A new scientific study in the journal Clinical Toxicology reports on two men who suffered long, bad trips after eating Sarpa salpa fish in Mediterranean restaurants. This kind of hallucinogenic fish poisoning, called Ichthyoallyeinotoxism, was previously only reported in the Indo Pacific. From Practical Fishkeeping magazine:
The effects of eating ichthyoallyeinotoxic fishes, such as certain mullet, goatfish, tangs, damsels and rabbitfish, are believed to be similar to LSD, and may include vivid and terrifying auditory and visual hallucinations. This has given rise to the collective common name for ichthyoallyeinotoxic fishes of "dream fish"...
Indoles, with similar chemical effects to LSD (lysergic acid diethylamide) are believed to be responsible and may be consumed when the fish eat algae or phytoplankton containing the chemicals. All of the species effected by ichthyoallyeinotoxism are algal grazers.
Others have claimed that different species of ichthyoallyeinotoxic fishes, such as Kyphosus fuseus, contain much more potent hallucinogens, such as dimethyltryptamine or DMT, which is considered to be one of the world's most mind-bending hallucinogenic chemicals.