Oviparous fish as a rule spawn only once a year. The little
phycis or black goby is an exception, as it spawns twice; the male
of the black goby differs from the female as being blacker and
having larger scales.

Fishes then in general produce their young by copulation, and
lay their eggs; but the pipefish, as some call it, when the time of
parturition arrives, bursts in two, and the eggs escape out. For the
fish has a diaphysis or cloven growth under the belly and abdomen
(like the blind snakes), and, after it has spawned by the splitting of
this diaphysis, the sides of the split grow together again.