Man-made Toxins
We’ve been using oceans as garbage dumps for millennia. As a result, fish are full of PCBs and pesticides. Eating contaminated fish is almost as bad as eating toxins in the original form.
Another man-made toxin (fertilizer) results in ciguatera. Ciguatoxins occur normally, but fertilizers in ocean water cause ciguatoxin creating algae to “bloom.”
Fish, especially reef fish, concentrate it through feeding. Ciguatera causes nausea, vomiting, diarrhea, neurological symptoms, and hallucinations or anxiety. Symptoms may last a few years or for years!