The coastal waters of Baja California Sur, Mexico, include some of the most important foraging grounds of the East Pacific green turtle Chelonia mydas. However, they are also important fishing grounds for artisanal fleets, leading potentially to high levels of bycatch mortality. We studied the impact of a small-scale gill-net fishery at San Ignacio lagoon, north-west Mexico, an important green turtle feeding ground. We conducted mortality censuses and interviewed local fishers to estimate total bycatch mortality at the lagoon. We also used marked drifters and carcasses to estimate stranding probabilities of turtles taken as bycatch. During 2006–2009 we found 262 dead turtles; 96% of the mortality occurred in May–August corresponding to the fishing season for halibut Paralichthys californicus and guitar-fish (Rhinobatus sp.). Stranding probability estimated from drifters was 0.062 (95% confidence interval, CI, 0.035–0.094), yielding a minimum mortality of 3,516 turtles during 2006–2008 (95% CI 2,364–6,057) or 1,172 animals per year. This is probably an underestimate of real mortality as the drifters have higher stranding probabilities than carcasses and most of the nets were set in the lower lagoon where carcasses rarely strand. Interviews with local fishers yielded a similar estimate of 1,087 (95% CI 901–1,286) dead turtles per year. This study is emblematic of the impact of artisanal fleets on marine turtles caused by overlap of fishing and turtle feeding areas. In 2009 strandings declined by > 97%, resulting from a change in fishing practices because of increased vigilance by enforcement authorities, underscoring the importance of law enforcement to protect threatened species.

Monitoring of nesting beaches is often the only feasible and low-cost approach for assessing sea turtle populations. We investigated spatio-temporal patterns of sea turtle nesting activity monitored over 17 successive years in the Lamu archipelago, Kenya. Community-based patrols were conducted on 26 stretches of beach clustered in five major locations. A total of 2,021 nests were recorded: 1,971 (97.5%) green turtle Chelonia mydas nests, 31 (1.5%) hawksbill Eretmochelys imbricata nests, 8 (0.4%) olive ridley Lepidochelys olivacea nests and 11 (0.5%) unidentified nests. Nesting occurred year-round, increasing during March–July, when 74% of nests were recorded. A stable trend in mean annual nesting densities was observed in all locations. Mean clutch sizes were 117.7 ± SE 1 eggs (range 20–189) for green turtles, 103 ± SE 6 eggs (range 37–150) for hawksbill turtles, and 103 ± SE 6 eggs (range 80–133) for olive ridley turtles. Curved carapace length for green turtles was 65–125 cm, and mean annual incubation duration was 55.5 ± SE 0.05 days. The mean incubation duration for green turtle nests differed significantly between months and seasons but not locations. The hatching success (pooled data) was 81.3% (n = 1,841) and was higher for in situ nests (81.0 ± SE 1.5%) compared to relocated nests (77.8 ± SE 1.4%). The results highlight the important contribution of community-based monitoring in Kenya to sustaining the sea turtle populations of the Western Indian Ocean region.

Ostional in Costa Rica is the second largest nesting site of the olive ridley sea turtle Lepidochelys olivacea, which is categorized as Vulnerable on the IUCN Red List. In Ostional the local community helps maintain the nesting site and collects olive ridley eggs for consumption and trade within Costa Rica. Since its inception in 1987 the egg harvesting project has integrated sea turtle conservation with community development. We assessed the current status of this project in terms of community awareness, dependency, involvement and perceptions, using a household survey and semi-structured interviews with key informants. We also compared some of our findings with those of previous studies at the site, finding that the project has fewer dependents, primary livelihood activities have shifted towards tourism and hospitality, and respondents are more aware about environmental conservation and stewardship. We map outcomes of the project with the Sustainable Livelihoods Framework, and suggest that further capacity building for research and tourism could contribute towards sustaining the turtle population, local livelihoods, and the community-based conservation institution.

The Guadeloupe archipelago hosts nesting of the threatened hawksbill Eretmochelys imbricata, green Chelonia mydas and leatherback Dermochelys coriacea marine turtles. There is a need to monitor the nesting of these species but, with > 150 beaches in the archipelago, exhaustive monitoring is infeasible. Using a new monitoring design and a new statistical tool we have been able to monitor one-third of the beaches. Seasonality and level of nesting were described for the three species for 2 years on > 50 beaches. For each species beaches were categorized as A- or B-beaches, with high and low nest density, respectively. A-beaches were monitored on 6–7 days per month before and after the peak nesting period and on 7–15 days during the peak, and the B-beaches on 14–22 days during the peak. The monitoring design and statistical tool are described in detail as they could be applied to any migratory species. Hawksbill turtles at Trois Ilets beach have been monitored for 9 years and a positive trend in nesting has been detected.

