Good article, Thanks!
A quote from it:
How can you tell?
Generally, fish caught with cyanide look as normal as the others. But try to look closer and observe their movement. Perthaquarium.com names two signs:
“Erratic looping movements or continuous, repetitive nervous circling and secondly, a suppressed appetite. This is in fact their temporary reprieve; which is why it is important to only purchase full-bellied fish which are accepting food. Often it is the cyanide caught fish’s first meal that triggers their ultimate demise. Their damaged kidneys and liver are unable to perform detoxification and the fish is poisoned by it’s own wastes.”
Another sign would be the surprisingly low price of the fish. “If a fish is being sold at a bargain price, and the store isn’t running a sale, then the fish probably isn’t a bargain at all,” warns Aquariumpros.com. Because a diver who uses drugs to catch fish can catch more per hour, cyanide and drug-caught fish will always be cheaper (and die sooner) than hand-caught fish. So it pays to always question the health of an unusually inexpensive specimen.
Cyanide poisoning breaks down enzymatic systems that metabolise oxygen in the blood. Eventually it means that oxygen won't reach the liver, heart, brain, and other organs of the fish. Basically they suffocate from the inside. The most obvious symptons are heavy/fast respiration and lethargy.