Acoustic Tagging Tog - The Fisherman

Acoustic Tagging Tog

A typical blackfish that is tagged with an acoustic tag.

Did you know about the acoustic tagging program for tautog off the South Shore?

Imagine being able to track movements of black sea bass and tautog, day or night, as they swim amongst an artificial reef, knowing exactly where and at what depth would be best to find a bite. As a Ph.D. student at Stony Brook University, I’ve spent the past four years working off the South Shore of Long Island, studying the movement and habitat use of local fish species.  Being that I don’t have a fishing background, I have been fortunate enough to work closely with some amazing anglers who have shared their expertise with me to further my research. It has been through this work that I’ve gotten to experience, firsthand, how much fun spending a day on the water fishing for blackfish and sea bass can be.  I have also seen how my research can help protect some of Long Island’s staple fisheries.

An E-ZPass for fish

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Since we can’t track animals underwater the same way we would use a GPS collar to track a dog, we use acoustic telemetry. Acoustic telemetry is a technology that is used to study the behavior and movement of fish by attaching a small electronic device that emits an acoustic signal.  Receivers placed in the water detect the signal, enabling researchers to track the fish over time.  Think of acoustic telemetry as an E-ZPass system for fish, similar to what we use on toll roads.  Just like an E-ZPass on a car can be detected by a sensor at toll booths, an acoustic tag on a fish can be “heard” by a receiver that has been placed in the ocean by a researcher.  Each time a tag is heard, it will record an electronic timestamp of when the fish swam by.

Our first step in the research process is setting up an array of receivers.  Each receiver collects and stores data, including the date, time, temperature, and unique fish identification.  For our artificial reef research, we deploy the receivers with SCUBA divers, who attach them directly to the reef structure or within the structure using an anchor. If you visited the Shinnecock artificial reef and dove down to a large tugboat, you’d find a small cylindrical device resembling a large black flashlight.  The top of the receiver has a dome-shaped hydrophone antenna, which detects the acoustic signals emitted from the tags.  A signal will only be recorded if a fish swims inside the range of the receiver.  The arrangement and location of receivers hold significant power in the information we can obtain.  Receivers spaced far apart can provide information about when the fish arrives at a site and how long it spends there. Every six months, we return to swap the receivers’ batteries and offload the data via Bluetooth. Once our receivers are positioned, it is then time to tag fish.

Each fish caught is measured and weighted.

Aquiring Test Subjects

Just like other anglers out at the reef, hook-and-line is the method we use for obtaining specimens for this project. Drifting has proven to be an effective method for catching fish across the entire reef area.  When we catch a fish, it is reeled in slowly to avoid barotrauma which can be caused by retrieving it from depth.  Once on board, we use an anesthetic to minimize stress and discomfort.  Each fish is measured and weighed to ensure it can handle the weight of the tag, which is designed to weigh less than a nickel and does not impact the fish’s behavior.  Next, we make a small incision in the body cavity into which we insert the acoustic tag. The incision is closed with surgical stitches. The fish is then tagged with an external conventional tag that contains contact information in case an angler catches the fish after we release it.  If you encounter one in good condition, please consider releasing it to help us collect this valuable data. After a brief recovery period, the fish is released back into the water.  A successful deployment is indicated when the fish is capable of swimming back down to depth on its own.

To date, we’ve tagged 20 tautog and 20 black sea bass at the Shinnecock artificial reef and the Shinnecock Mile Marker Buoy.  This represents a fraction of the over 200 fish we’ve tagged across the South Shore of Long Island.  Other species we have tagged include striped bass, fluke, weakfish, clearnose skate, winter skate, smooth dogfish, dusky sharks, sand tiger sharks and sandbar sharks.  Our primary focus is to understand how these fish are utilizing the artificial reef system that the New York State Department of Environmental Conservation (NYSDEC) has been deploying since the early 1960s.

Divers go down to the reefs to set the receivers in place and working properly.

