Olive Ridley Turtles Lepidochelys Olivacea Research Articles

Conservation of sea turtles on the beach areas from Sonadia Island to Saint Martin’s Island in the Bay of Bengal in Bangladesh

Five species of sea turtle are known to nest on the coastal beaches of Bangladesh: Loggerhead Sea Turtle Caretta caretta, Green Sea Turtle Chelonia mydas, Hawksbill Sea Turtle Eretmochelys imbricata, Olive Ridley Turtle Lepidochelys olivacea, and Leatherback Sea Turtle Dermochelys coriacea. Olive Ridleys are more common than Green Turtles, and the others are very rare. Sea turtle hatcheries were visited on the Bay of Bengal beaches running from Sonadia Island to the Saint Martin’s Island Beaches of Cox’s Bazar in Bangladesh, from January to March 2022. During this period 22 hatcheries were found operating in the field, of which 11 were maintained by Marine Life Alliance, eight by NACOM (Nature Conservation Management) and two by CODEC (Community Development Centre); one was anonymous. Only Olive Ridley Turtles nesting was recorded during 2021–22. CODEC recorded 26 nests and collected 2,943 eggs for hatcheries, which released 1,612 healthy hatchings into the Bay of Bengal. The clutch size was 21–165 (average 103, n = 26), and the incubation period was 45–75 days (average 53 days, n = 1,612). The higher air temperature from March to May hastened the hatching process. NGOs are working on conservation aspects of the sea turtles, mostly by collecting eggs and releasing hatchlings into the Bay of Bengal. They have also prepared booklets and posters, hoisted banners, published papers, and organised seminars, rallies and workshops for education and awareness of the local people. These initiatives are encouraging, but it may be better if the efforts of NGOs to support sea turtle conservation were more integrated.

First report of Rhytidodes gelatinosus (Rudolphi, 1819) Looss, 1901 (Digenea: Rhytidodidae) in an olive-ridley Turtle Lepidochelys olivacea (Eschscholtz, 1829) from Brazil.

This article reports the first occurrence of Rhytidodes gelatinosus (Rudolphi, 1819) Looss, 1901 (Digenea: Rhytidodidae) in the olive-ridley turtle Lepidochelys olivacea (Testudines: Chelonidae), in an individual found in the State of Sergipe, Brazil. Although R. gelatinosus has already been described in other species of sea turtles in the world, this is the first report of this parasite in L. olivacea. We also present a list of hosts and locations where this helminth has already been identified.

Marine pollution between gyres: plastic debris in marine turtles and dolphins in French Guiana, Equatorial Atlantic

Plastic pollution has not raised much attention until the 2000s, despite being manufactured for about a century. It is now considered one of the most substantial environmental issues. Here we investigate the presence of plastic contamination in 34 stranded animals on the coast of French Guiana, South America. Here we present information highlighting the magnitude of plastic contamination in marine coastal and pelagic tropical marine vertebrates on the Equatorial Atlantic coast of South America. All four species studied here are protected and emblematic vertebrates of the region, with a fragile conservation status, including the olive ridley turtle Lepidochelys olivacea, the green turtle Chelonia mydas and the leatherback turtle Dermochelys coriacea, and a small cetacean, the Guiana dolphin Sotalia guianensis. Macroplastics (polypropylene, polyethylene, terephthalate, and polystyrene) were detected in four juvenile green turtles. Microplastics (polypropylene, polyethylene, terephthalate, polystyrene, nylon, acrylates, polycarbonates) were found in 13 individuals (two dolphins, six olive ridleys, four green turtles, and the leatherback turtle). The sampled species have different diets, distribution patterns, and ages, suggesting widespread plastic pollution. The study area is located far from the oceanic gyres. However, they are influenced by the North Brazilian Current, the Amazon River, and other rivers of the Guianas.

