Listening for the Fish

Researchers use high-tech acoustics to make marine-protected areas better

Rosenstiel School fisheries researchers will embark on state-of-the-art research at the end of February to track black and red grouper in the Dry Tortugas National Park to develop a better understanding of species’ movement and habitat require-ments, so they can help more efficiently design and assess future marine-protected areas. Through funding from the National Park Service and transportation support from Yankee Fleet Ferry Service, scientists will be able to conduct this high-tech observation that involves surgically implanted transmitters for approximately a year.

The scientists have designed a field study that uses acoustic telemetry technology to track continuously the movements and habitat use of red and black grouper in the Dry Tortugas National Park, the 46-square-nautical-mile marine reserve. The groupers will be fitted with transmitters or “pingers” that emit unique acoustic codes underwater approximately every 20 seconds. Passive listening stations or receivers will be placed in a submersed array that can detect the transmitters. Receivers will record an acoustic tag’s presence when it is within range, usually 250-1,000 meters, depending on the oceanographic conditions. And, because the tags each emit unique identification numbers and time stamps, individual receivers could potentially detect up to 4,000 different fish at any given time.

A red grouper pauses on the seabed of Dry Tortugas National Park, Florida, surrounded by gorgonian soft coral, sponges, and algae. (Photo by Rosenstiel School Associate Scientist Jiangang Luo.

The scientists are arranging the hydrophone receivers in a grid array, so they can systematically obtain continuous, precise tracks of animal locations, including daily travels and frequently visited areas.

“This study will generate a very valuable set of information,” said Dr. Jerry Ault, professor of marine biology and fisheries at the Rosenstiel School. “If we know how much and what kind of space is needed for these fish — some of the largest species in the ecosystem – then we can build a better marine reserve. And, that’s exactly what we hope to learn from this research about these grouper we want to protect. If we can get a sense of just how much space they need to have protected, so that they can swim, feed, and multiply freely, we can effectively rebuild their populations as well as the others that make up the coral reef ecosystem.“

In August 2005, the Florida governor and cabinet unanimously approved to implement a management plan for a no-take marine reserve in the Dry Tortugas National Park. The Florida Fish and Wildlife Conservation Commission concurred in early February 2006 with the proposed National Park Service regulations related to marine fishing in the park. The park’s marine reserve, coupled with that in the Florida Keys National Marine Sanctuary, is designed to protect precious coral reefs, fishery, and cultural resources, and to ensure sustainability of intensely exploited regional reef fisheries resources – benefiting the Tortugas, the Florida Keys and beyond.

Rosenstiel School is part of the University of Miami and, since its founding in the 1940s, has grown into one of the world’s premier marine and atmospheric research institutions.