Oysters, Red Drum, and
Toadfish (oh my!) at the Rachel Carson Reserve
In March, scientists from Maryland, Virginia, and North Carolina shared their research on fishery resources and aquatic
ecosystems at the American Fisheries Society - Tidewater Chapter conference held at the N.C. Aquarium at Pine Knoll
Shores. During the three-day conference, graduate students from East Carolina University, UNC-CH Institute of Marine
Sciences (UNC IMS), and other institutions featured research occurring in and around the Rachel Carson Reserve (RCR).
Studies included everything from the movement of larval oysters to the impacts of boat noise on oyster toadfish
reproduction. Reserve Communications Specialist, Emily Woodward, grabbed a front row seat during the presentations
and captured some of the exciting research taking place at RCR.
Oyster Restoration
It’s no secret that North Carolina’s oyster population has experienced significant decline as a result of habitat loss,
disease, overharvesting, and pollution. In an effort to reverse this trend, researchers in Dr. Joel Fodrie’s lab at UNC IMS
are exploring innovative ways to monitor larval oyster movement, restore reefs, and measure reef growth over time.
Graduate student Ian Kroll is studying the movement of larval oysters in
Pamlico, Core, and Back Sounds. Because oyster larvae (as well as many fish
and crustacean larvae) are microscopic in size, their movement is notoriously
difficult to track in nature. Ian is using a relatively novel approach to
overcome this obstacle by combining geochemistry and ecology. As oyster
larvae develop, their shells absorb trace elements present in the waters in
and around their birth place. Like a human fingerprint, the ‘elemental
fingerprint’ in the larval shell of oysters can be used to identify their birth
location. So, Ian set out to sample oyster spat, which are newly settled
Graduate student Ian Kroll works in the lab, Photo by
UNC IMS
oysters that have attached to a hard substrate, from various sites, including
the Rachel Carson Reserve, to collect the elemental fingerprint of individual spat. By knowing the location a spat settles
and using the elemental fingerprint of the shell to infer birth location, Ian is able to quantify movement patterns of
oyster larvae. Knowing where larvae move to and how far they’re moving will help focus future restoration efforts by
prioritizing the location and spacing of restoration efforts to maximize the exchange of larvae among oyster reefs.
Danielle Keller plants marsh grass, photo by UNC
IMS
Continuing with the restoration theme, graduate student Danielle Keller is
studying how salt marsh landscapes can affect the success of restored oyster
reefs and their ability to serve as habitat for fish and crustaceans. Landscape
types include marshes in tidal creeks, marshes that gradually slope from the
marsh edge to the sandy sea-bottom, and marshes that are highly eroded, which
is characterized by a drastic cliff-like edge into the water. To see which species
are using restored reefs, Keller and her lab mates sampled sites at the three
different landscapes and documented oyster density and the abundance and
types of marine life. Results at this study site suggest that oyster reefs located in
more protected areas, such as marsh creeks, are more successful in their
development than those located in more exposed landscapes; however, fish
showed no preference based on location.
Fishing for Answers
Little is known about the movement of red drum, North Carolina’s state
saltwater fish, so Fodrie lab graduate student Matt Kenworthy designed a
study aimed at gaining further insight into where these fish spend their
time. His project involved tagging juvenile red drum within Back Sound
and the North River Estuary by surgically implanting acoustic tags through
a small incision made on the underside of each fish. After the surgery, the
fish were released back into the areas from which they were sampled.
Tagged fish were monitored using underwater receiver stations, deployed
by researchers, that would pick up a “ping” from a tagged fish whenever it
Matt Kenworthy performs surgery on a red drum, photo by
would swim within range of one of the stations. This method allowed
UNC IMS
researchers to quantitatively model their movement over the course of a
couple of months. This model helps researchers understand red drum distribution and abundance, the mixing of
populations, and food web dynamics.
The slightly less popular oyster toadfish might not be as sought
after among fishermen as red drum, but it has proven to be
quite useful in understanding soundscape ecology in shallow
water estuaries. Underwater soundscape ecology involves
studying how sounds affect organisms in a particular
environment. Cecilia Krahforst, a graduate student in the
Coastal Resources Management Program at East Carolina
University under the direction of Dr. Joseph Luczkovich, is
investigating the impact of boat noise on oyster toadfish
communication, reproduction, and larval development, which
An oyster toadfish, photo by Mietta Morris
is funded by a National Science Foundation’s Doctoral
Dissertation Improvement Grant. Krahforst studied how the soundscape influences the communication rate of male
oyster toadfish that produce a “boop” sound to attract females to male dens. Results show that noise from boat motors
does cause a reduction in the number of “boops” produced by male toadfish and results in reduced mating success, as
measured by the number of embryos in a toadfish den. These results suggest that toadfish in areas exposed to repetitive
boat noise have reduced communication rates and reproductive output than toadfish in areas exposed to less boat
noise. These results are the first evidence that boat sounds are impacting fish reproduction and may be applicable to
other sound-producing species like red drum and spotted seatrout.
How do Scientific Studies help the Reserve?
Projects like these highlight the mutually beneficial relationship between the Reserve and the scientists that utilize the
Reserve’s 10 sites. These valuable partnerships support the Reserve’s research priorities of providing living laboratories
for scientists, conducting research that’s relevant to coastal management needs, and increasing basic understanding of
estuarine processes. Information obtained through these partnerships help the Reserve’s stewardship staff balance
visitor access and resource protection to conserve the roughly 42,000 acres of coastal and estuarine ecosystems that are
protected under the North Carolina Coastal Reserve and National Estuarine Research Reserve program.