Terra-Tiger

If you’ve visited the GSTC recently, you may have had the opportunity to meet two of our newer patients: Terra-Tiger and Helio-Noel. Both of these juvenile green sea turtles came to the center in December after getting caught in dredging equipment off the coast of Jacksonville, Florida.  The more I talked about these two patients to guests, the more I realized that I knew very little about dredges and even less about their impacts on sea turtles. I did a little research on the topic and thought I would share my findings with GSTC blog followers who, like myself, might be interested in learning more about dredging and sea turtle safety.

To begin, a dredge is a machine that removes material from the sea floor. There are a couple of different types of dredges, and each is designed to accomplish a different task. Terra-Tiger and Helio-Noel encountered the dredge MV Terrapin Island, a trailing suction hopper dredge. This dredge type drags a suction apparatus that acts like a vacuum to pull up material from the seabed. Since sea turtles spend a lot of their time resting or foraging on the ocean floor, they are fairly vulnerable to being pulled into hopper dredge devices.

Dredges can do a wide variety of things, and in fact provide many services that are critical to the operation of other industries. They are perhaps best known for carving out the channels used by shipping and recreational vessels, however dredges can also be used for fishing, mining, beach renourishment, and pollution clean-up.

In the United States, dredging projects are managed and regulated by the US Army Corps of Engineers (USACE).  In order to minimize the negative impacts dredging may have on sea turtles, USACE has undertaken multiple studies to assess the consequences of dredging.  These have ranged from collecting abundance data in areas slated for dredging activity to testing methods that disperse or remove turtles before dredging projects begin. All of these efforts have resulted in USACE developing a series of protocols and equipment designed to lessen the threats that dredges pose to sea turtles.  Some of the practices developed to protect turtles from incidental take include:

• Restricting dredging activities to certain environmental windows: sea turtles aren’t typically found in water colder than 12 °C (about 54°F), so dredging projects often take place during the colder months of the year (December-March).

• Using exclusion equipment to prevent sea turtles from getting caught in dredges: the proper use of deflectors on dredging equipment has been shown to drastically reduce sea turtle entrapment.

• Dispersing or relocating sea turtles prior to dredging:  a variety of methods have been employed to remove turtles from dredge sites, including the use of trawl nets to capture and relocate turtles inhabiting the dredge pathway. Not all methods of dispersal have been found to be particularly effective, and many may not be used due to the high financial costs they entail.

• Implementing a monitoring program to keep track of incidental take of sea turtles: many dredging vessels are required to have a National Marine Fisheries Service-approved monitor on-board to examine dredge equipment and dredged materials for entrapped sea turtles. This is how Terra-Tiger and Helio-Noel were found and brought to the GSTC.

After getting pulled through a dredge, turtles may have a variety of injuries. Terra-Tiger arrived with internal bruising, some carapace abrasions and a fracture, as well as swelling in the eyes and neck. The turtle was also pretty lethargic and in shock, which is not surprising considering the extent of its injuries. As treatment, Terra-Tiger received fluid therapy for hydration and wound cleaning and debridement. Terra-Tiger continues to receive iron supplements to help combat anemia, as well as a variety of oral medications to head off infection.

Helio-Noel

Helio-Noel came to the GSTC about 10 days after Terra-Tiger and also had a serious array of injuries. These included multiple fractures to the carapace and plastron, as well as skin and shell abrasions.  In addition to cleaning and debridement, Helio-Noel’s early treatment involved the use of a WoundVAC, a device which uses negative pressure to create an environment that promotes wound healing.  These tough turtles still have a long road to release, but have many well-wishers rooting for their speedy recovery; several employees from the MV Terrapin Island have either called or stopped by the center to check up on their turtle friends!

There is a lot more information about dredging and sea turtles available online, and if you’re interested in learning more I encourage you to check out the following resources:

USACE Sea Turtle Data Warehouse:  http://el.erdc.usace.army.mil/seaturtles/

Historical review of dredging impacts and sea turtle protection: http://el.erdc.usace.army.mil/seaturtles/docs/2004WODCON-Dickerson.pdf

Presentation about the impacts of dredging on sea turtles: http://water.epa.gov/type/oceb/oceandumping/dredgedmaterial/upload/2009_08_27_oceans_ndt_about_15_get-science-right-dickerson.pdf

Sadie Mills

GSTC AmeriCorps Education Member