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Parental care in the fish world

Live-bearing fishes are those that, like humans, give birth to live offspring. Mating is necessary for live-bearing fish; the female fish is internally fertilized by the male fish, and carries the fry for about a month before delivering them. Upon delivery, the babies swim off, hide, and begin searching for food.

Bubblenest builders lay their eggs in a nest of bubbles blown by the male fish. The bubbles are held together with saliva and look like foam. The male tends the nest, blows bubbles as they pop, and keeps any falling eggs or fry in it. He will also defend the nest against other fish.

A common setup among cichlids is to have both fish guard and care for the young. The parents will take turns fanning or blowing fresh water onto the eggs. Once the eggs have hatched, the parents will also guard the fry. Some will even move the fry to a different place each day. Once the babies are free swimming, some fish continue to guard them, while others end their parental duties.

Discus fish, a genus of cichlids, feed their babies off of their slime coats. Parents produce a secretion through their skin which young feed on until they are big enough to forage. Researchers have discovered that discus fish parent like mammalian mothers. Not only do the parents feed their young from mucus secreted on their surfaces, but the nutritional and immunological content of the mucus changes as the young develop, much like mammalian milk. The fry feeds on their parents’ mucus up to 10•min by biting at the parent’s side until the parent expertly ‘flicked’ the shoal over to its partner to continue feeding. The parents diligently feed their young intensely for 2 weeks.

However, 3 weeks after the fry bites less and less, and investigates other food sources.