Gray's Reef National Marine Sanctuary
Gray's Reef National Marine Sanctuary
Data Buoy Science

Acoustic Tagging Project

Visitor Detections

VEMCO telemetry equipment is used by scientists around the world. Numerous researchers are using the technology up and down the eastern seaboard of the United States. Because VEMCO receivers can detect any VEMCO transmitters, scientists may find detections from unknown transmitters when they examine their own data. To determine the origin of detections from unknown transmitters, researchers have collaborated to establish networks to share transmitter ID codes with others. If researchers are unable to identify a transmitter using researcher networks, data can be submitted to VEMCO, who can identify whether the unknown detections are valid and identify the researcher who purchased the transmitter. This collaboration can be extremely valuable and result in details about fish movement that would have remained hidden were it not for the universal language of VEMCO equipment.

The identification of detections from unknown transmitters in Gray's Reef National Marine Sanctuary has resulted in the confirmation of several previously unrecorded species. None of the species below had ever been reported in Gray's Reef National Marine Sanctuary prior to being detected by VEMCO telemetry equipment:

Atlantic sturgeon (Acipenser oxyrinchus)

Atlantic Sturgen

Atlantic Sturgeon
(Photo: NOAA Fisheries)

Atlantic sturgeon can grow to 14 feet long and weigh up to 800 pounds. They are also slow-growing, late-maturing (5-34 years old for age at first reproduction), long-lived (can live up to 60 years), estuary-dependent fish that live the majority of their lives in saltwater, but hatch and spawn in freshwater. Atlantic sturgeon are easily recognizable by the 5 rows of prominent scutes or horny plates that run the length of their bodies. A protrusible, inferior mouth on the bottom of their head is used to locate food on the river, estuary, or ocean floor. There are thought to be 7-10 populations of Atlantic sturgeon along the east coast of the United States. Due to their historical overharvest and continually low population numbers, four Atlantic sturgeon populations were recently listed as Endangered under the Endangered Species Act in 2012.

Nine Atlantic sturgeon have been detected by acoustic receivers deployed at Gray's Reef National Marine Sanctuary. Some have been recorded passing through the sanctuary over multiple years. The sturgeon count now includes one fish that was originally tagged in the New York Bight by Dr. Keith Dunton with Stony Brook University, three tagged in Delaware by Dr. Dewayne Fox with Delaware State University, four were tagged in Edisto, S.C. by Bill Post with South Carolina Department of Natural Resources, and one was tagged in the Altamaha River by Dr. Daniel Erickson with UGA/UMiami. Sturgeon detections were recorded in late fall, winter, and early spring.

Great white shark (Carcharodon carcharias)

Great white shark

Great White Shark
(Photo: ARKive; Andy Murch,

Great white sharks are also large animals. A consensus has not been reached on a maximum size but it has been estimated to be about 6 m (19 ft) and maximum weights are estimated at 3,000 kg (6,600 lbs). Research suggests that they reach maturity between 9-14 years of age with a maximum reported age of 36. Their gray and white, spindle-shaped bodies are characterized by a blunt, conical snout and many rows of saw-edged teeth. This species is known for its long trans-oceanic migrations. Three populations of great white sharks are thought to exist, two in the Pacific and one in the Atlantic. Under the International Union for Conservation of Nature (IUCN) lists great white sharks as vulnerable, suggesting they are at a higher risk of global extinction than some other species.

One great white shark has been recorded on the acoustic receivers of Gray's Reef. The detections were logged at multiple receiver sites during one day in the spring of 2011 and spanned less than an hour, suggesting the animal was simply passing through the area. The shark was tagged by Dr. Greg Skomal with the Massachusetts Marine Fisheries off the coast of Cape Cod, MA and was measured to be about 4 m (13 ft) when tagged.

Bull shark (Carcharhinus leucas)

Bull shark

Bull Shark
(Photo: Bimini Biological Field Station)

The bull shark is another large predator and can reach up to 3.4 m (11 ft). The maximum reported age is 32 and they reach maturity between 10-15 years old. These sharks are viviparous, meaning they give live birth and litters tend to have around 13 pups. They have been known to inhabit rivers, estuaries, and coastal habitats with the ability to tolerate both salt and freshwater. The snout of the bull shark is very short and round with small eyes. Their bottom teeth are quite pointy, while the top teeth are more triangular and serrated. The IUCN lists bull sharks as near threatened.

Nine bull sharks have been detected in the telemetry array at Gray's Reef. All nine were tagged by Dr. Steven Kessel with the Bimini Biological Field Station and tagging took place near Jupiter, FL. Most of the bull sharks detected in Gray's Reef were females and some of them were detected in the sanctuary over multiple years.

Lemon shark (Negaprion brevirostris)

Lemon shark

Lemon Shark
(Photo: ARKive; Andy Murch,

The lemon shark can also reach sizes of 3.4 m (11 ft). Their maximum recorded weight is 187 kg (412 lbs) and maximum reported age is 25 years old. They too have a short snout but are identifiable by the yellowish overtone of their skin and a fairly large second dorsal fin that is near as large as the first dorsal fin. Lemon sharks are also viviparous and can have litters with 4-17 pups. The lemon shark frequents estuaries and the outskirts of mangroves as well as other more tropical coastal environments. They are also classified as near threatened under the IUCN Red List.

One lemon shark was recorded in the sanctuary that was also tagged by Dr. Steven Kessel of the Bimini Biological Field Station near Jupiter, FL. It was only detected in the sanctuary for a day in the summer of 2010 before departing the GRNMS array.


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