Sodium cyanide is acutely toxic to any living thing.
Incredibly small amounts of cyanide can kill fish. For example, cyanide measured at 20 to 80 parts per billion can kill rainbow and brown trout. Leftover cyanide at very small concentrations has harmed birds and other wildlife that drank mine pond wastewater. Cyanide can also break down and form complexes with other chemicals or metals and remain as toxic. Mixes of cyanide with other metals and chemicals can be just as toxic as cyanide itself, but they are not routinely monitored or carefully regulated.