Baby, It’s Cold in the Water

Early last year, Conservancy of Southwest Florida was contacted by Cody Mott with Inwater Research Group regarding techniques used to capture marine turtles in Southwest Florida waters. Inwater Research Group was assistingAdam Kennedy, director of the New England Aquarium’s SeaTurtle Hospital, with developing methods to catch and release turtles in Cape Cod Bay, Massachusetts as part of the Aquarium’s research program to learn more about turtles living in this temperate embayment. The method of rapidly deploying (or “striking”) a net from a boat has been used for scientific studies of marine turtles in Florida’s subtropical estuarine waters and wassuggested as compatible with the conditions found in Cape Cod Bay.  

Immature marine turtles, such as the critically endangered Kemp’s ridley, occur in Cape Cod Bay duringsummer months.Turtles that are unable to migrate southwardwhen water temperatures quickly drop in the fallbecome immobilized and wash up along the shoreline.The body temperature of these marine reptiles is regulated by the surroundingwater and they become lethargic (i.e., cold-stunned) when temperatures fall below a critical level, like iguanas and other tropical lizards that “rain” from trees when temperatures dip to near-freezing in Southern Florida.  

The New England Aquarium is part of a network of organizations that rescue and rehabilitate cold-stunned marine turtles that wash up along the Massachusetts coast every year. The number of cold-stunned turtles recovered inthis region has been increasing over the past 20 years, a possible sign of changing climatic conditions as turtles shift northward inwarming southern waters.In 2024, the New England Aquarium Sea Turtle Hospital treated over500 cold-stunned turtles, most of which were Kemp’s ridley turtles.  

Other than data collected fromcold-stunned recoveries, little is known about turtles inhabiting the temperate waters of Cape Cod Bay. In 1987, a Kemp’s ridley that had washed ashore the year before was instrumented withradio and acoustic transmitters to learn more about its movements and activities before the onset of the subsequentwinter. The turtle resided in specific areasamong the harbors and shoals along the eastern shore of the Bay before weather conditions halted the tracking. Nonetheless, theseefforts offered some of the first indications of how free-ranging turtles use Cape Cod Bay.More recently, in 2021 and 2022, researchers from the New England Aquarium implanted acoustic transmitters inrehabilitated loggerheadsand, each season,they attached satellite transmitters toseveral of these turtles based on sizeto investigate their survival and subsequent movement patterns after reintroduction to the wild. 

The New England Aquarium is developing a research plan forstudying marine turtles residing inthe waters of Cape Cod Bay to provide more information ontheir use of this ecologically important embayment. Aquarium staff have been talking to local people who regularly work on the water (fellow researchers, recreational and commercial fishers, ecotour operators, etc.) to gather locations of marine turtle sightings and identify potential areas where turtles aggregate. 

 The next step will be finding the right method to catch and releaseturtlesto collect scientific data such as species composition, population structure and seasonal occurrence of the Bay’s inhabitants.A number of techniques have been developed but the “tangle” nets commonly used forstudying in-water aggregations of turtles in Florida may be the most suitable given the prevailing conditions in the Bay (water clarity, depth, bottom type, tidal flow, etc.). 

To that end, Kristen Luise and Alexis Wrate with the New England Aquariumvisited south Florida in October 2024 for demonstrations of some of themarine turtle netting techniques used in our more tropical waters.The large-mesh nets used by researchers are eitheranchored in place for several hours (set netting), waiting for the turtle to swim into the webbing, or the nets are quickly deployed to encircle a turtle (strike netting)and retrieved immediately after the turtle becomes enmeshed in the net.  

The Aquarium staff first accompanied Inwater Research Group at their St. Lucie nuclear power plant project site on the southeast coast of the state. Seawateris used as a coolant for the power plant and marine animals, such as turtles, become entrained in the large diameter pipes that extend intotheAtlantic Ocean. Marine turtles are unable to escape from the intake canalto the power plant and are typically captured with set nets for removal from the canal. This presents a unique opportunity to collect scientific data on turtles inhabiting nearshore waters along Florida’s Atlantic coast before they are released back into the ocean. 

On the second leg of their journey, New England Aquarium staff Kristen and Alexis traveled to Southwest Floridafor a demonstration of the strike nettingmethod.This active form of turtle catch and release was first used to characterize the aggregation of marine turtles inhabiting the Ten Thousand Islands region and later employed for similar studies in the Charlotte Harbor estuary.Through a collaborative venture with Pat O’Donnell, fisheries biologist at Rookery Bay National Estuarine Research Reserve, a demonstration of this technique was arranged in the upper Ten Thousand Islands.Former and more recentin-water turtle research efforts have identified this estuarine archipelago of mangrove islands as important feeding grounds for Kemp’s ridleys and other species of marine turtles, much like that planned for Cape Cod Bay. 

Weather is one of the major factors when conducting in-water studies of marine turtles, affecting both the ability of researchers to capture turtles and the occurrence of turtles in coastal waters. Strong Easterly winds prevailed during the strike netting demonstration,owing to a low-pressuresystem in the Caribbean that would eventually spawn Hurricane Rafael, and these conditions limited our fishing efforts to the protected embayments among the mangrove islands. 

Furthermore, no turtles were sighted in thesebackwaters during our endeavor,which could have been a function of the three tropical cyclones (Debby, Helene, and Milton) that impacted our coastal areas earlier in the year. This region experienced “Irmageddon” in 2017 and turtles were scarceafter the hurricane owing todrastic changes to the benthic habitats (plants and animals living on the seafloor) in which they feed.Nonetheless, a tremendous amount of information wasrelayed among the participantsduring their time on the water and a dry run of strike netting was performed to give hands-on experience with handling the net. Hopefully, the knowledge gained during these demonstrations will help in the development of an in-water research program for marine turtles in Cape Cod Bay.  

Marine turtle research activities and photos by the Conservancy of Southwest Florida were conducted under National Marine Fisheries Service permit 22123 and Florida Fish and Wildlife Conservation Commission permit MTP-136, and those by the New England Aquarium were conducted under United States Fish and Wildlife Service permit ES69328D.