Myth. Jatropha is not harmful to fish.

Fact. Jatropha bark is popularly used as fish poison. Research by
German scientists have shown that common Carp (Cyprinus carpio L) is
very sensitive to phorbol esters of Jatropha. Large scale plantation
on Jatropha specially near water bodies may cause great harm to fish
species. Detailed studies are required before starting such
plantations.