Mote scientists tag-and-release two spotted eagle rays off Longboat Key
On June 21, Mote scientists released two spotted eagle rays off Longboat Key after fitting them with acoustic tags in an effort to learn more about their life history, reproduction and population status in the first-ever comprehensive spotted eagle ray conservation project in the Gulf of Mexico.
Since the inception of this project in 2009, Mote scientists have learned that in the Sarasota area, there are all size classes of spotted eagle rays from babies (pups) to adults and that some rays either stay in the area or return after periods of months to years. Some pups are born in the late summer and early fall and the rays move or migrate to other locations in winter months when our local waters are too cold.
Mote scientists have also noted a declining then stabilizing trend in numbers of rays observed in aerial and boat surveys, which indicates a need for continued monitoring of this species’ status.
While spotted eagle rays are protected in Florida, they are not protected under federal laws and international protections are limited. These rays are harvested in Mexico and Cuba as food, and this fishing pressure, combined with their extremely low reproductive rate, makes them a vulnerable species.
Currently, there is not enough information about the distribution, migration, feeding habits, growth rates and reproductive biology of spotted eagle rays, which is why Mote researchers initiated a multi-collaborative conservation research project on this animal in 2009.
“With the help of many organizations from across the country, and even internationally, we have been able to start documenting information on the population status of spotted eagle rays in the Gulf of Mexico,” said Kim Bassos-Hull, Mote Marine Laboratory senior biologist. “This information is crucial, because spotted eagle rays are a good indicator of overall health of the ecosystem. Their primary diet is composed of mollusks (clams, oysters, snails etc.) and understanding how they impact this resource and their connection to other trophic levels such as predators is important for safeguarding the overall health of our oceans. Also, there are probable impacts from targeted fisheries in nearby countries such as Mexico and Cuba, where people consume spotted eagle rays, and understanding population structure is important to managing them in the region.”
To learn more about this species’ status in the Gulf of Mexico, biologists have sampled, tagged and released about 540 spotted eagle rays off Southwest Florida since 2009 through a multi-collaborative project with many organizations, including international ones in Cuba and Mexico, involved in the research.
Main collaborators are from Mote; California Academy of Sciences in San Francisco; El Colegio de la Frontera Sur (ECOSUR) in Campeche, Mexico; Georgia Aquarium in Atlanta; Harbor Branch/Florida Atlantic University in Ft. Pierce, Florida; University of Havana’s Center for Marine Research in Havana, Cuba; and University of South Florida Sarasota-Manatee.
“Spotted eagle rays are a protected species in the state of Florida. In order to conserve them we need to understand where they go and what they eat, and we can do this by using various techniques such as satellite and acoustic tagging, new technologies that were not available to researchers 20 years ago,” Bassos-Hull said.
On June 11, Mote scientists fitted two spotted eagle rays (one 57 pound male and one 77 pound female) with acoustic tags, which are small ultrasound-emitting devices that can emit signals for years. Underwater hydrophones pick up the tag’s signal when the ray swims by it, which allows researchers to learn about their behavior. These rays were released 10 days later to the area where they were found, off of Longboat Key.
“The data we hope to collect from these tags will give us a location and time for the rays’ presence in an area close to underwater receivers,” Bassos-Hull said. “We will download the data from the receivers once a month and check for our tagged rays. From these data we can learn about ray movement patterns both locally in our area and throughout the Gulf of Mexico as part of a larger array system.”
Mote’s Spotted Eagle Ray Conservation Research Program is also working in Mexico and Cuba to understand fisheries pressure in those countries and collect genetic samples for population analysis for the Gulf of Mexico and Caribbean region.
This conservation project began with support from the National Aquarium in Baltimore, but has since expanded into a full research program supported by several funding sources including the Disney Worldwide Conservation Fund, the Save Our Seas Foundation and the Georgia Aquarium.
Mercury Marine, which has been making world-class outboards and sterndrives for more than 75 years, is also a major supporter of this research project, as it donated a large portion of the cost of the engine to operate the Ono V boat Mote scientists use to conduct this research project.