J. M. Blumenthal

Turtle groups or turtle soup: dispersal patterns of hawksbill turtles in the Caribbean.

Despite intense interest in conservation of marine turtles, spatial ecology during the oceanic juvenile phase remains relatively unknown. Here, we used mixed stock analysis and examination of oceanic drift to elucidate movements of hawksbill turtles (Eretmochelys imbricata) and address management implications within the Caribbean. Among samples collected from 92 neritic juvenile hawksbills in the Cayman Islands we detected 11 mtDNA control region haplotypes. To estimate contributions to the aggregation, we performed ‘many‐to‐many’ mixed stock analysis, incorporating published hawksbill genetic and population data. The Cayman Islands aggregation represents a diverse mixed stock: potentially contributing source rookeries spanned the Caribbean basin, delineating a scale of recruitment of 200–2500 km. As hawksbills undergo an extended phase of oceanic dispersal, ocean currents may drive patterns of genetic diversity observed on foraging aggregations. Therefore, using high‐resolution Aviso ocean current data, we modelled movement of particles representing passively drifting oceanic juvenile hawksbills. Putative distribution patterns varied markedly by origin: particles from many rookeries were broadly distributed across the region, while others would appear to become entrained in local gyres. Overall, we detected a significant correlation between genetic profiles of foraging aggregations and patterns of particle distribution produced by a hatchling drift model (Mantel test, r = 0.77, P < 0.001; linear regression, r = 0.83, P < 0.001). Our results indicate that although there is a high degree of mixing across the Caribbean (a ‘turtle soup’), current patterns play a substantial role in determining genetic structure of foraging aggregations (forming turtle groups). Thus, for marine turtles and other widely distributed marine species, integration of genetic and oceanographic data may enhance understanding of population connectivity and management requirements.

Ecology of Hawksbill Turtles, Eretmochelys imbricata, on a Western Caribbean Foraging Ground

Abstract We present results of an inwater research program focusing on basic ecology of juvenile hawksbill turtles (Eretmochelys imbricata) in the Cayman Islands. We made 206 captures of 135 hawksbills in Little Cayman and 103 captures of 97 hawksbills in Grand Cayman. The Cayman Islands aggregation demonstrated a broad size distribution (20.5–62.6 cm straight carapace length), slow growth rate (3.0 ± 0.9 cm/y), and multiple recaptures, suggesting long-term residence in some individuals. Demonstrated home range was small (mean distance from capture to recapture 545 ± 514 m, range 2–2080 m); although, an international tag return suggested a long-range developmental migration. Vertical features provided important habitat in Little Cayman, and larger turtles were generally captured in deeper waters. Behavior at sighting varied by habitat: resting, swimming, and feeding were observed in coral reef, reef wall, and hardbottom colonized by sponges and gorgonians, and resting was frequently observed in uncolonized hardbottom. Images obtained from underwater photographers show that hawksbills forage on sponges and occasionally on jellyfish. We observed an apparent commensal feeding relationship between hawksbills and 3 species of angelfish as well as aggressive interactions between hawksbills. We also documented causes of injury and mortality in the study area—including legal, illegal and incidental take, vessel collisions, hurricanes, and natural predation.

Harnessing recreational divers for the collection of sea turtle data around the Cayman Islands.

Here we present data from a 26-month program “Caribbean Turtle Watch,” initiated as part of the “Turtles in the Caribbean Overseas Territories” (TCOT) program and designed to harness recreational divers to assess in-water populations of marine turtles in the Cayman Islands. We recorded 521 dives in Grand Cayman and Little Cayman between September 1, 2002 and November 29, 2003. Data, presented as the mean number of turtles sighted per dive, provide insight into spatiotemporal patterns of sightings as a proxy of abundance. Widespread sightings were recorded of two marine turtle species, green turtles Chelonia mydas and hawksbill turtles Eretmochelys imbricata, around both islands. There was no obvious relationship between the existence of Marine Protected Areas (MPAs) and the abundance of turtle sightings. Diving is allowed in Marine Park Zones and dive pressure may impact overall habitat quality in these areas. The vast majority of sightings of both species (94% in each case) were considered to be juvenile or subadults. While turtle sighting potential was not a major influence on dive site choice, actual turtle sighting greatly enhanced dive enjoyment. Spatiotemporal and morphological analyses of data collected by volunteers compared favorably with those based on data collected by scientists. This technique is transferable to other countries and may hold particular value in areas where resources assigned to marine turtle research are low.

