6. Man-made Toxins
For many years now, we have been using the oceans to dump our garbage dumps and as a result, all the living organisms inside the oceans are also contaminated. Fishes are now usually filled with Polychlorinated biphenyl (PCB) and pesticides. Eating contaminated fish is just as bad as eating the toxins in the original form.
Fertilizer releases ciguatoxin in the ocean water which gets concentrated into the fishes, especially reef fish. Eating these contaminated fishes can lead to ciguatera. It causes nausea, diarrhea, vomiting, even neurological problems like hallucinations or anxiety. These symptoms may last for a long time.