Cyanide fishing
Cyanidfischen a non is selective fishing method , in which mainly the chemical compound sodium cyanide (English: sodium cyanide ) - one with cyanide is used - closely related compound. The chemical solution is brought into the immediate vicinity of the fish by means of equipment, whereupon they become immobile and can be collected.
Cyanide fishing is banned in most countries around the world.
Occurrence
The method is mainly used in Southeast Asia , often as a silent alternative to dynamite fishing , which is also illegal in almost every country in the world. Since the year 2000 it has become increasingly apparent because increased official controls and confiscations make the noisy and sensational dynamite fishing more difficult.
Cyanide fishing occurs mainly in the coastal area (sea) and is aimed at catching tropical fish, which are used as a specialty or as ornamental fish. This method is also suitable for catching classic food fish, but is used less often. The use of cyanide is less effective in standing water (lakes) when cloudiness obstructs the view. The substance has to be introduced in very large quantities and then also endangers the diver, who also depends on good visibility when collecting the fish. In flowing waters, the motionless fish can be collected through nets laid down the river, but the environmental damage is so massive that a section of the river that has been fished cannot be fished again in the foreseeable future. In freshwater, cyanide fishing can therefore only be carried out regionally and only for a very short time; it is more expensive and inefficient. The main occurrences are the extensive coastal landscapes of the East Asian island world.
Scientists at the World Resources Institute (WRI) estimate that cyanide fishermen have released more than 1,000 tons of cyanide in the coral reefs of the Philippines alone since the 1960s . For the Indonesian archipelago, the toxic load is estimated to be even greater. The poisonous plumes often drift through the reefs for days and destroy everything they come into contact with. They kill algae, aquatic plants and contribute significantly to coral death .
functionality
The fishermen often dive into coral reefs without breathing aid, but sometimes also with compressed air (DTG) or through thin breathing hoses, and inject the poison between the individual sticks. The yield is then collected. Edible fish , some of which are overdosed before being sold, are first “rinsed” in fresh water for 10 to 14 days. Colorful, especially unusual and therefore rare coral fish are immediately packed in plastic bags, whereby up to two thirds perish on the transport routes. They are intended primarily for aquarists in the USA, Europe and Asia. In the 1990s, 80 percent of the coral fish in western trade came from Palawan alone .
The reasons for this illegal fishing method include: a. the increased demand for live fish in better restaurants in big cities - increasingly in financially stronger, nearby countries - for which considerably higher prices are achieved. The extremely low wages of the fishermen in unstructured, remote areas, which offer them no alternative income, force them to accept the health risks and possible convictions by law enforcement agencies.
Many fishing areas and diving spots throughout Southeast Asia, which had previously been severely damaged by dynamite fishing, were severely destroyed for years to the point of total loss. Many of the slowly growing corals , especially the branched coral types, are an important protected area for young fish and fry and are now missing. Most legal and illegal methods in themselves cannot usually destroy a stable ecosystem. However, there are synergy effects , as a result of which fishing has almost completely collapsed in large, coastal areas of formerly excellent fishing grounds.
Chemical basics
In water and in seawater , sodium cyanide dissociates into sodium and cyanide ions . In humans, the latter block the Fe (III) ions of the enzyme cytochrome oxidase, which means that oxygen can no longer be transferred between the hemoglobin and the cells and vital cell respiration is interrupted. Fish only react in the same way at slightly higher doses; coral polyps, fry and fry are more sensitive. In humans (a direct danger for fishermen), unconsciousness occurs after a minute if the hydrogen cyanide vapors are inhaled directly or if seawater is accidentally swallowed, as often happens with divers. Then the “internal” suffocation takes place. Lower doses lead to temporary or permanent paralysis and / or sensory deficits. Many such "accidents at work" are described on site, but they do not appear in any statistics or official statements.
The effect is reversible in fish. The cyanide can be excreted from the metabolism of an anesthetized fish after a recovery phase, so that the animal recovers. The amount of cyanide ions absorbed is decisive. If it is too high, the fish dies later because its organs show too much cell damage. With a low dose, the fish can fully recover. The dosage can only be controlled poorly by the diver, because the cyanide solution is distributed unpredictably through eddies in the water.
References
Web links
- Dynamite & cyanide , illegal trapping methods using the case study Palawan , Philippines (Klaus Polak)