19 Jun
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Listening for Fish: Acoustic Array in RI Waters

Part of the acoustic array off Block Island. Photo courtesy of Atlantic Shark Institute .

The waters off Rhode Island have been a black hole when it comes to knowing the habits and migrations of many fish species. True, some fish carry acoustic tags that produce a signal which could relay an abundance of information. Trouble was, there was nothing around here to listen to that signal.

That began to change recently with the deployment of an “acoustic array”, a dozen listening devices designed to pick up those signals. DEM’s Conor McManus, Deputy Chief of Marine Fisheries and Jon Dodd, Chairman of the Atlantic Shark Institute (ASI), placed the receivers and will share information about the endangered Atlantic Sturgeon as well as the many shark species around Rhode Island.

“There has been a gap in coverage for many years,” said McManus. “There are acoustic arrays off the Massachusetts and Long Island coasts, but none off Rhode Island. This project allows us to bridge that gap. We can get an idea of which fish not only move through our waters but stop in Narragansett Bay. The array will tell us when the sturgeon come, when they leave, and which corridors they are using.”

Atlantic Sturgeon live in coastal waters along much of the east coast. They are anadromous, meaning that they hatch in fresh water, live most of their lives in salt, then return to fresh water to spawn. The bony plates running along the side of the fish, called scutes, give it a prehistoric look, and they may live to be 60 years old. At 14 feet in length and 800 pounds, these are impressive animals. Sturgeon are also the same animal from which caviar was obtained. It’s this latter quality that caused dramatic reductions in their population in the early 20th century. Since then, habitat degradation and accidental catching in fisheries (called bycatch) have landed it on the endangered list.

Hundreds of fish of different species have been tagged along the East Coast, but without acoustic receivers, there has been no way of knowing what happens to them as they move through Rhode Island. “We placed the arrays at the mouth of the East Passage, the West Passage, the Sakonnet River, and off Block Island,” said McManus. The array will remain in place until the fall, then pulled for the winter to prevent loss due to rougher winter waters. McManus is enthusiastic about the teaming of DEM with a rapidly growing nonprofit like the Atlantic Shark Institute.
“ASI has a specific interest in sharks up and down the east coast. They wanted to be a cornerstone for a new knowledge base about shark movement, behavior, and ecology for those in and around RI. The partnership is new, but we’ve been working collaboratively to place these monitors.”

Marker for an acoustic receiver. Photo courtesy Atlantic Shark Institute .

“Both DEM and ASI are interested in promoting shark science and proper management of sharks within Rhode Island waters. We’re interested in improving our knowledge base of the coastal pelagic creatures in state waters.”
Dodd is enthusiastic about his organization’s role in the growth of shark knowledge. “We are tremendously excited about this. We just got a message from a noted shark scientist who requested to be part of our advisory council. It’s those things that we’re excited about. We’re getting people who are well respected and are interested in collaborating with the ASI.” For Dodd, the next steps will likely involve ASI doing some of their own tagging, and possibly doing workups on the sharks to establish their health and habits.

It’s possible DEM will tag fish at a future date. For now, they will use some of the information gathered to determine the presence or absence of the sturgeon, and to attempt to understand where they enter Narragansett Bay. They will also investigate how well the method itself is working. For now, McManus is pleased with the start.

“I have a number of staff who worked really hard to apply for the grant (that paid for the equipment), and design the arrays. The array reflects the effort of many scientists working together to learn more about fish habitat and migration in Rhode Island.”

Learn more about the Atlantic Shark Institute at www.atlanticsharkinstitute.org.

Hugh Markey is a freelance writer, naturalist, and educator living in Richmond. Read more articles on his blog, “Science and Nature for a Pie”, and follow him on Facebook here .

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