Methysergide is considered to be a hallucinogenic drug in humans. Just as a larger dose of methysergide is needed to elicit the fish surfacing reaction, a larger dose of methysergide is needed for human effect.
The LSD-like fish surfacing reaction is also observed for MLD-41, which is similar in its structure to LSD, the only difference being that MLD-41 contains one methyl group more than LSD.
Gettner H. H., A. Rolo and H. A. Abramson (1965). Lysergic acid diethylamide (LSD 25). 36. comparison of effect of methysergide (UML 491) on goldfish and siamese fighting fish. The Journal of Psychology 61, 87-92.