Variation in Species Composition, Size and Fitness of Two Multi-Species Sea Turtle Assemblages Using Different Neritic Habitats

Abstract

The neritic environment is rich in resources and as such plays a crucial role as foraging habitat for multi-species marine assemblages, including sea turtles. However, this habitat also experiences a wide array of anthropogenic threats. To prioritize conservation funds, targeting areas that support multi-species assemblages is ideal. This is particularly important in the Gulf of Mexico where restoration actions are currently ongoing following the Deepwater Horizon oil spill. To better understand these areas in the Gulf of Mexico, we characterized two multi-species aggregations of sea turtles captured in different neritic habitats. We described species composition and size classes of turtles, and calculated body condition index for 642 individuals of three species captured from 2011 to 2019: 13.6% loggerheads (Caretta caretta), 44.9% Kemp’s ridleys (Lepidochelys kempii) and 41.4% green turtles (Chelonia mydas). Species composition differed between the two sites with more loggerheads captured in seagrass and a greater proportion of green turtles captured in sand bottom. Turtles in sand bottom were smaller and weighed less than those captured in seagrass. Although small and large turtles were captured at both sites, the proportions differed between sites. Body condition index of green turtles was lower in sand habitat than seagrass habitat; there was no difference for Kemp’s ridleys or loggerheads. In general, smaller green turtles had a higher body condition index than larger green turtles. We have identified another habitat type used by juvenile sea turtle species in the northern Gulf of Mexico. In addition, we highlight the importance of habitat selection by immature turtles recruiting from the oceanic to the neritic environment, particularly for green turtles.

Capture vulnerability of sea turtles on recreational fishing piers

“…However, this may simply reflect variation in body shape as Kemp’s ridley grow. Lamont and Johnson (2021) reported lower BCI values for Kemp’s ridleys >40 cm SCL at SRI as compared to those <40 cm SCL. Mean BCI of our pier‐caught turtles (1.39) was similar to mean BCI reported for 40–49 cm SCL Kemp’s ridleys by Lamont and Johnson (2021; 1.41).…”

“…Examining stable isotope values for net‐caught and pier‐caught turtles would help clarify the diet of these individuals, including whether pier‐caught turtles are only foraging on bait or also foraging on algae and epibionts growing on the pier structure (Vander Zanden et al, 2013). Our small numbers of recaptured turtles (particularly those with recapture intervals >180 days; Lamont & Johnson, 2021) prohibited us from comparing growth rates of pier‐caught and net‐caught turtles.…”

“…Kemp’s ridleys are commonly documented as incidental captures on fishing piers (Coleman et al, 2016; Cook et al, 2020; Seney, 2017); however, during our study, green turtles dominated pier captures. Species composition of pier captures most likely reflects the composition and abundance of species using surrounding waters; green turtles are frequently captured in nearshore waters off of northwest Florida (Lamont & Johnson, 2021). Additionally, although the genetic origin of juvenile green turtles captured on the pier is unknown, green turtle nesting has increased exponentially in Florida in recent years (Ceriani et al, 2019) while loggerhead nesting has remained stable (Ceriani et al, 2019) and Kemp’s ridley nesting appears to have declined (Caillouet et al, 2018; Gallaway et al, 2016).…”

Long‐term apparent survival of a cold‐stunned subpopulation of juvenile green turtles

“…Size at sexual maturity varies across regions with East Pacific green turtles maturing at smaller sizes than northwest Atlantic green turtles (Avens & Snover, 2013; Seminoff, Resendiz, Nichols, & Jones, 2002). Body size information indicates green turtles in St. Joseph Bay emigrate before reaching ~80 cm straight carapace length (Avens et al, 2012; Lamont & Johnson, 2021). St. Joseph Bay is highly susceptible to rapid water temperature declines due to its topography and location (Foley et al, 2007).…”

“…Juvenile green turtles exhibit strong site fidelity to neritic foraging areas in bays (e.g., Bass et al, 2006;Redfoot & Ehrhart, 2013;Shimada et al, 2014). Although studies are limited, satellite tracking , telemetry (Lamont et al, 2015), and tag recoveries (Lamont & Johnson, 2021) support this hypothesis of high fidelity of juvenile green turtles to St. Joseph Bay. All green turtle populations in the United States are federally listed, with Florida populations considered threatened (National Marine Fisheries Service & U.S.…”