The half-life of cyanide in the blood of the marine fish, Amphiprion clarkii after cyanide exposure

Abstract

Cyanide fishing continues to be used in the Indo-Pacific region to capture live reef fish for use by the live fish food and marine aquarium trades. The deliberate release of this broad-spectrum poison in reef environments is one of many anthropogenic threats to coral reefs today. Although this capture method is illegal in most countries, regulating its use is challenging due to the difficulty in determining whether a fish was captured using cyanide. A reliable method to test if marine fish have been caught using cyanide has long been the goal of the marine aquarium trade, but to date no test has been validated on fish with known cyanide (CN) exposure. Additionally, there are little to no toxicokinetic data on CN metabolism following CN exposure for marine fish. In this study, we exposed 38 specimens of Amphiprion clarkii to cyanide (50 ppm for 45 s) and measured the concentration of cyanide in their blood over time to characterize the detoxification process. CN was isolated from the blood by microdiffusion and derivatized to the highly fluorescent ẞ-isoindole and then quantified by HPLC. The half-life of cyanide in the blood of the marine fish A. clarkii was found to be 3.1 ± 2.0 hrs. CN levels were seen to be slightly above control levels 1 day post exposure and below control levels 3 days post exposure suggesting that any test for CN exposure by measuring cyanide must be conducted soon after exposure. To our knowledge, this is the first direct measurement of cyanide in the blood of a marine fish following CN exposure.