Isolated offshore reef habitats

From vast coral gardens to complex macroalgae beds, reef lagoons in the Coral Sea Marine Park are home to rich biodiversity. Many of these habitats may serve as fish nurseries, supporting young fish during the vulnerable early stages of life before they move elsewhere as adults.

These reefs are scattered across the nearly one million square kilometres of the marine park. Little is currently known about how fish use habitats in the marine park and potential connectivity between these isolated reef refuges.

We are building on our previous work mapping benthic habitats to investigate how fish communities use habitats in the Coral Sea Marine Park and how reef systems may be connected for fish populations. Results will guide conservation zoning and protection strategies for the marine park.

Surveying fish of the Coral Sea Marine Park

We are surveying fish species and their distribution across habitats in the reef lagoons of the Coral Sea Marine Park to identify fish nurseries and find patterns of diversity and connectivity across reefs.

We are using:

• Baited Remote Underwater Video Stations (BRUVS) to record fish species richness, abundance, and size across shallow to deep waters.

• Larval light traps to collect fish larvae and zooplankton, providing a measure of biological productivity.

• Otolith and genetic analysis for blue-spot coral trout (Plectropomus laevis) to determine whether individuals move between reef systems throughout their life.

Early results

Our initial surveys found:

• A wide range of juvenile and adult fish species.

• Different zooplankton species and biomass between deep and shallow water sites.

• A high number of juvenile sharks in reef lagoons.

Many fish species were gravid (carrying eggs) ahead of breeding; further monitoring is needed to identify the timing of breeding seasons and locate breeding grounds for these species.

These findings are contributing to baseline assessments of habitats, species diversity, and population connectivity to inform ongoing monitoring and long-term conservation of marine life in the Coral Sea Marine Park.

Project details

This project is led by Dr Samantha Tol and Dr Tim Smith and funded by Parks Australia and the Department of Climate Change, Energy, the Environment and Water.