Paresis as a limiting factor in the reproductive efficiency of a nesting colony of Lepidochelys olivacea (Eschscholtz, 1829) in La Escobilla beach, Oaxaca, Mexico

Rear flippers are crucial in the nesting process of Olive Ridley Turtles Lepidochelys olivacea, so any impact on them could constitute a limiting factor in reproductive efficiency. Muscle weakness of the rear legs has been observed in some nesting females on La Escobilla beach in Oaxaca state, Mexico; however, this disorder has not been sufficiently researched. The aim of this study was to identify and describe this problem in a nesting colony of L. olivacea in La Escobilla. We obtained the biochemical profiles of eight females with clinical signs of muscle weakness of the rear legs, that could not build the incubation chamber for their nest. In order to compare their blood characteristics, we selected eight seemingly healthy turtles that successfully built their nests, laid eggs through oviposition and covered the nest. We found no significant differences in most of the blood parameters, except for Creatinine-Kinase (CK). Female turtles with muscle weakness presented significantly higher concentrations of CK (t = 2.1448, d.f. = 2, P <0.0001) when compared to the healthy turtles. CK is an appropriate enzyme for identifying the integrity of the muscle cell and is a muscle damage indicator. Our hypothesis is that the paresis observed in the rear legs of the female turtles in La Escobilla could be a chronic debilitation caused by a gradual exposure to biotoxins such as saxitoxins.

Leucism: the prevalent congenital malformation in the olive ridley sea turtle of northwestern Mexico

Despite being the most abundant sea turtle in the world, the olive ridley turtle Lepidochelys olivacea is classified as Vulnerable by the IUCN. There is evidence of congenital malformations in hatchlings, and the associated causes are multifactorial, with both genetic and environmental sources. Santuario Playa Ceuta (SPC) is a sanctuary for the olive ridley, located at the northernmost region of its nesting range in the Mexican Pacific. The objective of this study was to identify and quantify the prevalence and severity of congenital malformations in olive ridley embryos/hatchlings in SPC during the 2017 nesting season. We collected 62907 eggs from 643 relocated nests that were moved to a hatchery, of which 4242 eggs with obvious development did not hatch and were analyzed for this study. Hatching success was 53.9%, with 22.5% of nests (n = 145) and 0.54% of eggs (n = 344) showing embryos or hatchlings with malformations. The nest severity index was 2.4 (range: 1-10) malformed embryos or hatchlings per nest, and the organism severity index was 1.4 (range: 1-7) malformations per malformed embryo or hatchling. Leucism was the most prevalent malformation (34.4%; 170/494 total observed), with the craniofacial region showing the greatest diversity of malformations (17/35 types). Given the geographical position of SPC, extreme environmental conditions (e.g. cold, heat, and dryness) could be one of the main causes of teratogenesis in this species. However, more studies are needed regarding the presence of contaminants, genetic factors, health assessments of nesting females, and malformation rates of nests that remain in situ versus those that are relocated.

A Mitigation Hierarchy Approach for Managing Sea Turtle Captures in Small-Scale Fisheries

The mitigation hierarchy has been proposed as an overarching framework for managing fisheries and reducing marine megafauna bycatch, but requires empirical application to show its practical utility. Focusing on a small-scale fishing community in Peru as a case study system, we test how the mitigation hierarchy can support efforts to reduce captures of sea turtles in gillnets and link these actions to broader goals for biodiversity. We evaluate three management scenarios by drawing on ecological risk assessment (ERA) and qualitative management strategy evaluation to assess trade-offs between biological, economic, and social considerations. The turtle species of management focus include leatherback turtle Dermochelys coriacea, green turtle Chelonia mydas, and olive ridley turtle Lepidochelys olivacea. Adopting a mixed-methods iterative approach to data collection, we undertook a literature review to collate secondary data on the fishery and the species of turtles captured. We then collected primary data to fill the knowledge gaps identified, including establishing the spatial extent of the fishery and calculating turtle capture rates for the fishery. We identified and evaluated the potential risk that the fishery poses to each turtle species within Pacific East regional management units using a qualitative ERA. Finally, we evaluated potential management strategies to reduce turtle captures, incorporating stakeholder preference from questionnaire-based surveys and considering preliminary estimates of trends across a range of performance indicators. We illustrate how the proposed framework can integrate existing knowledge on an issue of marine megafauna captures, and incorporate established decision-making processes to help identify data gaps. This supports a holistic assessment of management strategies towards biodiversity goals standardized across fisheries and scales.

