Sea Turtles: Pilot Study Hopes to Help Reduce Bycatch

Written by on November 2, 2009 in Marine Life, Technology
Green Sea Turtle - NOAA's Coral Kingdom Collection - Photographer: Dr. Dwayne Meadows, NOAA/NMFS/OPR

Green Sea Turtle - NOAA's Coral Kingdom Collection - Photographer: Dr. Dwayne Meadows, NOAA/NMFS/OPR

Researchers are using modern technology to learn more about turtle behavior in commercial fishing areas and to develop new ways to avoid catching turtles in fishing gear, namely a remotely operated vehicle (ROV) and satellite-linked data loggers. 

Two juvenile loggerhead turtles were captured off New Jersey and equipped with satellite-linked data loggers that continually record water temperature, depth, location and time of day, have now been followed since August 24.

The turtles are currently about 30 miles off North Carolina.  The instruments log and store data, and should stay affixed to the turtles for at least six months and could remain attached as long as 18 months or more.  Data are relayed back to the lab via satellite when the animals are at the ocean’s surface.

The two turtles were in the northern part of a controlled access scallop fishing area known as Elephant Trunk.  Since being tagged, the turtles have been located in water depths between 165 and 230 feet (50-70 meters) and in water temperatures between 50 degrees Fahrenheit on the bottom to 72 degrees Fahrenheit on the surface (10 C – 22 C).  Temperatures are important because turtles get “cold-stunned” if the waters get too cold and can become stranded, a common occurrence on Cape Cod in the fall.

Loggerhead Sea Turtle - Courtesy of Anand

Loggerhead Sea Turtle - Courtesy of Anand

Heather Haas, Henry Milliken, Eric Matzen and Kimberly Murray of NOAA’s Northeast Fisheries Science Center (NEFSC) all work in the Woods Hole Fisheries lab’s Protected Species Branch, which studies marine mammals, sea turtles and sea birds.  Loggerhead turtles, the most common sea turtle in U.S. coastal waters, are currently a threatened species under the Endangered Species Act.  All sea turtle species are either threatened or endangered.

Other non-tagged loggerhead turtles have been followed with remotely operated vehicles (ROVs).  This is the first time an ROV has been used to follow turtles in the wild to learn about their behavior and how they interact with their habitat.

Ron Smolowitz of Coonamessett Farm in East Falmouth, Mass., says the F/V Kathy Anne, a commercial scallop vessel from Barnegat Light, N.J., on board which scientist spent three days in August, is ideal for the turtle research studies because the vessel has a crow’s nest atop the mast, making it easier to see turtles in the water.  Approximately 50 turtles have been located and followed with the ROV.  Researchers pay special attention to their behavior, including observing their feeding, swimming, how they interact with the ocean bottom and with each other.

He has worked with the NEFSC group since 2002 trying to learn more about sea turtles and has now been contracted by NEFSC to develop technologies to reduce the numbers of turtles caught in scallop dredges, such as excluder devices and modified dredges that deflect turtles away from the dredge opening.

Loggerhead sea turtle - Credit: Mito Paz/Marine Photobank

Loggerhead sea turtle - Credit: Mito Paz/Marine Photobank

Sea turtles spend most of their time submerged but rise to the surface to breath regularly.  During their waking activities turtle submerge for four to five minutes and surface to breath for one to three seconds.  When they rest or sleep they can stay submerged for several hours at a time.  Their ability to hold their breath is considerably shortened when they have heightened activity or are under stress, which is why they drown in nets or fishing gear in a short time.  Bycatch however accounts for more sea turtle deaths than any other source.  Therefore, decreasing the loss of turtles to commercial fishing is among the highest priorities on the list of conservation goals.

Henry Milliken said:

“The commercial scallop industry understands the importance of this research and has been very supportive of our efforts to understand and reduce turtle bycatch.  There is still a lot to learn about turtle behavior.  Knowing more would improve our ability to reduce bycatch and estimate turtle distribution and abundance.  The tags and the ROV images will provide some insights, but are only the start.”

Heather Hass said:

“I view this pilot project as a chance to work out the kinks for a larger, more comprehensive effort to study turtle behavior in commercial fishing grounds.  We timed this study to coincide with scallop fishing activity, and we are already gaining new and unique information on turtle behavioral patterns in the wild.”

The current project is being funded by NOAA Fisheries Service and the Atlantic sea scallop fishing industry.

Green Sea Turtle - Credit: Roy Niswanger/Marine Photobank

Green Sea Turtle - Credit: Roy Niswanger/Marine Photobank

Copyright ©  2009 by Marine Science Today, a publication of OceanLines LLC

About the Author

About the Author: Celia is Director of Business Operations for OceanLines LLC and is a frequent contributor to both OceanLines and Marine Science Today. She is a certified diver and her favorite topic is marine biology, especially stories about whales. .

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