" The Controversial Use of Cyanide"
Cyanide is a deadly poison. Like a gun, it is dangerous in the hands of the wrong person, whether that person be a collector or a writer. For too many years, articles in aquarium magazines have deplored the collection of marine fish with cyanide for two reasons, one true and the other false. That cyanide is destructive to the reefs is absolutely true. What isn't true is that fish collected with cyanide will eventually starve and die. In fact, fish collected with nets will also starve and die, as we'll see later.
Cyanide is a cheap, common industrial chemical used in gold mining, electroplating and steel mills. Free cyanide (CN-) can bind with many common metals, including substances we normally think of as salt constituents. When the relatively safe potassium salt of cyanide is mixed with an acid, the two react to release a deadly hydrogen cyanide gas which causes rapid asphyxiation. Waste industrial free cyanide, when released into the environment, binds with waste industrial metals like nickel, zinc and copper or with common environmental metals like potassium and sodium. It can also react with industrial chlorine compounds to produce toxic cyanogen chloride and other noxious substances at a very high pH. In short it can be safe when a salt, but deadly as a gas or a chlorinated liquid.
How does it work? Hydrogen cyanide gas interferes with the enzymes which facilitate oxidative phosphorylation, the mechanism by which we store energy in phosphate bonds for later use to drive metabolic reactions. In biochemistry, we indicate a high energy phosphate bond as ~PO4 or just ~P for short. The enzymes required to store energy in phosphate bonds depends on oxygen, and that's why the process is called phosphorylation. Tehre are two steps. In the first step, we take adenosine monophosphate ( AMP or A-P) and add one high energy phosphate bond, forming adenosine diphosphate (ADP or A-P~P). In the the second stage we add another ~P to form adenosine triphosphate (ATP or A-P~P~P). The tail end ~P of ATP is unstable, easy to save and easy to spend. Many of our body's chemical reactions give up that last ~P to fuel the reaction. Cyanide throws sugar in our gas tank, locking up the engine that makes us go.
As with all drugs, the effect of acute (sudden exposure) cyanide poisoning depends on the dose. At very low doses, there is no effect. At higher doses, the cyanide causes a shutdown of much of the animal's oxidative phosphoylation ( adding that final ~P to ADP to make ATP). The animal passes out and may die within minutes. At still higher doses, all oxidative phosphoylation shuts down and the animal rapidly dies. How much is anaesthetic and how much is lethal? As with all drugs, it depends on age, species, metabolic rate, body weight of the animal and contact time. Some animals require a huge amount for anaesthesia, while others are killed by very small doses. Fishery biologists in the past sometimes used cyanide as an anaesthetic for some species of fish at carefully controlled doses. As with all medications, an important measure of safety is the difference between the effective dose and the toxic dose. (That difference is one basis for deciding whether a medicine should be available over the counter or only by prescription). Because the lethal dose is only slightly higher than the anaesthetic dose, cyanide is not a safe anaesthetic even under labor
atory conditions. Therefore, fishery biologists usually use much safer anaesthetics such as MS-222 or quinaldine.
Following World War 2, dynamite was widely used in some parts of the Pacific to break up nearshore coral reefs as a source for building and construction. Dynamite also stuns fish, and commercial fisherman in many areas adopted it as a more effective in deep water than traps or hook and line, in locations where they could not use nets which hung up on corals.
Many governments appalled at the destruction of the reefs for such a low return product as fish (vs. a high return product such as construction) banned the use of dynamite for fishing. Not to be thwarted, fisherman then adopted the use of cyanide to collect fish. It was cheap and, more importantly, silent, so that its use a mile off of the beach would not attract attention from the local authorities. In some cases where there were no mining or industrial operations nearby to supply the cyanide, the foreign fish buyers provided it. The product was clean, unmarked and the market was growing with development around the Pacific- rim.
Fresh caught fish must be iced for holding and transport, or shipped very quickly to the end user. In the last decade, fresh fish prices have been dwarfed by the price paid for live fish. Today in Hong Kong, Singapore, Taiwan, Japan, South Korea and even Beijing, restaurant windows feature live animals in aquariums and terrariums. Passers by note what is in the window, enter the restaurant and order that live animal for lunch or dinner. The assortment is mind- boggling, including farm raised tilapia, eels, foxfaces, groupers, grunts, snappers, wrasse, parrotfish, tangs, turtle and even American largemouth bass and bullfrogs. Locales in the central Pacific, including some portions of the Philippines and Indonesia, are major suppliers of reef fish collected, legally or otherwise, by cyanide. Fish that die are used locally or frozen for export, while survivors are shipped to newly emerging economic powerhouse cities in live tanks where they demand a much higher price.
Cyanide collecting of marine fish for food or the aquarium market is still practiced in many places in the low wage countries of the western Pacific where net, traps, hook and line, and aquaculture are increasing. It, nevertheless, difficult to assess whether a box of fish brought to a buyer anywhere was collected by net, trap, bleach, cyanide, quinaldine, or even puffer poison. The only way to be certain is to go out with that collector, and in many cases, that is not feasible or the buyer doesn't want to know. What are the consequences of chemical collecting? It is undeniable that bleach, cyanide and quinaldine are cost- effective at anaesthetising fish or chasing them out of holes. The downside of collecting fish in this manner are several. First, the dose is uncontrollable because concentrated drug is squirted from a plastic bottle to inside or outside a hole with very varied currents. Fish of different species and sizes have different susceptibilities, respond to different contact times, and many will die almost immediately. More important are the effects on invertebrates, which are in some cases more susceptible to than fish. Tubeworms can withdraw and, in the process, rapidly flush out, or otherwise avoid a noxious chemical, but coral polyps have no such defence. The effects of cyanide collecting on coral reefs have been documented to be devastating to the corals and other marine life.