Spatial distribution of epibionts on olive ridley sea turtles at Playa Ostional, Costa Rica.

There is a wealth of published information on the epibiont communities of sea turtles, yet many of these studies have exclusively sampled epibionts found only on the carapace. Considering that epibionts may be found on almost all body-surfaces and that it is highly plausible to expect different regions of the body to host distinct epibiont taxa, there is a need for quantitative information on the spatial variation of epibiont communities on turtles. To achieve this, we measured how total epibiont abundance and biomass on olive ridley turtles Lepidochelys olivacea varies among four body-areas of the hosts (n = 30). We showed that epibiont loads on olive ridleys are higher, both in terms of number and biomass, on the skin than they are on the carapace or plastron. This contrasts with previous findings for other hard-shelled sea turtles, where epibionts are usually more abundant on the carapace or plastron. Moreover, the arguably most ubiquitous epibiont taxon for other hard-shelled sea turtles, the barnacle Chelonibia spp., only occurred in relatively low numbers on olive ridleys and the barnacles Stomatolepas elegans and Platylepas hexastylos are far more abundant. We postulate that these differences between the epibiont communities of different sea turtle taxa could indicate that the carapaces of olive ridley turtles provide a more challenging substratum for epibionts than do the hard shells of other sea turtles. In addition, we conclude that it is important to conduct full body surveys when attempting to produce a holistic qualitative or quantitative characterization of the epibiont communities of sea turtles.

First report of fibropapillomatosis in an olive ridley turtle Lepidochelys olivacea from the southeastern Pacific.

An adult olive ridley turtle Lepidochelys olivacea with lesions suggestive of fibropapillomatosis was rescued on the coast of San Antonio, central Chile. Histopathologic analysis showed an exophytic and pedunculated mass formed by epidermal papillary projections supported by fibrovascular cores, epidermal hyperplasia and marked orthokeratotic hyperkeratosis. ChHV5 unique long genes UL27, UL28 and UL30 were amplified from tumor lesions and sequenced for phylogeny. Phylogenetic reconstruction showed the Chilean sequences clustering with the Eastern Pacific group. This is the first case of fibropapillomatosis in an olive ridley turtle diagnosed in Chile and in the southeastern Pacific region. Our results suggest a regional grouping of ChHV5 variants independent of the marine turtle's species.

A convolutional neural network for detecting sea turtles in drone imagery

Abstract Marine megafauna are difficult to observe and count because many species travel widely and spend large amounts of time submerged. As such, management programmes seeking to conserve these species are often hampered by limited information about population levels. Unoccupied aircraft systems (UAS, aka drones) provide a potentially useful technique for assessing marine animal populations, but a central challenge lies in analysing the vast amounts of data generated in the images or video acquired during each flight. Neural networks are emerging as a powerful tool for automating object detection across data domains and can be applied to UAS imagery to generate new population‐level insights. To explore the utility of these emerging technologies in a challenging field setting, we used neural networks to enumerate olive ridley turtles Lepidochelys olivacea in drone images acquired during a mass‐nesting event on the coast of Ostional, Costa Rica. Results revealed substantial promise for this approach; specifically, our model detected 8% more turtles than manual counts while effectively reducing the manual validation burden from 2,971,554 to 44,822 image windows. Our detection pipeline was trained on a relatively small set of turtle examples (N = 944), implying that this method can be easily bootstrapped for other applications, and is practical with real‐world UAS datasets. Our findings highlight the feasibility of combining UAS and neural networks to estimate population levels of diverse marine animals and suggest that the automation inherent in these techniques will soon permit monitoring over spatial and temporal scales that would previously have been impractical.

