Gray's Reef National Marine Sanctuary
Gray's Reef National Marine Sanctuary
Gray's Reef Expedition 2012
Mission Information
 

Wednesday: May 23, 2012
Log Day 9

Noelle Hawthorne
GRNMS Graduate Intern / Savannah State University

Divers Kelly Gleason (l), Randy Rudd (c) and Sarah Fangman (r) prepare to deploy acoustic array

Divers Kelly Gleason (l), Randy Rudd (c) and Sarah Fangman (r) prepare to deploy acoustic array.
(Photo: Kacey Johnson)

We are finally back on the reef and getting down to business! The seas calmed down to 2-3 feet yesterday, allowing us to safely launch the boats and divers from the NOAA Ship Nancy Foster. The skies were clear and beautiful, a welcome omen to a productive day.

I was able to get out and enjoy the spectacular weather. I sat topside on a launch that was charged with working on setting up the VR2W Positioning System (VPS) in the sanctuary. A VR2W is a certain type of acoustic receiver that listens for the unique pings of individual transmitter and records the dates and times they are received. We have many of those placed throughout the sanctuary, but the VPS array is special. It includes six receivers spaced closely together surrounding a ledge and a reference tag in the middle of all the receivers. Since they are not far apart, when a tagged fish is in the area it will be picked up on more than one receiver. How often a fish is recorded on a receiver in a short period of time tells us how far away the fish is from the receiver. With this information from multiple receivers we can determine the exact location of a fish as long as it is inside or near the VPS array.

Noelle Hawthorne downloading data from acoustic reciver retrieved from Gray's Reef

Noelle Hawthorne downloading data from acoustic reciver retrieved from Gray's Reef.
(Photo: Debbie Meeks)

This information is difficult to get for marine animals. With terrestrial animals, we usually just observe them for a while and write down their habits. But when it comes to marine animals, in order to observe we have to be SCUBA diving. This can be expensive and require a lot of people because the air in your tank will only let you observe for so long. That's why acoustic telemetry is a great way to constantly monitor these fish and what they are doing without having to dive and observe them. The results we get from acoustic telemetry studies are important in how the fish are protected by managers.

Acoustic array anchors retrieved by the ship, and ready to redeploy in new locations

Acoustic array anchors retrieved by the ship, and ready to redeploy in new locations.
(Photo: Debbie Meeks)

The VPS array is a great way to study fish on a fine-scale while the other receivers throughout the sanctuary track the broader movements of the fish. For example, we can use the normal receivers in the sanctuary to tell how long the fish remain in the sanctuary, which usually occurs on the order of months. Conversely, the VPS array can tell us where the fish tend to be at night compared with during the day. We are very excited to start getting results from the VPS!

Tagged black sea bass, with yellow spaghetti tag visible near the dorsal fin, swims near ledge in Gray's Reef

Tagged black sea bass with yellow "spaghetti" tag visible near the dorsal fin, swims near ledge in Gray's Reef NMS.
(Photo: Randy Rudd)

Another triumph of the day was the tagging of two more gag grouper, one of which was quite large! That brings our total to 13 tagged fish with 7 more to go. I have a feeling that tomorrow will be another productive tagging day.

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