Species’ foraging choices influence their somatic growth rates, age at maturity, and time spent in vulnerable early life stages. Thus, differences in population demographics are often attributed to variability either in diet type, quality, and/or quantity ingested. Knowledge of diet selection, though currently limited, can enhance our understanding of the roles of marine turtles in marine ecosystems and, at a finer scale, elucidate how nutrition and diet influence their growth and productivity. To investigate this relationship, we coupled stable isotope analysis with a diet preference index to provide insights into the selection and plasticity of juvenile green turtle Chelonia mydas diet. The study was conducted at 2 sites (Bonefish Hole and South Bimini) in Bimini, Bahamas, in 2016. Habitat surveys were conducted to gather habitat data and determine resource availability. A dichotomy in diet was found between the sites: at Bonefish Hole, turtles exhibited a more generalist omnivorous diet, selecting for sessile filter feeders and green algae, whereas turtles in South Bimini had a more specialist herbivorous diet, primarily consuming seagrasses and selecting for red algae, when available. The foraging dichotomy found in this study expands our understanding of the spatial differences in green turtle biology in the Bahamas and provides novel information for turtle foraging in Bimini. Knowledge about differences in intra-specific diet, with a focus on diet selection and potential drivers, can shed light on the factors that influence critical life history traits and ultimately inform species management.

​Gillis, A. J., Ceriani, S. A., Seminoff, J. A., Fuentes, M. M. P. B. (2018). Foraging ecology and diet selection of juvenile green turtles in the Bahamas: insights from stable isotope analysis and prey mapping. Marine Ecology Progress Series, 599, 225-

 This summer marks the 3rd field season for Ph.D. candidate Matt Ware at the Bon Secour National Wildlife Refuge in Fort Morgan, Alabama working alongside the U.S. Fish and Wildlife Service and Share the Beach, an all-volunteer sea turtle conservation group. It has been a quiet year so far – only 30 nests, when in the last 2 years there have been 94 and 86 nests, respectively. Hatching has started with hatchlings from the only Kemp’s ridley nest on the refuge emerging on Monday 16 July. During the excavation, 108 eggs were found with 87 hatchlings successfully reaching the water. The first loggerhead nest should be hatching any day now.

His research this time around focuses on 1) studying the inundation tolerance of developing sea turtle embryos, and 2) the effect of Leave No Trace ordinances on nesting success. In past years, Matt has investigated the changes in incubation conditions associated with nest relocation and mapping wave runup exposure to identify high-risk nesting locations. To better inform these management strategies and tools, more information is needed on how well developing sea turtle embryos “hold their breath”. How long can embryos remain underwater and still hatch successfully? How does this tolerance vary with the timing of inundation relative to embryonic development and the frequency of inundation? Matt is using HOBO U20L-04 water level loggers to answer these questions, including 2 loggers donated by Onset Computer Corporation. Tropical Storm Alberto arrived in the northern Gulf of Mexico very early in the nesting season, so only 2 nests were affected. The peak of hurricane season is still to come in August and September – and the loggers are ready and waiting. This project has been funded by a Section 6 grant from the Alabama Department of Conservation and Natural Resources.

The second component of his research this summer constitutes the final year of data collection on a multi-year project tracking the nesting success across Baldwin County, Alabama. In 2015, the cities of Gulf Shores and Orange Beach enacted Leave No Trace ordinances. The “Leave Only Footprints” program as it is called forces beachgoers to remove their equipment from the beach no later than 1 hour after sunset or face civil penalties. This program does not apply to unincorporated Fort Morgan, and the 2 local protected areas – the Bon Secour NWR and Gulf State Park – already have their own versions of the Leave No Trace ordinance. By comparing nesting data before and after the enactment of the “Leave Only Footprints” program and within each year across the county, Matt will be able to assess if the program has improved nesting success, or at least decreased the frequency of obstructed crawls, in Gulf Shores and Orange Beach.
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Unfortunately, on Saturday 14 July, the need for such ordinances was demonstrated when a mature female Kemp’s ridley was found washed up during morning nesting patrol on the Bon Secour NWR apparently strangled by a beach chair. Matt assisted the Alabama Sea Turtle Stranding and Salvage Network in documenting the event and collecting the animal for later necropsy at the NOAA facility in Pascagoula, Mississippi. Images he captured of the turtle quickly went viral on social media and various news outlets. Posts on Matt’s personal Facebook page and the pages of Fort Morgan Share the Beach and the Bon Secour NWR have been viewed over 600,000 times and shared almost 9,000 times with almost 5,000 reactions. Now this’ story on the incident has been viewed 1 million times and shared over 12,000 times. The story was covered in the:

• NBC15, USA
• New York Times, USA
• Daily Mail, UK 
• Global News, Canada
• Huffington Post, South Africa
• Australia

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 Share the Beach has reached out to the Baldwin and Mobile County commissioners along with the governor of Alabama to urge them to support an expansion of the “Leave Only Footprints” program beyond the city limits. They, and Matt, hope that the images, though graphic, will encourage beachgoers to remove equipment from the beach at the end of the day, discard of damaged equipment properly, and help combat marine debris to prevent future impacts to wildlife.

When not in the field, Matt has been working on several manuscripts detailing his previous research in Alabama. Be on the look-out for his nest relocation manuscript currently in press in Chelonian Conservation and Biology and future manuscript on wave runup mapping.

Check out our new paper on the impacts of recreational scallop fisheries on marine turtles:

The impact of fisheries on marine megafauna is widely known but most studies have focused on commercial fisheries, overlooking the effect of local recreational fisheries. This is particularly important for marine turtles in near-shore habitats that overlap with recreational fisheries. We assessed the effect of recreational scallop fisheries on the distribution and behaviour of foraging marine turtles in the coastal waters of the upper Eastern Gulf of Mexico. Before and during the scallop season we quantified the density and overlap of marine turtles and vessels sighted, and satellite tracked four turtles to assess their distribution and behaviour. The relative distribution of marine turtles sighted during the scallop season overlapped with 48% of the area most frequently used by harvesters, and marine turtle activity hotspots shifted between seasons. In addition, during the scallop season the home range size of individual turtles appeared to decrease, and turtles displayed frequent changes in travel speed and directionality. We hypothesize that such changes are probably related to the distribution and movement of vessels and the abundant presence of people in the water. Our study highlights the importance of considering recreational fisheries and their local effect on marine megafauna for informing future adaptive management practices. However, further studies are needed to quantify the direct and indirect impacts of recreational fisheries and to assess the degree of risk of associated activities to marine turtle populations.

Reference:
Wildermann, N. Sasso, C., Gredzens, C., Fuentes, M. M. P. B. (2018). Assessing the effect of recreational scallop harvest on the distribution and behavior of foraging  marine turtles. Oryx