Gray's Reef National Marine Sanctuary
Gray's Reef National Marine Sanctuary

Linking Prey Fish and Predators at Grays Reef:
Visual and Acoustic Surveys
Provide Complimentary Perspectives

Greater Amberjack attack juvenile tomtate at the seafloor.

Greater Amberjack attack juvenile tomtate at the seafloor in Gray's Reef National Marine Sanctuary.
Photo: Dr. Peter Auster (UConn/Mystic Aquarium)


Reefs, or undercut ledges, in Gray's Reef National Marine Sanctuary are the ecological stage where fish predators and their prey strongly interact. The results of research over the past seven years has shown that predators act in single and mixed species groups to enhance predation success, that predator and prey activity vary over the course of the day and from reef to reef, and that both predator and prey abundance at reefs also vary over space and time.

Dr. Fabio Campanella collects acoustic data of fish distribution.

Dr. Fabio Campanella (NOAA/NOS), working in the glow of computer monitors, collects acoustic data of fish distribution after sunset
Photo: Dr. Peter Auster (UConn/Mystic Aquarium)

Acoustic surveys to assess fish distribution and abundance at and around reefs from 2011-2013 have demonstrated that overall, prey fish have increased over time. However, direct underwater observations suggest a reverse trend when we only focus on reefs. This suggests that prey fish resources have moved away from reefs as their abundance increased, a density-dependent effect. Further, perhaps predators, at least those large enough to avoid becoming prey for most larger fish, follow the prey fish away from reefs.

Dr. Peter Auster and his team began the 2015 survey work on Monday, July 27 and have been conducting operations using the Gray's Reef research vessels. Weather and underwater visibility have been excellent all week, allowing the team to be productive all week. Surveys continue until August 4th. A few photos of the week's work are shown above.

Aggregation of great barracuda.

Aggregation of great barracuda (seen in background of photo) above a school of prey (tomtate).
Photo: Dr. Peter Auster (UConn/Mystic Aquarium)

This year we plan to address questions that have emerged from previous observations. That is: how do prey resources at reefs vary over the course of day-night periods and at different tidal stages, do aggregations of prey fish on and off reefs have a characteristic pattern in relation to density and school shape, do predators follow prey away from reefs and interact differently than on reefs? We will use acoustic and direct visual survey methods to assess spatial variation in distribution of prey and associated predators both on and off reefs over 24 hr periods to collect fine-scale data to answer these and related questions about the ecology of reef communities.

Screengrab of echogram showing large and discrete schools of fish.

Screengrab of echogram showing large and discrete schools of fish above a ledge. Top image depicts the entire water column, while the lower image is the shows only the near seafloor echos. Warmer colors indicate stronger echos and higher densities of fish.
Click image for larger view.
Photo: Dr. Fabio Campanella (NOAA/NOS).

Dr. Peter Auster is interviewed by Emily Jones of GPB News

Dr. Peter Auster is interviewed by Emily Jones of GPB News.
Click image to hear how he explained that a higher-powered version used by the researchers than that of the fish-finding technology you'll find on many fishing boats gives the researchers a broad picture.
Photo: Emily Pepin (Mystic Aquarium)

Dr. Peter Auster splashes to begin a research dive .

Dr. Peter Auster splashes to begin a research dive.
Photo: Emily Pepin (Mystic Aquarium)


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