Identification and evaluation of semiochemicals for the biological control of the beetle Omorgus suberosus (F.) (Coleoptera: Trogidae), a facultative predator of eggs of the sea turtle Lepidochelys olivacea (Eschscholtz).

The beetle Omorgus suberosus (F.) is a facultative predator of eggs of the olive ridley turtle Lepidochelys olivacea (Eschscholtz). Laboratory and field investigations were conducted in order to characterize volatile attractants of O. suberosus and to explore the potential for application of these volatiles in a selective mass trapping method. Headspace sorptive extraction (HSSE) coupled to thermo-desorption gas chromatography–mass spectrometry (TD-GC-MS) analysis of the volatile constituents from beetles or turtle nests revealed 24 potential compounds. However, electroantennographic (EAG) measurements revealed antennal sensitivity only to indole, linoleic acid, trimethylamine, dimethyl sulphide, dimethyl disulphide and ammonia. Behavioural tests showed that these compounds are highly attractive to O. suberosus. Field trapping experiments revealed that indole and ammonia were more attractive than the other volatile compounds and showed similar attractiveness to that produced by conventional baits (chicken feathers). The use of a combined bait of indole and NH3 would therefore be the most effective trap design. The data presented are the first to demonstrate effective massive capture of O. suberosus using an attractant-based trapping method. These findings have potential for the development of an efficient mass trapping method for control of this beetle as part of efforts towards conservation of L. olivacea at La Escobilla in Oaxaca, Mexico.

Going the extra mile: Ground-based monitoring of olive ridley turtles reveals Gabon hosts the largest rookery in the Atlantic

The management of widely dispersed marine vertebrates can be facilitated by better understanding their distribution, density, population trends and threats. Unfortunately, for some populations of sea turtle spatial and temporal data are often lacking, particularly along the Atlantic coast of Africa, a region which is considered globally important. Here we combined spatially limited monitoring data from four nesting beaches over seven seasons with an extensive ground-based coastal survey that covered 585km of Gabon’s Atlantic coast, to provide the first population assessment for the olive ridley turtle Lepidochelys olivacea. This species is currently classified as data deficient by the IUCN in the eastern Atlantic and so is considered a regional conservation priority. Whilst the logistics required to undertake such a comprehensive ground-based census were complicated, the method proved extremely effective in providing population estimates for a widely dispersed marine vertebrate and demonstrates the importance of focusing beyond intensively monitored beaches. In particular, our findings reveal that the presence of nesting activity spans almost the entirety of Gabon’s coast, the density of which subsequently reveals that Gabon hosts one of the most important olive ridley rookeries in the Atlantic (2370–9814 clutches, approximating to 948–5452 breeding females per annum and a total estimate of 1422–8178 breeding females), with a significant proportion, 81±3.5% (mean±1 S.D.) of total nesting effort occurring within protected areas. These findings thus complement our existing knowledge base and further emphasise the regional and global importance of Gabon’s nesting sea turtle populations.

Dispersal and dive patterns during the post-nesting migration of olive ridley turtles from French Guiana

