Why do young Arapaima gigas gather around the male’s head?

Young Arapaima gigas (also known as the pirarucu) congregate around the male’s head primarily for protection and cohesion during their early development. This behavior is driven by several factors:

• Camouflage: During the period of parental care, the male’s head turns a dark, grayish-black color, which provides effective camouflage for the dark-colored young, helping them hide from predators.12
• Visual Stimulus: The dark coloration of the male’s head serves as the primary visual stimulus that encourages the young to form and maintain a shoal around him.1
• Chemical Signaling: It is believed that the male releases a secretion from glands located on his head that provides a gustatory (taste) or olfactory (smell) stimulus, further attracting the young and keeping the group together.1

The male provides this care for approximately two to three months after the embryos hatch and leave the spawning pit. If the male dies during this period, the young will typically join other shoals.1