral fish are packed into plastic bags; up to two thirds of these fish die during transport. They are mostly sold to aquariums in the US, Europe and Asia. In the 1990s 80% of the western trade in coral fishes alone came from the island of Palawan in the Philippines. Estimates suggest 70 to 90% of aquarium fish exported from the Philippines are caught with cyanide. Due to the post capture handling stress and the effects of the cyanide, fish are bound to have a shorter life span than usual in our aquariums. According to an interview with experienced aquarium owners, they were willing to pay more for net-caught fish because of the higher survival rate. They also said they would not trust an eco-labelling system, which can be misleading.

The basis for this illegal fishing method is, among others, the rising demand for live fish in the higher-class restaurants of the big cities, particularly in rich, nearby countries, which pay increasingly high prices. The extremely low wages of the fishermen in remote, underdeveloped areas, where there are no alternative sources of income, drive them to endure the health risks and possible prosecution.

Many fishing and diving areas across the whole of South East Asia, already severely damaged from the impact of dynamite fishing, have been ruined or totally lost through cyanide fishing. Many of the slowly growing corals, particularly the dendritic varieties, are a particularly important safe area for young fish and spawn and are now disappearing. Most legal and illegal fishing methods cannot by themselves destroy a stable ecosystem. However, through the effects of synergy, they have led to the almost total breakdown of large coastal areas which were formerly excellent fishing grounds.