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 26:221-234 (2015) - DOI: https://doi.org/10.3354/esr00625 Dispersal and dive patterns during the post-nesting migration of olive ridley turtles from French Guiana Virginie Plot1,2,4,*, Benoit de Thoisy3, Jean-Yves Georges1,2 1Institut Pluridisciplinaire Hubert Curien (IPHC), Université de Strasbourg, Strasbourg 67087, France 2CNRS, UMR 7178, Strasbourg 67087, France 3Kwata Association, 16 avenue Louis Pasteur, 97335 Cayenne, French Guiana 4Present address: Université de la Réunion, Laboratoire ECOMAR, 97715 Saint Denis, Ile de la Réunion, France *Corresponding author: v.plot@hotmail.fr ABSTRACT: Behavioral plasticity allows migrating animals to adjust their migration patterns in relation to the environmental conditions they encounter during their movements. Sea turtles display long post-nesting migrations which vary considerably between species and populations. To date, there has been no description of migratory patterns of the large population of olive ridley turtles Lepidochelys olivacea in the west Atlantic. Here, we investigated dispersal and dive patterns in relation to environmental conditions of 7 satellite-tracked olive ridley females from French Guiana during their post-nesting migration. After they left the nesting beach, turtles followed a consistent northwestward direction and then remained in the restricted yet productive neritic domain of the continental shelf of French Guiana and Suriname. Despite this restricted dispersal range, turtles demonstrated variability in the habitats they exploited, i.e. the coastline, the continental shelf, and the continental slope, illustrating some plasticity. Moreover, turtles showed 2 different foraging strategies, either directly reaching a specific foraging area off river mouths, or meandering over the neritic area exploiting several foraging areas. In addition, turtles showed different dive patterns related to their habitat, although mostly exploiting the seabed by routinely performing U-shaped benthic dives. Overall, turtles vertically exploited non-stratified water masses characterized by warm surface temperatures consistent with their preferential thermal habitat. The migration strategy used by olive ridleys from French Guiana raises conservation concerns, since turtles may be exposed to coastal human-induced activities that must be considered in the implementation of accurate management measures for this still poorly studied population. KEY WORDS: Migration strategy · Diving behavior · Satellite tracking · Atlantic Ocean · Olive ridley turtle Full text in pdf format Supplementary material PreviousNextCite this article as: Plot V, de Thoisy B, Georges JY (2015) Dispersal and dive patterns during the post-nesting migration of olive ridley turtles from French Guiana. Endang Species Res 26:221-234. https://doi.org/10.3354/esr00625 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 26, No. 3. Online publication date: January 22, 2015 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2015 Inter-Research.

Marine turtle mortalities along the Tamil Nadu coast of India and the need for turtle-friendly fisheries

In the past two decades, sea turtle mortality has increased due to a variety of anthropogenic activities along the Nagapattinam and Chennai coast region in Tamil Nadu, South India. Weekly field surveys were conducted over an eight-month period from December 2013 to July 2014 to monitor the mortality of turtles in these coastal areas, revealing a notable disruption in the nesting activity of the turtles during January–March; the worst affected were mature individuals. Anthropogenic activities like boat strikes and fishing activity were recorded as the major causes of turtle death within this region. This paper highlights the need for better turtle monitoring systems within this part of South India, particularly for endangered species like the olive ridley turtle (Lepidochelys olivacea), whilst also suggesting suitable conservation measures to protect them.

Defining olive ridley turtle Lepidochelys olivacea management units in Australia and assessing the potential impact of mortality in ghost nets

In Australia, the olive ridley sea turtle Lepidochelys olivacea has received little re - search attention and monitoring. The Australian populations are relatively small and their distri- bution is limited to remote areas in the northern part of the country. Previous global genetic stud- ies of olive ridley populations showed that the Australian breeding population at the McCluer Group of islands, Northern Territory, is genetically distinct from other olive ridley populations breeding in the Indo-Pacific. However, nothing is known about the genetic stock structure among Australian olive ridley rookeries found across northern Australia. High predation of eggs by feral pigs, dogs and monitor lizards Varanus spp. is believed to have severely impacted the number of nesting females at some rookeries. Of particular concern is the small nesting population on the western Cape York Peninsula, and without immediate conservation action this population could face extinction. The results presented here establish that there are at least 2 independent manage- ment units (stocks) of olive ridley turtles nesting in Australia and emphasise the importance of conserving the genetically distinct small breeding population nesting along the western Cape York Peninsula. In addition, results from 44 turtles caught in ghost nets across the Gulf of Carpen- taria revealed that 45% of the haplotypes (32% of all ghost net samples) had not been observed at any rookery in Australia or SE Asia. This research highlights the need for better information on olive ridley population structure in the region and for urgent conservation action for the western Cape York population.

