Derby
Crew Member
Radio telemetry revealing secrets of aquatic species.
By Karl Blankenship, Editor
The Bay Journal
www.bayjournal.com
It took more than two years — and endless hours of frustration — before biologists found their first sturgeon on Marshyhope Creek.
DNR biologist Chuck Stence makes a small incision in the belly of a sturgeon last year on Marshyhope Creek. The lipstick-size acoustic transponder (in the hand of another biologist lower left) will be inserted into the fish, the incision sewn and the fish returned to the water. (Dave Harp)
Week after week, they went to the river and placed 100-yard gill nets, only to pull them out empty. Then, last fall they finally caught eight adult fish.
Now, they can find them any time they want. They just have to turn on their computer.
"They can't hide from us because we have tags in them," said Chuck Stence, a fisheries biologist with the Maryland Department of Natural Resources, referring to tiny electronic transmitters scientists had implanted in each fish.
About every 90 seconds, the transmitters send out a high-frequency signal that identifies the fish and its location. If there is a receiver nearby — roughly within a half-mile — it picks up and logs the information until biologists retrieve it and load it into their computers. Now, biologists know when the sturgeon are around and where they are hanging out. "We basically have the whole river wired now for sound," Stence said.
It's not the only wired place in the Bay. As the fish migrated out the Marshyhope and down the Chesapeake last fall, Stence was able to trace their movements along the Bay's deep channel until they exited at the south end of the Chesapeake Bay Bridge-Tunnel.
Throughout the Bay, and all along the East Coast, scientists are tagging thousands of fish while building a network of receivers that allows them to track their movements in a way unimaginable little more than a decade ago.
Scientists believe the information they are gathering will help them locate critical habitats, such as spawning grounds, while shedding new light on coastal migrations, where fish may be vulnerable to nets targeting other species. Such data could help protect rare or threatened species, such as sturgeon, while improving management for more common fish, such as striped bass.
For centuries, much of the lives of fish, especially those that migrate along the coast, was hidden under the waves. Most of what scientists knew about their movements came primarily from tagging and recapture programs, in which biologists placed external tags on fish and waited for the fish to be captured and the tags returned, usually by fishermen.
"Now, we are more or less letting the fish tell that story rather than the recapture of tagged fish in fisheries, which provide a biased account of where those fish go," said Dave Secor, a fisheries scientist with the University of Maryland Center for Environmental Science.
Secor has been placing high-frequency acoustic transmitters in striped bass captured in the Patuxent and Potomac rivers and tracking their movements through the Bay and along the coast. Mature female striped bass were thought to spawn annually, but Secor has found that some take a couple of years off between spawning runs — information that could never be gained from traditional tag and recapture programs.
Further, programs that hinge on recaptures don't work well for species that are rare, like sturgeon, and therefore unlikely to be caught again. "This lets us find needles in a haystack, where you have really big water like the Bay or tidal river, and relatively few needles," said Greg Garman, director of the Center for Environmental Studies at Virginia Commonwealth University.
Maryland DNR biologist Mike Porta retrieves an acoustical receiver from its underwater home at a dock on Marshyhope Creek. The receiver is used to get data from any fish that has been outfitted with a transmitter. (Dave Harp)
Biologists began using acoustic tags more than a decade ago. Initially, they had to chase the fish in boats until the scientists grew too exhausted to follow. But new transmitters with longer battery lives and longer ranges keep pinging out information about a fish for years. Scientists began placing receivers along the shoreline — even on buoys — which could pick up pings and store the data.
Instead of chasing fish on a boat, biologists could walk away for weeks, or months, then download data from the receivers and load it into a computer. They can plot the movements of dozens, even hundreds, of individual fish logged by the receiver.
Unexpected pings
Then, something else began to happen — individual scientists began getting pings from fish they didn't tag; they began encountering each others' fish as they swam by. Instead of just tracking fish in a local river, they could — by exchanging information — track longer migrations.
"If you put these receivers out, you have the potential to hear from thousands of tags, and that has actually been happening," said Dewayne Fox, a fisheries scientist with Delaware State University, and one of the first to use the acoustic technology.
After chatting with others at a fisheries meeting a decade ago, Fox led the establishment of the Atlantic Cooperative Telemetry Network, a collection of scientists who exchange data from fish tagged along the East Coast.
Altogether, roughly 100 scientists in the network have tagged nearly 10,000 individual fish over the last decade. They represent about 75 species, from alewife and striped bass to bluefin tuna and sand tiger sharks. "If you can think of something that swims in the ocean, chances are someone has put a tag on it," Fox said.
