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Fine-scale foraging segregation in a green turtle (Chelonia mydas) feeding ground in the Bijagós archipelago, Guinea Bissau
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Advisor(s)
Abstract(s)
Green turtles (Chelonia mydas) are highly dependent on neritic foraging areas
throughout much of their life. Still, knowledge of recruitment dynamics,
foraging habits, and habitat use in these areas is limited. Here, we evaluated
how the distribution and food preferences of green sea turtles from different
life stages varied within a foraging aggregation. We focused on two islands in
Guinea-Bissau, Unhocomo and Unhocomozinho, using water captures and
survey dives to record habitat use and characteristics, and stable isotopes to
infer diet. Additionally, we used stable isotopes to infer their diet. Two habitat
types were sampled: deeper (2.26 ± 0.4 m) rocky sites fringed by mangrove
with macroalgae, and sandy shallows (1.37 ± 0.12 m) surrounded by rocky reefs
with macroalgae and seagrass. The two benthic communities were similar
isotopically and in terms of species composition, except for the presence or
absence of seagrass, which had unique signatures. We captured 89 turtles
ranging from 35 cm to 97 cm in curved carapace length (i.e., juvenile to adult
stages). Size distribution was habitat-dependent, with most smaller turtles
present in sandy shallows and larger turtles favoring slightly deeper rocky
sites. Turtle isotopic signatures differed between the habitat of capture,
regardless of size, revealing a marked dichotomy in foraging preference. All
turtles fed primarily on macroalgae, mostly rhodophytes. However, individuals
captured in sandy habitats had evident seagrass skewed isotopic signatures.
Larger turtles may be unable to use the more diverse shallower foraging sites
due to increased vulnerability to predation. Despite the proximity of the
sampled foraging sites (2.7 km apart), the two foraging subgroups seem to
maintain consistently different feeding habits. Our study highlights how
heterogeneous green turtle foraging habits can be within populations, even at
small geographic scales.
Description
Keywords
Chelonia mydas (green turtle) Foraging segregation Stable isotopes Dietary studies Bijago´ s archipelago Macrophytes
Citation
Madeira, F. M.,Rebelo, R., Catry, P. , Neiva, J., Barbosa, C. Regalla, A. & Patrício, A. R. (2022). Fine-scale foraging segregation in a green turtle (Chelonia mydas) feeding ground in the Bijagós archipelago, Guinea Bissau. Frontiers in Marine Science, 9. https://doi.org/10.3389/fmars.2022.984219
Publisher
Frontiers Media S.A.