Hrmm... very first link on a google search:
"No data exists on the sexuality of the dartfishes (e.g., are they gonochorists or hermaphrodites?) and little information is available on their reproductive behavior and mating systems. However, many species apparently form long-term pair-bonds. Dartfishes lay demersal eggs in the burrows in which they refuge, and upon hatching the larvae enter the plankton to drift and develop without further parental attention. The juveniles settle-out of the plankton at about 2.5 cm (1 in.), at which time, many species will immediately form schools for protection"
A deep dive with the fascinating dartfishes, genus Ptereleotris: ideal reef aquarium fishes
www.reef2rainforest.com