50 YEARS OF CYANIDE FISHING: A NOVEL METHOD FOR DETECTION OF CYANIDE FISHING

The illegal practice of using cyanide as a stunning agent to collect fish for both the marine aquarium and live fish food trades continues throughout the Indo-Pacific. Cyanide is destructive to coral reef ecosystems and is certainly one of many anthropogenic causes that has lead to 95% of the reefs in the Indo Pacific to be labeled at risk for degradation and loss. There have been numerous calls to a develop a field-deployable test for detecting cyanide as a means to combat its use. This study represents a first attempt to understand cyanide toxicokinetics after acute exposure in marine fish through direct measurement of the metabolite thiocyanate. Thiocyanate (SCN) was measured in the plasma of Amphiprion ocellaris using HPLC-UV and C30 column pre-treated with polyethylene glycol after acute exposure to 50 ppm for three exposure times (20, 45 and 60 s). Plasma SCN levels observed are dose-dependent, reflecting a longer time for conversion of cyanide (CN) to SCN as the dose of CN increases. SCN plasma levels reached a maximum concentration (1.2 -2.3 ppm) 12 to 20 hours after exposure to CN. The half-life for the elimination of SCN was 1.40 ± 0.44 days for 45 s exposure and 0.44 ± 0.15 days for 20 s exposure. Fish were also directly exposed to SCN (100 ppm for 11 days) and the observed half-life for SCN elimination was 0.35 ± 0.067 days. This suggests that SCN exposure can be used as a proxy for understanding the thiocyanate pathway of cyanide toxicokinetics. If these results can be extended to other species, then plasma SCN concentration could serve as a viable marker for cyanide exposure in marine fish.