Photo by Leif Johnson

Catch Me If You Can

By Conservancy Research Manager Dr. Jeff Schmid

Marine turtles spend most of their lives underwater, briefly surfacing every so often to catch a breath before returning to their cryptic habits. The estuarine waters in Southwest Florida are usually turbid (murky) which makes it difficult, if not impossible, to observe turtle behaviors underwater. For these reasons, we must perform “in-water” studies to capture marine turtles inhabiting our coastal waters and collect information that is vital to their conservation. Our research efforts focus on the Kemp’s ridley, considered the most endangered marine turtle species, and the estuaries of western Florida provide important feeding grounds for young turtles.

Conservancy’s research vessel for in-water marine turtle studies

We capture Kemp’s ridleys with tangle nets, as was done during the former turtle fishery in Florida, using a specially-designed research vessel known as a mullet skiff. The boat is driven to areas where turtles are known to occur and we wait to catch a glimpse of a ridley surfacing to breath. When a little white head is spotted, we rapidly deploy the net and try to encircle the turtle. We then wait for signs the turtle has hit the net and become entangled, at which point the net (and hopefully the turtle) are retrieved into the boat. Sometimes the turtle escapes our capture efforts and that is why it is called “turtle fishing” rather than “turtle catching”.

Video from Charlotte Harbor National Estuary by Nancy Fitzsimmons

On a recent trip in the Ten Thousand Islands, we had just finished capturing a Kemp’s ridley when another turtle surfaced off the bow. The net was deployed again and the turtle soon surfaced within the set. It appeared to be grasping something in its mouth that we later identified as a stone crab, a known food item in these waters. Typically, a turtle will entangle within 15–20 minutes but this particular ridley was in no hurry to get caught. Every several minutes, the turtle surfaced with its crab in the middle of the encircling net and it continued taunting us for 40 minutes. These observations of a ridley at the surface handling its prey were unique given that these turtles spend approximately 95% of their time under the murky waters, presumably feeding on the bottom.

Photo by Leif Johnson

The Kemp’s ridley finally finished its lunch and promptly became entangled. Upon boating this turtle, we noticed monofilament fishing line trailing from its mouth. Kemp’s ridleys are known bait stealers and some may become habituated to the “free meals” at fishing piers. A foot or so of fishing line was pulled from the turtle until resistance was met. Not wishing to cause damage from a potential hook in the esophagus or stomach, the line was cut at the turtle’s mouth. Closer examination revealed the trailing portion of monofilament had been cutting into the edge of the turtle’s mouth, a sign that the fishing line had been consumed some time ago. We headed back to the Rookery Bay National Estuarine Research Reserve field station to place the ridleys in plastic tubs filled with seawater as part of our ongoing diet studies.

While temporarily holding the turtles, we contacted Florida Fish and Wildlife Conservation Commission (FWC) to locate a facility that could check for fish hook ingestion. The next day the turtle was transported to the Clinic for the Rehabilitation of Wildlife (CROW). A radiograph (x-ray) of the turtle did not reveal any ingested fish hooks and it eventually passed fishing line along with crab parts. The rehabilitated ridley was released on the backside of Sanibel Island, across from a former in-water study site for marine turtles in the Charlotte Harbor National Estuary. Our research has shown that Kemp’s ridleys are faithful to specific feeding grounds. Releasing this turtle in a different feeding ground is essentially a displacement experiment to test for site fidelity. Flipper tags and a microchip were applied to the turtle and we hope to recapture this elusive ridley down in the Ten Thousand Islands during future turtle fishing trips.

If you find a dead, sick, or injured sea turtle, please call FWC’s 24-hour Wildlife Alert Number at 1–888–404-FWCC (1–888–404–3922). Be prepared to answer questions on the location, whether the turtle is alive or dead, the approximate size, whether the turtle is marked with spray paint (i.e., previously documented), and the closest access point. If the turtle is alive, please be prepared to stay with it until help arrives.

Our research activities are conducted under NMFS permit #13544 and FFWCC permit #136. Our studies are funded in part by grants awarded from the Sea Turtle Grants Program which is supported by proceeds from the sale of the Florida Sea Turtle License Plate. Learn more at www.helpingseaturtle.org.