Investigating Potential for Depensation in Marine Turtles: How Low Can You Go?

Where mechanisms inherent within the biology of a species affect individual fitness at low density, demographic-scale depensation may occur, hastening further decline and leading ultimately to population extirpation and species extinction. Reduction in fertility at low population densities has been identified in marine and terrestrial species. Using data on hatch success and hatchling-emergence success as proxies for fertilization success, we conducted a global meta-analysis of data from breeding aggregations of green turtles (Chelonia mydas) and loggerhead turtles (Caretta caretta). We found that there has been no reduction in fertility in small nesting aggregations in either of these species worldwide. We considered mechanisms within the mating strategies and reproductive biology of marine turtles that may allow for novel genetic input and facilitate enhanced gene flow among rookeries. Behavioral reproductive mechanisms, such as natal philopatry and polyandry, may mitigate potential impacts of depensation and contribute to the resilience of these species.

Understanding implications of consumer behavior for wildlife farming and sustainable wildlife trade

Unsustainable wildlife trade affects biodiversity and the livelihoods of communities dependent upon those resources. Wildlife farming has been proposed to promote sustainable trade, but characterizing markets and understanding consumer behavior remain neglected but essential steps in the design and evaluation of such operations. We used sea turtle trade in the Cayman Islands, where turtles have been farm raised for human consumption for almost 50 years, as a case study to explore consumer preferences toward wild-sourced (illegal) and farmed (legal) products and potential conservation implications. Combining methods innovatively (including indirect questioning and choice experiments), we conducted a nationwide trade assessment through in-person interviews from September to December 2014. Households were randomly selected using disproportionate stratified sampling, and responses were weighted based on district population size. We approached 597 individuals, of which 37 (6.2%) refused to participate. Although 30% of households had consumed turtle in the previous 12 months, the purchase and consumption of wild products was rare (e.g., 64-742 resident households consumed wild turtle meat [i.e., 0.3-3.5% of households] but represented a large threat to wild turtles in the area due to their reduced populations). Differences among groups of consumers were marked, as identified through choice experiments, and price and source of product played important roles in their decisions. Despite the long-term practice of farming turtles, 13.5% of consumers showed a strong preference for wild products, which demonstrates the limitations of wildlife farming as a single tool for sustainable wildlife trade. By using a combination of indirect questioning, choice experiments, and sales data to investigate demand for wildlife products, we obtained insights about consumer behavior that can be used to develop conservation-demand-focused initiatives. Lack of data from long-term social-ecological assessments hinders the evaluation of and learning from wildlife farming. This information is key to understanding under which conditions different interventions (e.g., bans, wildlife farming, social marketing) are likely to succeed.

Biology and Ecology of the Coral Reefs of the Cayman Islands

The Cayman islands are three small low-lying subtropical islands in the NW Caribbean. The islands are tips of an underwater mountain chain and have a very narrow coastal shelf, usually of less than 1 km wide, which support considerable reef development. The major sublittoral habitats are coral reefs, lagoons, seagrass beds and mangroves, and fringing reefs shelter large areas of seagrasses and mangroves, the latter being important nursery areas also. There is a high diversity of marine invertebrates, with several molluscs and crustaceans providing commercially significant species. However, substantial recent developments have increased pressures on the marine systems, added to which more recently are stressors resulting from climate change. The islands are hit by hurricanes about once every 10 years, and suffer near-misses four times more often, which greatly affects these habitats. There are a number of different categories of Marine Protected Areas but even so, due to a number of direct anthropogenic stressors as well, coral cover has declined from 25 % to about 11 % over the past 15 years. Physical destruction from shipping and recreational boating has contributed significantly to this, as have various forms of pollution, dredging and shoreline construction, and poaching. The Marine Protected Area system is being reviewed, with specific measures to manage Grouper spawning aggregation sites, and a culling programme is underway in an attempt to control the invasive lionfish which pose the most recent threat to the coral reef fish communities.