Reef predators

Reef predators are declining around the world, with many populations exposed to overfishing. AIMS scientists are examining the movement patterns of reef-associated fish and sharks to define how they use these complex environments and how effective management and conservation efforts are.

We are investigating how fish and sharks move on reefs, how long they remain on a single reef, how often they move between reefs, how they respond to changes, such as temperature, in their environment and how far they travel.

Understanding movement patterns in reef environments will clarify how much protection is provided by closing zones to fishing. This information is particularly crucial for the management of sharks, which are highly mobile.

For example, if a fish spends most of its life on a reef closed to fishing then it will be well protected. If it moves between zones open and closed to fishing, the level of protection decreases.

AIMS uses underwater listening stations, or acoustic receivers, to study the movement of fish and sharks. These units are anchored around reefs and listen for the presence of fish fitted with transmitters.

Acoustic transmitters are surgically implanted into the abdomen of fish and sharks to ensure retention. Fish receive smaller transmitters that have a tracking duration of about 12 months. Sharks can carry much larger transmitters so they can be tracked for multiple years.

Tracking individuals over long periods tells us whether movements change with seasons or reproductive patterns.

Our study species include several that are popular with fishers such as coral trout and redthroat emperor. We are also studying a variety of sharks, both smaller, more reef-attached species such as grey and blacktip reef sharks, and larger, more wide-ranging species such as silvertip, tiger and bull sharks.