But what about small tropical marine fish collected in the central Pacific with cyanide and shipped to the American aquarium market? Following a series of articles in FAMA by Steve Robinson and others a few years ago, a mass hysteria raced through the marine industry fed by anecdotes passing as science, authors promoting themselves as authorities, and defensive exporters with their livelihoods at stake, testifying with as much credibility as a criminal. The low point occurred when the same people raising the hue and cry against cyanide collecting began hawking at their own cyanide free, net caught fish, mixing their message with commercial self promotion. The FAMA series by Steve Robinson identified a so called cyanide syndrome characterised by a failure to eat or by a ravenous appetite, swelling, an exudate from the intestine, and death within four to six weeks. It was said that 80% of delayed aquarium fish mortalities were due to cyanide collection. Finally another published report described sloughing of the intestinal epithelium. This seemed to explain the exudate, the starvation with or without feeding, and the delayed mortality. Contributors of this series of observations, in addition to Robinson, were Herwig, Rubic and Bellwood, and FAMA was the place to get the scoop.
What was missing from the hoopla was science. Experiments were conducted without controls. Pathological changes were reported by non- pathologists, and the medical and biochemistry literature was dismissed as irrelevant because it didn't support the anecdotes. In 1995, D. R. Bellwood, one of the contributors to the early erroneous information did penance by essentially retracting his earlier findings in a new report, this time in a scientific journal (Hall & Bellwood, 1995, Journal of Biology, vol 47, pp 438- 454). This time, controlled studies were conducted of cyanide exposure, stress and gut epithelium in Pomacentrus. The results were as revealing as the analysis was thorough. There were no changes in gut epithelium associated with anaesthetic cyanide exposure (10ppm for a minute and a half). The mortality of fish exposed to anaesthetic doses of cyanide was the same as the mortality of net caught fish. Gut epithelium changes were associated with starvation, and starvation alone, as has been reported in many other fish. Withholding food alone did not kill any more fish than controls, as fish could tolerate extended starving. High mortalities were associated with stress. The highest mortalities were associated with both starved and stressed. (Stress was the removal of hiding places comparable to holding fish in pet stores in bare tanks.) The mechanism by which stress enhances mortality were not discovered, but there was no evidence that anaesthetic doses of cyanide caused either gut epithelial changes or more mortality than occurred with net caught fish.
Are wild marine fish from some localities more likely to die than those collected from elsewhere, and is it due to cyanide vs. net collecting? The answer is a resounding yes and no. Yes in that some places are riskier than others as sources of healthy marine fish. And no, in that net collecting marine fish doesn't deliver healthier fish than collecting with cyanide based on the evidence to date. Then what kills fish? The answers are stress, stress and stress. Stress when they are collected, stress when they are stored or shipped and stress when they are placed in new tanks in shops or homes. Recently one television programme featured a couple of collectors in Hawaii, lauding their environmentally conscious use of nets and their care in removing gas from the swim bladder with a hypodermic needle. What was not explained was why these fish needed to be degassed with a needle rather than decompressed by bringing them to the surface slowly as is done elsewhere. The collectors claimed a mortality of much less than 1%, hyperbole so bizarre as to throw credibility of everything else they say into doubt. A dozen years ago, I visited a one man net collector at his facility, a mobile home up slope and a large tank lower on the beach. This tank was so filthy, turbid and crowded, that I wondered if he had ever changed any water. And that was in Hawaii, USA, my friends.
Wild fish can be exposed to many stressors between the time they are caught and the time they get to your aquarium. They can include days or weeks of starvation, sudden cold or very hot temperatures, oxygen deprivation, ammonia or nitrite build up, rapid pH shifts, sudden exposure to bright light, no hiding places, being chased, bitten, scratched, cut stung and beaten with hard containers and nets. And don't forget degassing with a hypodermic needle.
Net collecting is preferable to chemical collecting because it damages ancillary damage to reefs. But collecting with traps, such as pipes and cans, can also be harmless to the reef and produce less stress on captured fish than chasing them with a hand net across sharp rocks and into an entangling and cutting gill net. The idea that Philippine, Indonesian or Ceylonese fish are inferior to Hawaiian or western Pacific fish because of cyanide is unwarranted. If the fish from any supplier anywhere are inferior, it is because of collecting and handling and difficulties in shipping. If your fish doesn't eat and starves to death, stress or diet may be the cause. If it dies for no apparent reason, look to stress, temperature, water chemistry, competition or an inappropriate diet.
Blaming deaths on cyanide use in some parts of the world, as bad as it is to reefs, is a red herring.
Reproduced from an article by Robert Goldstein in the October 1997 edition of Freshwater and Marine Aquarium magazine