By Karl Blankenship, Editor
The Bay Journal
www.bayjournal.com
It took more than two years — and endless hours of frustration — before biologists found their first sturgeon on Marshyhope Creek.
DNR biologist Chuck Stence makes a small incision in the belly of a sturgeon last year on Marshyhope Creek. The lipstick-size acoustic transponder (in the hand of another biologist lower left) will be inserted into the fish, the incision sewn and the fish returned to the water. (Dave Harp)
Week after week, they went to the river and placed 100-yard gill nets, only to pull them out empty. Then, last fall they finally caught eight adult fish.
Now, they can find them any time they want. They just have to turn on their computer.
"They can't hide from us because we have tags in them," said Chuck Stence, a fisheries biologist with the Maryland Department of Natural Resources, referring to tiny electronic transmitters scientists had implanted in each fish.
About every 90 seconds, the transmitters send out a high-frequency signal that identifies the fish and its location. If there is a receiver nearby — roughly within a half-mile — it picks up and logs the information until biologists retrieve it and load it into their computers. Now, biologists know when the sturgeon are around and where they are hanging out. "We basically have the whole river wired now for sound," Stence said.
It's not the only wired place in the Bay. As the fish migrated out the Marshyhope and down the Chesapeake last fall, Stence was able to trace their movements along the Bay's deep channel until they exited at the south end of the Chesapeake Bay Bridge-Tunnel.
Throughout the Bay, and all along the East Coast, scientists are tagging thousands of fish while building a network of receivers that allows them to track their movements in a way unimaginable little more than a decade ago.
Scientists believe the information they are gathering will help them locate critical habitats, such as spawning grounds, while shedding new light on coastal migrations, where fish may be vulnerable to nets targeting other species. Such data could help protect rare or threatened species, such as sturgeon, while improving management for more common fish, such as striped bass.
For centuries, much of the lives of fish, especially those that migrate along the coast, was hidden under the waves. Most of what scientists knew about their movements came primarily from tagging and recapture programs, in which biologists placed external tags on fish and waited for the fish to be captured and the tags returned, usually by fishermen.
"Now, we are more or less letting the fish tell that story rather than the recapture of tagged fish in fisheries, which provide a biased account of where those fish go," said Dave Secor, a fisheries scientist with the University of Maryland Center for Environmental Science.
Secor has been placing high-frequency acoustic transmitters in striped bass captured in the Patuxent and Potomac rivers and tracking their movements through the Bay and along the coast. Mature female striped bass were thought to spawn annually, but Secor has found that some take a couple of years off between spawning runs — information that could never be gained from traditional tag and recapture programs.
Further, programs that hinge on recaptures don't work well for species that are rare, like sturgeon, and therefore unlikely to be caught again. "This lets us find needles in a haystack, where you have really big water like the Bay or tidal river, and relatively few needles," said Greg Garman, director of the Center for Environmental Studies at Virginia Commonwealth University.
Maryland DNR biologist Mike Porta retrieves an acoustical receiver from its underwater home at a dock on Marshyhope Creek. The receiver is used to get data from any fish that has been outfitted with a transmitter. (Dave Harp)
Biologists began using acoustic tags more than a decade ago. Initially, they had to chase the fish in boats until the scientists grew too exhausted to follow. But new transmitters with longer battery lives and longer ranges keep pinging out information about a fish for years. Scientists began placing receivers along the shoreline — even on buoys — which could pick up pings and store the data.
Instead of chasing fish on a boat, biologists could walk away for weeks, or months, then download data from the receivers and load it into a computer. They can plot the movements of dozens, even hundreds, of individual fish logged by the receiver.
Unexpected pings
Then, something else began to happen — individual scientists began getting pings from fish they didn't tag; they began encountering each others' fish as they swam by. Instead of just tracking fish in a local river, they could — by exchanging information — track longer migrations.
"If you put these receivers out, you have the potential to hear from thousands of tags, and that has actually been happening," said Dewayne Fox, a fisheries scientist with Delaware State University, and one of the first to use the acoustic technology.
After chatting with others at a fisheries meeting a decade ago, Fox led the establishment of the Atlantic Cooperative Telemetry Network, a collection of scientists who exchange data from fish tagged along the East Coast.
Altogether, roughly 100 scientists in the network have tagged nearly 10,000 individual fish over the last decade. They represent about 75 species, from alewife and striped bass to bluefin tuna and sand tiger sharks. "If you can think of something that swims in the ocean, chances are someone has put a tag on it," Fox said.