Reefs Explained

The South Shore of Long Island is home to ten artificial reefs, (all of which can be found on the NYSDEC’s artificial reef program website along with GPS locations).  Each site is host to anywhere from 3 to 25 receivers.  These reefs provide exciting new dive spots and create more sport fishing access on Long Island.  By placing hard materials in areas where natural hard bottom structure is lacking, artificial reefs create complex habitats, especially where sandy bottoms are the dominant habitat type.  The material used to create the Shinnecock reef includes concrete, vessels, drydocks, a lighthouse, armored personnel carriers, jetty stone, pieces of the Tappan Zee bridge, and steel railcars. Thirty-one pieces are spread over a 35-acre area that ranges in depth from 79 to 84 feet.  Artificial reefs enhance the environment and create a biologically diverse area. They provide a home for a range of marine organisms, including algae, mussels, barnacles, sponges, anemones, hydroids and temperate corals, as well as other encrusting organisms that cover the reef over time.  As organisms settle on the structure, they attract marine life such as black sea bass, blackfish, porgy, fluke, eels and lobster.  Fish are drawn to the reef and surrounding areas for the abundant food and shelter they provide.

Where It Began

Our project started in 2019 with a single receiver.  We have since expanded our study area by placing four receivers within the boundaries of the Shinnecock area to create a box.  Receivers have been strategically placed at different sites, including vessels, concrete, and multiple materials from the demolition of the Tappan Zee Bridge.  Diving to deploy our receivers has been the highlight of our study for me.  It provided me with a sense of the rich diversity and abundance of marine life that can be found in the area.  An old trawler, deployed in the late 90s, is particularly fishy. The dozens of small holes and a large empty hold serve as hiding places for blackfish and cod.  Its towering trawler arms provide relief for black sea bass and cunner to swim around, and large schools of porgies are often seen congregating on its bow.  The wreck is adorned with large white and pink anemones, adding a burst of color to the otherwise all-green seascape.  If you search carefully, you may even find a receiver nestled around the northern star coral.  If you are patient and lucky enough, you may see a small flashing LED light of a receiver, indicating a detection of a tagged animal.

Black sea bass also receive tags if they reach the right length and weight requirements.

Seeing Results

Although not all the fish we tagged remained within the detection range of our receivers, we were able to detect 18 of the 20 tautog that were tagged at the Shinnecock artificial reef.  These fish were tagged in December 2021, and the receivers were removed in October 2022, providing us with the first insights into tautog’s activities for a 10-month period.

The blackfish we tagged showed a strong preference for staying around the reef structure.  Here they most likely feed on various invertebrates such as barnacles, crustaceans, and mollusks, which are abundant on sunken vessels.  In December 2021, most tagged fish were detected, but two left the reef in January, possibly due to inshore-offshore migration triggered by a drop in water temperatures below 50 degrees. By tagging our fish as the temperature reached the threshold for offshore movement, we may have missed fish that had already left, targeting a subset that stays inshore. Three of the fish were detected until mid-April when they were removed directly from the middle of the array, likely due to getting caught.  During May, the spawning season for tautog, which coincides with the closed fishing season, four of the fish left and did not return.  It is possible they moved closer to the mouth of Shinnecock Bay or other estuaries to spawn. Seven of the tagged fish were still present around the reef when we offloaded the receivers this October.  We had a greater number of detections on larger vessels, rather than on smaller rubble piles, with the greatest number of detections on those that have been deployed in the past ten years.  Younger pieces support large populations of blue mussels, a staple of the tautog diet offshore.  If you’re targeting tautog, you may want to focus your efforts on large reef material.

An acoustic receiver pictured on the reef.

The Future of Tagging

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In the fall of 2022, we expanded our receiver array to cover the entirety of Shinnecock and Moriches Artificial Reefs. This expansion will create an overlap in our receiver detection ranges, enabling us to triangulate exact fish positions in the water column, allowing us to answer highly detailed questions about how tautog are spending their time at the reef, including their depth preferences during different activities like resting, foraging and transit.  Tautog have been under intense fishing pressure for the last two decades, resulting in a 60% decrease in recorded landings.  For a slow-growing species like tautog, which can live up to 34 years and are not sexually mature until the age of four, the information we gather about their preferences for structure type will help us create better artificial reefs in the future.  This will help bolster and protect fish populations that depend on these habitats.

Next time you’re out fishing and encounter an external yellow tag, please consider releasing the fish and contacting us to let us know when and where it was caught, along with the number found on the tag.  If you’re looking for dinner, at least remove that acoustic tag, as it doesn’t pair well with the tasty flavor of blackfish!


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