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Parental care in the fish world

MANY fishes simply release their eggs and sperm into the water and pay no attention at all to the fertilized eggs, but other fishes build nests and guard the eggs and young.

Fish eggs range in size from barely visible to the size of a coin. Some eggs float in open water, while others are heavier and sink to the bottom. Eggs on the bottom may clump together in masses, or even stick to various objects.

Some fishes place eggs on the undersides of rocks or on sticks in the water. Some eggs simply fall into the spaces between.

Although they pay no attention after spawning, they move to special areas where conditions are just right for spawning and protecting their eggs. For some fish species, this is a matter of moving a few yards in a stream or into shallow water in a lake. But for others it can mean a journey of a thousand miles.

Most fish parents spend little time caring for their offspring. But some will guard their young nestling for a few days after the eggs hatch. In a few species the adults carry eggs on their bodies.

Some fishes actually keep the eggs in their mouths until they hatch. Mouthbrooders are well-known for their ability to care for and protect their offspring by using their mouth as shelter. Some are paternal mouthbrooders and others are maternal mouthbrooders. For mouthbrooders, parental care starts when the eggs are fertilized, and some even extend their offer of shelter after the eggs have hatched. Female African cichlids hide eggs in their mouth for 21 to 36 days. During this time, the female does not eat. When eggs have hatched, she releases her fry. When danger is present, she uses distinct cues to let her young swim back and seek protection.