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. In 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.