Turtle trade in the fish markets of Alexandria was reported up to the late 1990s, motivating conservation initiatives and enforcement of legal protection. To assess the current trade and bycatch levels in Alexandria and other ports we carried out an interview survey of 445 people in 2007, mostly fishermen and fishmongers, in 15 coastal cities and fishing ports along the Mediterranean coast of Egypt. The declared catch rates and official fishing fleet statistics suggest that captures of loggerhead Caretta caretta and green turtles Chelonia mydas are in the order of several thousands per year, possibly > 7,000 per year, mainly from trawling, longlining and set nets. Probably several hundred turtles die each year as a consequence of the high mortality rates typical of these fishing gears. In addition, most fishermen from Alexandria and some fishermen from other regions declared that they kill turtles for meat. Regulations and enforcement appear to be ineffective, as turtles are usually killed and consumed on board or only their meat is landed. Some turtles are still traded on the black market in some Alexandria fish markets. The overall mortality probably represents an unsustainable toll on the Mediterranean loggerhead and green turtle populations, and the perception of fishermen is that turtle numbers are declining. Mitigating the identified threats is thus urgent. In particular, intentional killing should be tackled through its cultural drivers, and measures to reduce bycatch mortality need to be tested and implemented.

Recovery plans for the Endangered loggerhead marine turtle Caretta caretta cite mammalian predation as a major threat, and recommend nest protection efforts, already present at many rookery beaches, to protect eggs and hatchlings. Nest protection techniques vary but wire box cages and plastic mesh screens are two common tools used to deter predation by a host of beach-foraging, opportunistic mammalian predators. We empirically tested the efficacy of wire cages and plastic mesh screens in preventing red fox Vulpes vulpes predation on artificial nests. Both techniques averted fox predation (0%), whereas unprotected control nests suffered 33% predation under conditions of normal predator motivation, or a level of motivation stimulated by loggerhead turtle egg scent. However, in side-by-side comparisons under conditions of presumed high predator motivation, 25% of mesh screens were breached whereas no cage-protected nests were successfully predated. In addition to effectiveness at preventing predation, factors such as cost, ease of use, deployment time, and magnetic disturbance were evaluated. Our study suggests that the efficacy of plastic screens and the potential disadvantages associated with galvanized wire should influence selection of mechanical barriers on beaches where fox predation threatens loggerhead nests.

Reunion Island in the south-west Indian Ocean once had significant nesting populations of marine turtles but they declined rapidly after human colonization. In 1996, after regular sightings of turtles offshore, an aerial survey programme was initiated to monitor the occurrence of marine turtles and their distribution along the west coast of the island. Between 1998 and 2008, along a 30-km coastline transect between Saint Leu and Saint Paul, a total of 1,845 marine turtle sightings were recorded during 146 flights with an ultralight aircraft. The mean number of turtle sightings per survey increased significantly between 1998 and 2008, and a variety of sizes were recorded throughout the year. Marine turtles were found over coral reef zones and on the outer reef slopes. Spatial distribution may be linked to the topography and substrate of the bottom, which determine the availability of food and shelter. The marine protected area located off Saint Paul seems to have benefited marine turtles as they frequent this area more than other regions on the west coast. These results are encouraging for local organizations working for the conservation of marine turtles on Reunion Island.

The estimated number of olive ridley marine turtles Lepidochelys olivacea nesting annually in 2002–2007 in French Guiana was 1,716–3,257, the highest ever recorded in the country and similar to nesting numbers recorded in neighbouring Suriname c. 40 years ago, where the species has now severely declined. A shift of nesting females from Suriname to French Guiana beaches and improvement of nationwide marine turtle monitoring appear to be the most plausible explanations for the current high level of nesting recorded in French Guiana. The species' nesting status in French Guiana therefore appears less critical than previously documented but ongoing threats suggest the need to reinforce regional conservation efforts in the West Atlantic.

