Nest Guard Replacement in the Antarctic Fish Harpagifer bispinis: Possible Altruistic Behavior.

Nesting biology of the Antarctic plunder fish, Harpagifer bispinis (Schneider), was examined at Arthur Harbor, Antarctic Peninsula, during the austral winter, 1975. Females prepare nest sites, spawn, and guard the eggs for 4 to 5 months, the longest guarded incubation period reported for any fish species. If this guard is removed, it is soon replaced by a conspecific, usually male. If the second guard is removed, a third replaces it. Guards are essential to ensure nest survival. Selfish or parental acts or acts of kinship or reciprocity do not adequately explain guard replacement. The act may be altruistic.