Scientists track prehistoric fish with 21st century satellites

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Researchers release a tagged lake sturgeon into the Niagara River. Image: Shedd Aquarium/U.S. Fish and Wildlife Service

By Carin Tunney

Scientists are using marine-animal monitoring technology and satellites to reduce human threats to Great Lakes sturgeon.

Researchers  from the Shedd Aquarium and the  U.S. Fish and Wildlife Service studied lake sturgeon (Acipenser fulvescens) in the upper and lower Niagara River, which runs between Lake Erie and Lake Ontario.

Because lake sturgeon often reach 7 feet long and more than 200 pounds, they used the same technology ocean researchers use to collect habitat information on dolphins, sharks and turtles. It’s the first time Great Lakes fish were studied using the technology known as pop-off satellite tags, said Andy Kough, a marine ecologist with the Shedd Aquarium in Chicago.

The tags are attached with heavy-duty line, similar to fishing line, that is inserted into the fish’s back. The 15-inch tag is then hooked to a swivel on the end of the line, where it floats freely, inches above the animal’s back. The size of sturgeon make them good candidates for the technique.

“If you’re attaching a satellite tag, you have to make sure that it’s not going to interfere with the animal at all,” Kough said. “So we knew that it wouldn’t interfere with lake sturgeon, but it might if we were to put it on a little bass or something like that.”

It’s not necessarily an easy task to tag the fish.

Lake sturgeon are usually docile, but their behavior can change with the weather, said Fish and Wildlife Service biologist Dimitry Gorsky, who was part of the field research team.

“When the temperatures get a little bit warmer they tend to get a little more ornery, and you can get tail whipped pretty bad. It hurts pretty good,” he said. “If they want to flail around we let them do it, and then when they stop, we will go back to working on them, because they’ll always win if you are going to wrestle with them. They’ll always win.”

A researcher holds a pop-off satellite tag. Image: Shedd Aquarium/U.S. Fish and Wildlife Service

The satellite tags send summary information on the fish’s behavior to satellites. The tags eventually “pop-off” of the fish and float to the surface. They send a signal so scientists can retrieve them to learn more specific information.  Other researchers implanted the fish with microchips, similar to those used on pets, to gather long-term location information.

The 25 sturgeon that the researchers monitored were most active between sunset and sunrise.

“The information that we were able to collect was not so much on where the animals are, but when they are active, what time during the day, and more specifically, what time during the night that these animals were swimming more actively, and also at what depth they are swimming and what temperatures they are swimming in,” Kough said.

Gorsky said that information could help protect fish in Great Lakes shipping areas such as the St. Lawrence River and St. Clair-Detroit River system, where ships may kill lake sturgeon.

“Those two river systems are interesting because they have commercial shipping traffic,” Gorsky said. “We haven’t seen a lot of information in the Great Lakes about ship strikes with sturgeon, but it has been talked about with the Atlantic sturgeon in some of the coastal rivers, so it’s certainly something that we would be concerned about and wanting to make sure that it isn’t an issue.”

Lake sturgeon are making a comeback throughout the Great Lakes region. Image: Shedd Aquarium/U.S. Fish and Wildlife Service

Limiting the depth of overnight freighter movement by controlling weight load may be one way to prevent collisions between freighters and fish, researchers said.

Threats to sturgeon are a significant concern. They have lived in the Great Lakes for millions of years, according to fossil records. But the prehistoric-looking fish is now considered endangered or threatened throughout the Great Lakes basin because of overfishing in the early 1900s. Commercial fishing in Lake Erie removed millions of pounds of lake sturgeon a year, Gorsky said. Dam building also had a negative impact.

The number of lake sturgeon is increasing, said Phil Willink, a senior research biologist with the Shedd Aquarium.

“If we had tried to do this project 20 years ago, we probably wouldn’t have caught enough to do the project, so it is interesting that they are making a comeback in that harbor,” he said. “That’s a good sign.”

Future research involves acoustic monitoring, which uses hydrophones to track fish movements and locate spawning areas, the researchers said.

“The more data we get, the more comprehensive view we have of their life history and that puts us in a better position to protect them, and there’s still a lot to learn,” Willink said.

The study is published in the Journal of Great Lakes Research.

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