Faces of Sea Turtle Conservation: Dr. Larisa Avens, Research Biologist

June 06, 2018

A new technique developed by three NOAA Fisheries scientists is giving us more insight than ever before on sea turtle populations, extracting life history and other information from sea turtle bones. The technology combines bone dating, or “skeletochronology,” and the sequential sampling of annual growth rings in sea turtle bones to identify chemical signatures including stable carbon and nitrogen isotope ratios. Meet the scientists behind this new technology and how it is helping guide the way we protect and conserve sea turtles.

Dr. Larisa Avens with a loggerhead sea turtle.

Dr. Larisa Avens with a loggerhead sea turtle captured for tagging.

Dr. Larisa Avens has been a research fishery biologist with the Southeast Fisheries Science Center since 1998. She started her career with the sea turtle program at the Beaufort Lab, working with turtles in the water and doing behavioral research before shifting gears to focus on laboratory analysis. She has been the lead for skeletochronology research at the Beaufort Lab since 2003.

How did you first become involved in sea turtle research?

Growing up, I spent all my time outside catching reptiles and amphibians and bringing them home. I knew I wanted to be a biologist early on and once I discovered Archie Carr (the father of sea turtle conservation) and did more research on sea turtles and how much needed to be done for them, they became fascinating to me.

In 1998, I started with the sea turtle program at the Beaufort Lab, working with turtles in the water and doing behavioral research, and then shifted gears a little bit into the lab and analytical side of things.

What was your previous experience with bone dating (skeletochronology)?

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Photo: A dyed section of sea turtle humerus bone. Growth rings in sea turtle bones allow scientists to age the animal. By comparing growth rings with isotope concentrations, they are able to study diet and habitat shifts over the animals lifetime.
 

Aleta Hohn, my supervisor here at the Beaufort Lab, started using an analytical technique to analyze dolphin bones in the late 1970s and early 1980s. The sea turtle aging lab was established a few decades later in Beaufort, North Carolina, to take that analytical approach further. I took over the research in 2003.

Later I started working with Jeff Seminoff, and then Cali Turner, at the Southwest Fisheries Science Center to combine skeletochronology and sampling of annual growth rings for stable isotopes to find out how loggerheads were spending their time at sea.

Can you explain this new research and technique, combining bone dating (skeletochronology) and sampling of annual growth rings? What part did you play in it?

Thousands of turtles die and wash up (strand) along the coastline every year in the United States. We have a nationwide sea turtle stranding response and salvage network, and we put out requests to collect samples. Our partners—who are specially permitted—will salvage flippers from sea turtles for us. After we receive the sample, we remove the bones and use them for analysis. We use skeletochronology to look at the age and growth of different sea turtle species and to study growth patterns over the long term, for both individuals and populations.

We use a microscopic drill, similar to a dental drill, to drill out bone tissue from each individual growth mark. Our analysis estimates the age of the turtle and how quickly they had been growing. The stable isotopes tell us what habitat the turtle spent time in and what foods they ate, which can tell us whether they were in the open ocean or near shore, and when. It’s pretty remarkable that we can take this bone and get all this information from it—it’s almost like being a detective.

What does this research method reveal about sea turtle movement during the so-called “lost years”—when juveniles are growing and feeding in open ocean habitats?

After they hatch, sea turtle hatchlings crawl down the beach to the ocean and are carried by the currents out to sea. For several decades, the time from the emergence of hatchlings to the return of nesting females was called the “lost years.” This research helps us not only understand the lost years but also how feeding ecology might be changing as the turtles grow, and how their growth patterns might change. It also reveals how long these turtles are found in certain environments, which tells us how long and when they are exposed to location-specific threats. So far, we’ve only been able to look at a few different populations, but this unique method can be used to give us information on species around the world.

This type of research is also unique in its longevity. As long as we have specimens—even from decades ago—we can see how sea turtle feeding habits are changing compared to the present day, helping us determine what they need for food in a changing ocean. Strandings allow us to use these samples and this information to further our research and find out as much as we can about these sea turtles to better recover and protect them.

What is the biggest threat or concern for U.S. sea turtle populations right now? What can the public do to help protect them?

Sea turtles are exposed to many different threats throughout their lives. Bycatch in commercial fisheries is the most significant human-caused threat to sea turtles in the marine environment.  On the turtles’ nesting beaches, coastal development has reduced the amount of suitable nesting habitat. Lighting on beaches from roadways, dwellings, parking lots, and other development disorients hatchlings when they emerge from their nests, causing them to crawl toward the light rather than the water. Other important threats include vessel strikes and entanglement in marine debris.

To protect and conserve sea turtles:

  • Choose seafood caught in ways that do not harm sea turtles.
  • If you visit or live along the coast where sea turtles nest, turn off lights visible from the beach or use fixtures and lightbulbs designed to be “turtle friendly.”
  • Remove beach toys and beach furniture from the beach at the end of the day to avoid trapping or deterring nesting females or hatchlings.
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    Reduce the use of plastic—plastic balloons and plastic bags travel long distances and sea turtles may mistake them for food. Use reusable bags for shopping.  

What other sea turtle research are you working on right now and what new technologies are you excited about investigating in the future?

I’m excited about working with the Duke Marine Robotics and Remote Sensing Lab, who we collaborate with on how best to survey sea turtle populations at sea using specially permitted unmanned aerial vehicles (drones). Sea turtles are relatively small, don’t make noise, and can migrate long distances—so they are hard to find and track in the ocean. This is why it is important to use new technologies to expand our knowledge of them in their marine habitats.

Why is protecting and conserving sea turtles—the goal of this research—important?

Sea turtles are an integral part of the ecosystem, and without them things are going to get out of balance. When I first got into this research I came into it as a starry-eyed graduate student. I worked day in and day out with pound net fishermen for a decade to get live turtles and samples for research, and it helped me get a better perspective and different opinions on the aquatic environment. So I appreciate the challenges of conservation now. Sea turtles are remarkable animals, and their loss would be a huge loss to humans, too.

Last updated by Office of Communications on August 20, 2018

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