The leatherback turtle Dermochelys coriacea, the only extant species in its family, is categorized as Vulnerable on the IUCN Red List. The protection of nesting beaches and the associated conservation efforts along the Western Atlantic coast of Central America have improved the population trends of some of the most important rookeries. Here we report the life history, ecology and population trends of leatherback turtles over 18 years (1994–2012, excluding 1998) of effective protection in the Pacuare Nature Reserve, on the Caribbean coast of Costa Rica. A mean density of 142 nests per km, probably the highest in Central America, indicates the importance of this rookery within the Caribbean region. Long-term conservation efforts at the Reserve have significantly reduced poaching and contributed to maintaining a high level of hatchling production. Long-term monitoring has also facilitated estimation of relevant demographic parameters of the population, such as nesting success (mean 69.8 ± SD 7.3%), clutch size (which is positively correlated with female size), hatching success (mean 55.2 ± SD 6.0%), remigration interval (2.5 years), and growth rate of remigrant females (mean 0.3 ± SD 1.0 cm per year), which is slightly faster than growth rates reported for Pacific leatherback turtles. Overall, efforts at Pacuare have been successful in protecting leatherback turtles and understanding their life history, highlighting the importance of long-term conservation projects for maintaining threatened leatherback populations.

We used satellite telemetry to identify in-water habitat used by individuals in the smallest North-west Atlantic subpopulation of adult nesting loggerhead turtles Caretta caretta during the breeding season. During 2010, 2011 and 2012 breeding periods, a total of 20 adult females used habitats proximal to nesting beaches with various levels of protection within Dry Tortugas National Park. We then used a rapid, high-resolution, digital imaging system to map habitat adjacent to nesting beaches, revealing the diversity and distribution of available benthic cover. Turtle behaviour showing measurable site-fidelity to these diverse habitats has implications for managing protected areas and human activities within them. Protecting diverse benthic areas adjacent to loggerhead turtle nesting beaches here and elsewhere could provide benefits for overall biodiversity conservation.

Nest predation can threaten marine turtle nesting success, and having to address dissimilar predator species complicates nest protection efforts. On Florida's Keewaydin Island predation by raccoons Procyon lotor and invasive feral swine Sus scrofa are disparate, significant threats to marine turtle nests. Using 6 years of nesting data (mostly for loggerhead marine turtles Caretta caretta) we examined the impacts of swine predation on nests and the benefits of swine eradication, caging nests to protect them from raccoon predation, and the effects of nest caging on swine predation. Nest predation by swine began in mid nesting season 2007, after which swine quickly annihilated all remaining marine turtle nests. During 2005–2010 raccoon predation rates for caged nests (0.7–20.4%) were significantly lower than for uncaged nests (5.6–68.8%) in every year except 2009, when little raccoon predation occurred. The proportions of eggs lost from raccoon-predated nests did not differ between caged and uncaged nests. Caging did not prevent destruction by swine but median survival time for caged nests was 11.5 days longer than for uncaged nests, indicating that caged eggs in nests have a greater chance of hatching before being predated by swine. The financial cost of the eradication of swine greatly outweighed the value of hatchlings lost to swine predation in 2007.

Globally, marine turtles are considered threatened throughout their range, and therefore conservation practitioners are increasingly investing resources in marine protected areas to protect key life history stages and critical habitats, including foraging grounds, nesting beaches and inter-nesting areas. Empirical data on the distribution of these habitats and/or the spatial ecology and behaviour of individuals of many marine turtle populations are often lacking, undermining conservation efforts, particularly along the Atlantic coast of Africa. Here we contribute to the knowledge base in this region by describing patterns of habitat use for nine green turtles Chelonia mydas tagged with satellite platform transmitter terminals at a foraging ground in Loango Bay, Republic of the Congo, one of only a few documented mainland foraging grounds for marine turtles in Central Africa. Analyses of these data revealed that core areas of habitat use and occupancy for a wide range of size/age classes were restricted to shallow waters adjacent to Pointe Indienne in Loango Bay, with most individuals showing periods of high fidelity to this area. These data are timely given the Congolese government recently announced its intention to create a marine conservation zone to protect marine turtles in Loango Bay. Despite the small sample size of this study, these data exemplify the need for comprehensive strategies that span national jurisdictions, as we provide the first documented evidence of linkages between green turtle foraging sites in Central Africa (Loango Bay, Republic of the Congo) and Southern Africa (Mussulo Bay, Angola).

The impact of fisheries on marine megafauna is widely known but most studies have focused on commercial fisheries, overlooking the effect of local recreational fisheries. This is particularly important for marine turtles in near-shore habitats that overlap with recreational fisheries. We assessed the effect of recreational scallop fisheries on the distribution and behaviour of foraging marine turtles in the coastal waters of the upper Eastern Gulf of Mexico. Before and during the scallop season we quantified the density and overlap of marine turtles and vessels sighted, and satellite tracked four turtles to assess their distribution and behaviour. The relative distribution of marine turtles sighted during the scallop season overlapped with 48% of the area most frequently used by harvesters, and marine turtle activity hotspots shifted between seasons. In addition, during the scallop season the home range size of individual turtles appeared to decrease, and turtles displayed frequent changes in travel speed and directionality. We hypothesize that such changes are probably related to the distribution and movement of vessels and the abundant presence of people in the water. Our study highlights the importance of considering recreational fisheries and their local effect on marine megafauna for informing future adaptive management practices. However, further studies are needed to quantify the direct and indirect impacts of recreational fisheries and to assess the degree of risk of associated activities to marine turtle populations.

