Fish Poisoning and Shellfish Poisoning By Gerald F O'Malley, DO, Grand Strand Regional Medical Center; Rika O'Malley, MD, Grand Strand Medical Center Reviewed / Revised Jun 2022 | Modified Sep 2022 View Patient Education Fish poisoning and shellfish poisoning involve one of several toxins that can cause gastrointestinal, neurologic, or histamine-mediated manifestations.