Dispersal of juvenile leatherback turtles from different Caribbean nesting beaches: A model study

Abstract

The Northwest Atlantic (NWA) leatherback turtle (Dermochelys coriacea) subpopulation was recently classified as endangered. It nests in the Wider Caribbean Region and includes five genetic stocks, all declining, albeit at different rates. The causes of decline are multiple and difficult to identify based on annual nest counts which integrate the effects of multiple stressors over the entire life history. Demographic models, however, show that survival during the juvenile pelagic stage is the main factor modulating population trends, but this life stage remains largely unobserved. This paper presents a suite of numerical simulations where juveniles from the five NWA stocks disperse under the combined effects of ocean currents and habitat-driven swimming movements. Simulations reveal when and where NWA juveniles likely disperse and, thus, the environmental conditions and anthropogenic threats they may encounter. Simulated individuals initially disperse following either the “Caribbean route,” inside the Caribbean Sea and the Gulf of Mexico (GoM), or the “Atlantic route” east of the Antilles Islands Arc. The percentage of individuals following one or the other route varies markedly with the stock of origin. Late dispersal in the eastern Atlantic Ocean and the Mediterranean Sea is similar in all stocks. Juveniles following the Caribbean route are rapidly entrained northwards by the Gulf Stream and incur a high risk of cold-induced mortality. This mostly affects the Florida stock and the Western Caribbean (WCA) stock nesting in Costa Rica, Panama, and Colombia. The Atlantic route is less lethal as individuals progress more slowly toward higher latitudes. Simulations also show that the percentage of WCA juveniles visiting the GoM is larger than for any other stock. The learned migration goal (LMG) hypothesis, which posits that adult sea turtles tend to exploit foraging areas previously identified at the juvenile stage, may thus explain why WCA adults are overrepresented in the GoM. Finally, our results suggest that the recently observed increase in the percentage of WCA adults migrating into the GoM could be linked to bycatch reduction measures implemented in 2003–2004, combined with an increase in the frequency of Loop Current intrusion and eddy-shedding events that started around the year 2000.

Biogeography of Greater Antillean freshwater fishes, with a review of competing hypotheses

“…One possibility is that Puerto Rico is relatively remote from other bioregions except NSA and is isolated from that bioregion by the Caribbean Current, which flows westward, away from Puerto Rico. The one species inhabiting Puerto Rico, K. hermaphroditus, also inhabits the Lesser Antilles (Berbel-Filho et al, 2022), suggesting it dispersed along the Antillean Current from north-eastern South America, a pattern seen in juvenile sea turtles (Gaspar et al, 2022), but not in other freshwater fishes.…”

“…This directed outflow from the Gulf of México to the Straits of Florida (Guertin, Missimer & McNeill, 2000) and, combined with narrowing of the Central American seaway [Late Oligocene (Montes et al ., 2012; McGirr, Seton & Williams, 2021)], to establish the Caribbean–Loop Current System (Hübscher et al ., 2023). This system served as a dispersal avenue from northern South America to the Bahamas, with Central America, North America, and Cuba as points in between (Gaspar, Candela & Shillinger, 2022). Also in the Oligocene, uplift of the Andes Mountains created a continental, subAndean river system that discharged into the Caribbean from north‐western South America (Hoorn et al ., 2010; Wesselingh & Hoorn, 2011).…”

Biogeography of Greater Antillean freshwater fishes, with a review of competing hypotheses

“…This directed outflow from the Gulf of México to the Straits of Florida (Guertin, Missimer, & McNeill, 2000) and, combined with narrowing of the Central American seaway (Late Oligocene, Montes et al, 2012; McGirr, Seton, & Williams, 2021), to establish the Caribbean-Loop Current system (Hübscher et al, 2023). This system serves as a dispersal avenue from northern South America to the Bahamas, with Central America, North America, and Cuba as points in between (Gaspar et al, 2022). Also in the Oligocene, uplift of the Andes Mountains created a continental, subandean river system that discharged into the Caribbean from north-western South America (Hoorn et al, 2010; Wesselingh & Hoorn, 2011).…”

“…Island immigration is dated 0.5-0.1 Ma (Tatarenkov et al, 2017). This species has a unique distribution pattern including the Lesser Antilles and Puerto Rico (Berbel-Filho et al, 2022), suggesting dispersal via the Antilles Current, as observed in juvenile leatherback turtles Dermochelys coriacea (Gaspar, Candela, & Shillinger, 2022). However, a population of K. hermaphroditus in EP-CB bioregions indicates the species also either dispersed via the Caribbean Current to the Panamá-Columbia Gyre or along the northern coast of South America.…”

“…One possibility is that Puerto Rico is relatively remote from other bioregions except NSA and is isolated from that bioregion by the Caribbean Current, which flows westward, away from Puerto Rico. The one species inhabiting Puerto Rico, K. hermaphroditus , also inhabits the Lesser Antilles (Berbel-Filho et al, 2022), suggesting it dispersed along the Antillean Current from north-eastern South America, a pattern seen in juvenile sea turtles (Gaspar et al, 2022), but not other freshwater fishes.…”