For many species abundance data from across their entire range are incomplete, and therefore it is difficult to accurately assess their conservation status. Even for species that are large, charismatic and relatively easy to study, conservation assessments are often hampered by lack of data. Here we report a marked, previously undescribed, increase in numbers at a breeding colony of the loggerhead turtle Caretta caretta, a species that is Critically Endangered in several parts of its range, and place this report in the global context for this species. We present a 10-year (2008–2017) dataset of nesting activities for this species on the island of Sal, one of the Cape Verde islands in the Atlantic Ocean. Foot patrols recorded 21,938 nests during the study period. We estimate that the annual number of nests on Sal increased from 506 in 2008 to 7,771 in 2017. Taking into account that there are only two known loggerhead turtle rookeries (on Masirah Island, Oman, and in Florida, USA) with > 50,000 nests reported annually, and few with > 1,000 nests per year, our results suggest that Sal is one of the 10 largest loggerhead turtle rookeries globally. Our work highlights the conservation significance of reporting trends in abundance at breeding sites for marine turtles and other taxa.

The South Pacific subpopulation of the loggerhead turtle Caretta caretta is categorized as Critically Endangered on the IUCN Red List because of significant population declines. Five Queensland beaches support high-density nesting of this subpopulation, but egg and hatchling survival are low at some beaches because of feral and native terrestrial predators. We quantified predation of loggerhead turtle eggs by two species of goanna, Varanus panoptes and Varanus varius, at Wreck Rock beach, one of the turtle's major nesting beaches. In addition, we conducted an experiment to determine the efficacy of a nest protection device. Predation rates at Wreck Rock beach were 15.2% for treatment and 45.8% for non-treatment clutches during the 2013–2014 nesting season. A higher probability of predation (64%) was predicted for the northern beach. Although nests were only partially predated (16.4% of the total number of eggs), nest loss to predators and beach erosion (caused by a cyclone) was 91.7%. If left unmanaged, the cumulative impact of predation and other threats, including those exacerbated by climate change, can cause unsustainable loss of loggerhead turtle nests. This study provides one of the first quantitative data sets on rates of loggerhead turtle clutch predation in the South Pacific. It enhances our understanding of goanna predation impacts and identifies an efficient predator exclusion device for mitigating the effects of terrestrial predators at Wreck Rock beach, and for protecting marine turtle nests across northern Australia and globally.

Bycatch of non-target animals in small-scale fisheries poses a major threat to seabirds and marine mammals and turtles. This is also a problem for small-scale fisheries in Peru because of the magnitude of these fisheries and the important marine biodiversity in Peruvian waters. Here we describe how we implemented a novel approach to mitigate bycatch impacts on marine turtles in Peru. We used high-frequency (HF) two-way radio communication to exchange information with fishers. We sought data that would afford insights into fishing patterns and levels of turtle bycatch so that we could identify areas of high-density bycatch in real time and warn other fishers. In return we provided oceanographic and atmospheric information useful for the fishers. Radio communication also served as a platform to promote the use of safe handling and release techniques for incidentally caught animals. During the 24 months of the programme we communicated with over 200 vessels and with 200–1,400 fishers, who used primarily longlines, gillnets, jiggers, purse seiners and trawlers. Our findings suggest that HF radio communication is a useful tool (low cost and widely used by fishers, with extensive spatial coverage), helps build links with fishers that potentially reduces fishery impacts on marine turtles, and can also provide information on poorly documented fisheries and the relevant bycatch data associated with small-scale fishing practices.

