Reef fish Reproduction

On the reef, female fish lay eggs that are fertilised by sperm in one of three ways.

• Broadcast spawning - fish in large groups, or in couples, gather after dusk to spawn. The spawning occurs in currents on the edge of the reef or above the reef, so that the eggs are moved quickly away from reef predators.
• Demersal spawning - eggs are attached to coral rubble nests or in burrows or dead shells and then fertilised by males.
• Parental care - eggs and young are brooded in a mouth or pouch (seahorses). Internal fertilisation takes place in sharks and rays.

Most young fish are left to take their chances among the predators - corals, anemones, crabs and bigger fish - on the reef.

Coral Trout Protection

A CRC Reef study into the reproductive behaviour of coral trout has identified specific times of the year and reef locations where spawning occurs. Common coral trout gather in groups at particular sites to mate. The gatherings called spawning aggregations, occur repeatedly for several days over a period of months. While the predictable times and locations may increase chance of reproduction, they may also leave the fish vulnerable to overfishing. Queensland government agencies are using this research as a basis for management of fish spawning aggregations for the Great Barrier Reef Marine Park.