The Short Version
No confirmed catch or sighting of the poisonous rabbitfish (Lagocephalus sceleratus) has occurred in Bulgarian waters. The claim appears to stem from a conflation: viral reports show Bulgarian citizens catching the fish while fishing in Greek waters, not in Bulgaria. Authoritative Bulgarian outlets, including Factcheck.bg, explicitly note the absence of verified Bulgarian records, though experts warn the species could eventually spread given its documented presence elsewhere in the Black Sea.