Who lives on the reef?

  • Fishes
  • Long-term
  • Current
  • Research

Understanding how reef fish communities interact with the reef habitat is important to help understand what they require from these habitats. We monitor the different species that make up the reef fish communities of D’Arros Island and St Joseph Atoll, recording the abundance and distribution of species at different reef sites as well as the different size classes among the individuals of those species. Our staff usually take several weeks to collect this data annually.

Project details

Reef fish survey

Key objective

The key objective of the project is to monitor trends in reef fish diversity, abundance, size class and biomass across the reef sites of D’Arros and St Joseph.

Why is this important

Coral reefs support an incredible diversity of marine fish species. However, the health of these reefs continues to decline as a result of a variety of disturbances. While research into the status of the reef structures themselves is critical, far less is known about the consequences to the fish communities that depend upon them.


Coral-associated fish communities are made up a large variety of species. These species interact with coral reefs in different ways, with varying degrees of specialisation, habitat use and reliance on the reef itself. Changes in coral reef structure and complexity can affect predator–prey relationships and the availability of food, and thus the composition and stability of reef fish communities as a whole. Not only are reef structures important habitats for fish communities, but those communities themselves are important for the functioning of the reef ecosystem through the transfer of energy, the removal of sediment and grazing. Long-term monitoring of the abundance and diversity of reef fish communities can tell us about the susceptibility of different species groups to changes in reef condition, as well as the role they might play in facilitating the recovery of coral reef ecosystems.

Aims & objectives

The key objective of this project is met by several specific study objectives:

  • To survey the different reef fish species occurring at different sites around the islands;
  • To monitor long-term changes in the distribution and abundance of reef fish species;
  • To classify species by size class.