Identification of the Gulf of Mexico as an important high‐use habitat for leatherback turtles from Central America

Abstract

Endangered leatherback sea turtles (Dermochelys coriacea) are wide‐ranging, long‐distance migrants whose movements are often associated with environmental cues. We examined the spatial distribution and habitat use for 33 satellite‐tracked leatherbacks from nesting beaches on the Caribbean coast of Costa Rica and Panama from 2004 to 2018, an important nesting population for the leatherback Northwest Atlantic Distinct Population Segment. Tracking revealed the use of two distinct regions, the Gulf of Mexico (GoM, n = 18) and the North Atlantic Ocean (NAO, n = 15). We developed density utilization maps to elucidate high‐use habitats, migration pathways, and seasonal movements. GoM leatherbacks were found in three concentrated high‐use habitats connected by a migration pathway, while NAO leatherbacks were primarily found in a single, large high‐use habitat. Leatherbacks in both regions have the potential to interact with Atlantic pelagic longline fisheries based on seasonal overlap with high fishing effort. Our findings suggest that the GoM is an important destination for leatherbacks from the Caribbean coast of Central America with seasonal movements between high‐use habitats within the GoM. While leatherbacks are utilizing high‐use habitats in both the NAO and the GoM, the proportion of individuals migrating into the GoM increased over the study period. Additionally, NAO leatherbacks have increased the distance they travel in the first 90 d. Regional differences in movement and spatial distribution of high‐use habitats are important considerations when developing conservation plans for the Northwest Atlantic leatherback population.

Genetic variation among sea turtle life stages and species suggests connectivity among ocean basins

“…The Gulf of Mexico is an important habitat for adult foraging leatherbacks from nesting beaches in Costa Rica and Panama (Evans et al, 2021 ); however, data are scarce for juvenile leatherbacks in the Gulf of Mexico, or any ocean basin, because of their exclusively offshore life history (Bolten, 2003 ). With similar sampling gaps for olive ridleys and flatbacks (Figure 3 ), collaboration with commercial and traditional fisheries (LaCasella et al, 2014 ; Lopez‐Mendilaharsu et al, 2019 ; Ng et al, 2014 ; Parker et al, 2005 , 2011 ; Stewart et al, 2019 ) and local non‐profit groups will facilitate sample collection.…”

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

“…The first one is that this probability shall be rather small, probably below 0.5, as at least half of the simulated juveniles cross the GoM too briefly to encounter favorable foraging zones. This partly explains why the fraction of adult WCA leatherbacks observed to migrate into the GoM (55% according to Evans et al, 2021) is well smaller than the fraction of WCA juveniles simulated to visit the GoM (96%).…”

“…The high use of the GoM by WCA leatherbacks is also confirmed by satellite tracking: out of 33 female leatherbacks tracked from WCA nesting beaches, 18 (55%) migrated, and foraged, into the GoM, while the others directed their post-nesting migrations toward the north Atlantic Ocean. Both Stewart et al (2016) and Evans et al (2021) questioned whether the high use of the GoM by WCA leatherbacks is linked to juvenile dispersal following the LMG hypothesis. Given our simulation results, one is tempted to immediately answer "yes" as the percentage of WCA juveniles visiting the GoM (96%) is much larger than in any other stock (Table 3).…”

“…Juveniles entering the Loop Current during intrusion events will obviously circulate further and longer into the GoM (Figure 8B). They will have opportunities to visit more productive areas found deeper in the northern part of the GoM, in the shelf waters of southwest Florida or in the Campeche Bay, where adult leatherbacks are observed to forage (Aleksa et al, 2018;Evans et al, 2021;Sasso et al, 2021). Some of them will also become trapped in eddies shed by the Loop Current.…”

“…Such comparisons however must be done with great care as juvenile dispersal is not the only factor influencing adult distribution. In this paper, we provide a mathematical formalization of the LMG hypothesis and use it to show that juvenile dispersal patterns simulated by STAMM can, to a large extent, explain a) why adults of the different NWA stocks are present in widely different proportions in the Gulf of Mexico (GoM) (Stewart et al, 2016) and b) why the fraction of adults migrating from the WCA nesting beaches into the GoM has been increasing during the last decade (Evans et al, 2021). The GoM is a region where the risk of interactions with human activities is especially high (e.g., Valverde and Holzwart, 2017).…”