Global marine turtle population assessments highlight the importance of the south-west Indian Ocean region, despite data gaps for the Chagos Archipelago. The archipelago hosts nesting hawksbill Eretmochelys imbricata and green turtles Chelonia mydas, both heavily exploited for 2 centuries until protection in 1968–1970. We assessed available nesting habitat and spatial distribution of nesting activity during rapid surveys of 90% of the archipelago's coastline in 1996, 1999, 2006 and 2016. We quantified seasonality and mean annual egg clutch production from monthly track counts during 2006–2018 along a 2.8 km index beach on Diego Garcia island. An estimated 56% (132 km) of coastline provided suitable nesting habitat. Diego Garcia and Peros Banhos atolls accounted for 90.4% of hawksbill and 70.4% of green turtle nesting. Hawksbill turtles showed distinct nesting peaks during October–February, and green turtles nested year-round with elevated activity during June–October. Estimates of 6,300 hawksbill and 20,500 green turtle clutches laid annually during 2011–2018 indicate that nesting on the Chagos Archipelago has increased 2–5 times for hawksbill turtles and 4–9 times for green turtles since 1996. Regional estimates indicate green turtles produce 10 times more egg clutches than hawksbill turtles, and the Chagos Archipelago accounts for 39–51% of an estimated 12,500–16,000 hawksbill and 14–20% of an estimated 104,000–143,500 green turtle clutches laid in the south-west Indian Ocean. The improved status may reflect > 40 years without significant exploitation. Long-term monitoring is needed to captureinterannual variation in nesting numbers and minimize uncertainty in population estimates.

Predation can be an important driver of population dynamics but can also pose a dilemma to conservation managers if the species interacting are of conservation concern or have a high public profile. For 5 years we conducted regular transect surveys to monitor the spatial and temporal patterns of predation of adult marine turtles by jaguars Panthera onca in Tortuguero National Park, Costa Rica. Predation occurs throughout the study site on Tortuguero Beach although at lower rates at the northern and southern ends, probably because of increased human presence in these areas. There was a marked increase in predation, from an average of < 2 turtles predated per survey in the first season to > 5 predated per survey in the last, with 676 jaguar-predated marine turtles recorded during the study period. With a minimum of 189 individuals predated in the last season, predation of adult turtles has now reached a magnitude never before recorded in a marine turtle rookery. Although the nesting population of marine turtles in Tortuguero is one of the largest in the world and suffers from both direct and indirect anthropogenic pressures, the increase in predation by jaguars makes this ecological interaction relevant to the management of both the jaguar and marine turtle populations. The situation could lead to a potential conflict in conservation strategies that, given the flagship role of the species involved, will need to be addressed both in the context of species management and conservation marketing.

Ecotourism is often suggested as a tool for promoting conservation but evidence for its usefulness is mixed. The success of conservation projects is widely recognized to depend upon the positive attitudes of local communities and thus it is important to know if ecotourism affects local perceptions of natural resources and conservation, as these can be important determinants of conservation behaviour. Rapid Rural Appraisal and questionnaire-based interviews were used to investigate this issue in the village of Grande Riviere, Trinidad. This has a community-based ecotourism programme for leatherback turtles Dermochelys coriacea, and is also one of the few sites where the Critically Endangered endemic Trinidad piping-guan Pipile pipile may be sighted. Topics addressed were knowledge and awareness of local conservation issues, focusing on attitudes to the environment in general, turtles and the Trinidad piping-guan. Ecotourism significantly affected perceptions. Villagers showed more awareness and support for turtle conservation than for the piping-guan or any other wildlife. Moreover, those households directly benefiting from the ecotourism industry had better knowledge of local natural resources and greater general awareness of conservation issues (not limited to turtles). Other socio-economic factors such as education and income also affected attitudes and knowledge but the ecotourism effect was still present after accounting for these. Hunting was seen as the main threat to wildlife but was also a popular pastime, illustrating the potential for mismatch between attitudes and conservation behaviours.

Situated in the northernmost part of Mozambique, the northern Querimbas Islands support some of the most diverse and pristine coral reefs in the Western Indian Ocean. The community-based turtle conservation programme that we developed on Vamizi Island has facilitated the identification and protection of a key nesting site for the green marine turtle Chelonia mydas in Mozambique, with a mean of 122 nests per year. The area is also used by nesting female and immature hawksbill turtles Eretmochelys imbricata. Nesting activity of green turtles was observed all year round, with a peak in the summer (February–March). Incubation periods of this species showed seasonal fluctuations inversely correlated with air temperature. Hatching success was high (87%) when nests were not lost through tidal overwash and erosion, which affected nearly 40% of all nests in 2007. Using satellite tracking of four green turtles nesting on Vamizi we identified foraging grounds in marine protected areas in Kenya, Tanzania and north-west Madagascar. Migratory routes of two individuals along the East African coast were generally neritic and all passed through the waters of multiple nations and as many as six marine conservation areas, emphasizing the importance of regional cooperation. Awareness programmes were also conducted with resource users, and the development of a community-based management system triggered the creation of a marine sanctuary by the local community.