Great white shark 'pings' trackers off Seacoast: Here's what that really means

Two weeks ago, the Boston newscasters were all excited about a great white shark that “pinged” off Rye Beach.

While having a great white in our waters does not surprise me as the commercial fishermen see them frequently, I was surprised that it had made it onto the Boston television stations. Curious, I delved deeper and soon found that the “ping” was 100 miles off the New Hampshire coast. While interesting, it seemed a little bit of sensationalism to report it off the coast of Rye Beach. So, I thought it would be a good time to discuss what a “ping” was.

I’ll start by explaining the different types of acoustic tags. Some types have been in use throughout the Gulf of Maine for decades. The first type is a pop-up tag. These tags have been used on fish, sharks, turtles and whales. They have helped us learn more about what depth the animals frequent and where they have been. These can determine migration patterns and mating behavior. They are affixed to the outside of the animal and collect data such as GPS positions, water depth and temperature, etc. They stay affixed on the animal until the unit pops off and floats to the surface. At that time, they transmit all their data to a satellite, which is then collected and sifted through by scientists.

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The second type of acoustic tag is a transmitter, which is attached to the animal and stays on for up to 10 years. Seasonally, receiver buoys are strategically placed in areas frequented by animals. When an animal with a transmitter swims near a buoy, the buoy’s receiver records which animal swam by it. The transmitters on the animals send a unique frequency for each animal. These buoys are usually removed from the water once a year. The receiver is sent to a laboratory where the information is downloaded. Scientists then sift through the data and determine which animals swam by and when. These types of acoustic tags are good for tracking migrations and give a little insight into water temperature at the buoy site.

The third type of acoustic buoy has a similar transmitter affixed to an animal, but the buoy and receiver are more complex. The buoy’s receiver is constantly transmitting to a satellite. When an animal swims within 300-400 feet of the buoy’s receiver, the satellite receives the information in real-time, and the scientists get a “ping” in real time on their computers. These types of acoustic buoys are very useful in tracking specific animals’ migration in real-time and can be insightful when studying shark behavior. They allow local authorities to know when sharks are in their vicinity. They can also be extremely useful in tracking the real-time movements of endangered animals, thus enabling fisheries managers to enact regulations that will protect them from human interaction in real-time.

Unfortunately, all these tags are extremely expensive. Keep in mind that a camera tag will cost up to $10,000 each, and pop-up tags run about $4,000 each and last for two years when the battery dies. The acoustic tag transmitters cost around $425 each, and the receivers and buoys run more than $2,500. All these tags can have issues that affect their usefulness, like causing injury to the animals while attaching the tags or loss of buoys due to storms or ship strikes. Scientists also must consider anomalies like tags that record animals going into extreme depths. This can occur if an animal is eaten by a predator or it dies from natural causes and sinks to the bottom.

Some acoustic tags have been paired with a tiny camera. That information can be transmitted to a satellite along with the GPS information, giving scientists the shark’s eye view of his prey and insight into how they hunt. In recent years, scientists have been able to miniaturize these tags to less than the size of an AA battery. The smallest tags are implanted just below the skin behind the fin by a harpoon. This is quite an improvement over the first tags, which were incredibly large and could change the natural behavior of an animal.

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Unfortunately, this information is limited by the number of individual animals that can be tagged. First, you need to find the animal, catch it, and place the tag on it. In addition, many of the pop-up tags are lost due to predation and natural mortality. The buoys are often lost due to storms and ship strikes. All these issues must be considered by the scientists when they publish the results of their studies.

The most important issue is the number of individuals that have been tagged. It is just a small fraction of the animals in any population. So, in the case of shark species, we must always remember that if there is one “ping,” there may be many more sharks swimming in your vicinity. If you are interested in following the “pings” along the East Coast, you can check out several apps in your app store.

As for the shark that pinged off New Hampshire, he was probably headed straight to feast on the seals in Nova Scotia after having munched on some seals off Cape Cod. The chance of a shark making a sharp left turn and heading 100 miles toward the New Hampshire coast is minuscule. Vigilance is always your best choice. And once again, I would emphasize, “If you see a seal in the water, GET OUT OF THE WATER,” or you may be a shark’s next appetizer.

Ellen Goethel is a marine biologist and the owner of Explore the Ocean World at 367 Ocean Blvd. at Hampton Beach.