Fish Spawning Aggregation Sites On The Great Barrier Reef

Fish spawning aggregation sites (FSAS) are places on the Great Barrier Reef (GBR) where many species of tropical reef fish gather at specific times to spawn.

Spawning aggregations are influenced by seasons, lunar phases and temperature. Fish usually aggregate at places with specific characteristics. Research suggests that water movements at these locations transport eggs and larvae into the water column to assist the pelagic phase of development. The characteristics of the site may also facilitate male and female-spawning interactions. For example, the sites favoured by common coral trout Plectropomus leopardus, provide refuge for females to hydrate eggs and rest from the attention of males.

In recent years, spawning aggregations of 49 fish species have been reported in the Great Barrier Reef Marine Park (GBRMP). Aggregations of an additional 84 species that occur on the Reef have been reported elsewhere within their geographical range. Fishes that participate in these aggregations range from predatory serranids, trevallies and snappers, to herbivorous parrot and surgeonfish. Research shows that spawning aggregations occur in at least 21 families of tropical reef fish worldwide, and that all of these species produce pelagic eggs.

The frequency and type of spawning aggregations can vary considerably both within and between fish species. Aggregations may form on a daily basis with associated movements over a short distance (resident), or on a seasonal basis, as a result of large-scale migrations (transient).

Investigations of the spawning patterns of the common coral trout on the Great Barrier Reef have revealed there are two different types of aggregation sites - primary and secondary. During the spawning season most common coral trout gather at one primary location on a reef, however some fish will visit the secondary sites where smaller groups are spawning. Formations of spawning aggregations at primary sites are highly predictable from year to year, whereas formations at secondary sites seem fairly random.

The GBRMPA report Spawning Aggregations of Reef Fishes on the Great Barrier Reef: Implications for Management, discusses fish spawning aggregation sites and the human impacts on these aggregations. The report discusses management options to ensure the continued spawning success of aggregating fish on the Great Barrier Reef.

In July 2007 a workshop was held entitled Management and Science of Fish Spawning Aggregations in the Great Barrier Reef Marine Park. The objective was to bring together an expert group including reef fish scientists, managers and fishers to discuss the current status of fish spawning aggregations in the Marine Park and prioritise management and science needs. The outputs of the workshop form a strategic direction for managing and researching Fish Spawning Aggregations in the Marine Park.

For further information on fish spawning aggregations, contact Martin Russell, Senior Project Manager, Fisheries Issues Group at m.russell@gbrmpa.gov.au