Barbasco, fish poison (need Latin name)

I don’t yet have a Latin name for this plant. The common name is Barbasco. The locals on an island I’m working on use it occasionally as fish poison. The leaves are crushed and the liquid collected. The liquid is then dropped into relatively still water killing the fish (and whatever other marine dwelling creatures are in the vicinity) which float to the water’s surface and are collected. Apparently, the toxicity of the plant doesn’t affect humans when the fish is eaten.