Neonate survival en handled broods of the Olive Ridley Turtle Lepidochelys olivacea (Testudines: Cheloniidae) in “El Verde”, Sinaloa, Mexico

We worked in the protective and conservation area of the Olive Ridley Turtle Lepidochelys olivacea in the beaches of Estero Verde, Sinaloa, Mexico (2004 season). The position in the beach does not affect survival. We found nests until the preferential nesting site located at the beginning of the second sandy berm in a zone free of vegetation; and the latter presented a slight increase in survival. Specimens handled for 2-5 hours survived less (R2=0,82). KEY WORDSIncidence of turtles, management, survival, protected area, conservation.

Estructura de tallas de tortuga pico de loro Lepidochelys olivacea (Testudines: Cheloniidae) en Tumbes, Perú

In this paper we analyzed the size structure of Olive Ridley turtle Lepidochelys olivacea, from individuals stranded and incidentally caught in beaches of Tumbes, Peru (3o38’9.5”S – 80o36’2.48”W; 3o57’21.3”S – 80o57’45.72”W), since November 2006 to October 2011. The study area was divided into three contiguous areas, which were limited by the most active streams (Bocapan, El Rubio and Pena Negra). There were 39 individuals (74.4% stranded and 25.6% caught incidentally), with sizes ranged from 45 to 75 cm CCL (62.5±5.7 cm CCL). 64.1% was considered sub-adult individuals (<65 cm CCL, n= 25). Spatially the largest number of records occurred in zones 3 and 2, in which percentages above 60% were considered sub-adults, while in zone 1, 83% was adult. Temporarily in the rainy season were registered the majority of the observations (59%), in which 78.3% of specimens was sub-adult, being higher than in the dry season (43.8%). Sizes showed significant differences between zones and climatic seasons. It was confirmed the latitudinal distribution pattern by apparent maturity stages (more adults in the north). Adults’ occurrences suggest that Tumbes coast would be a potential nesting area of L. olivacea, most likely to oviposit in dry season, it which is supported by recent nesting events.

The effect of incubation temperature on hatchling quality in the olive ridley turtle, Lepidochelys olivacea, from Alas Purwo National Park, East Java, Indonesia: implications for hatchery management

Nest protection through egg relocation from natural nests into protected hatcheries is a common practice used at rookeries around the world to increase hatchling recruitment into sea turtle populations. However, rarely have the impacts of this practice on hatchling recruitment and quality been assessed. This study investigated the influences of the thermal nest environment of olive ridley turtles Lepidochelys olivacea on emergence success and quality of hatchlings of hatchery nests in Alas Purwo National Park, East Java, Indonesia (2009 and 2010 nesting seasons). Nest temperatures above 34 °C for at least 3 consecutive days during incubation in the hatchery resulted in decreases in emergence success and locomotor performance of hatchlings. The use of the hatchery is recommended due to extremely high predation rate of nests left on the beach; however, altering hatchery management practice by spacing nests one meter apart and providing shade should improve hatchery outcomes now and into the future.

Olive ridley turtle Lepidochelys olivacea in French Guiana: back from the brink of regional extirpation?

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.

Satellite tracking reveals unusual diving characteristics for a marine reptile, the olive ridley turtle Lepidochelys olivacea

The movements, diving behaviour and thermal environment occupied by 4 adult female olive ridley turtles Lepidochelys olivacea in northern Australia were determined through satellite telemetry. Patterns of behaviour recorded were rather unusual compared to other sea turtles in that dives were mainly deep, largely benthic and exceptionally long (>2 h) in some cases, characteristics typical of over-wintering turtles in colder environments. One individual occupied shallow coastal for- aging zones, while the others foraged far from land (probably on the seabed) in relatively deep water (>100 m). Individuals performed long dives (frequently >100 min), but from the short post-dive inter- vals we suggest that these dives were mainly aerobic. Maximum dive depth recorded was 200 ± 20 m (mean maximum depths ranged from 20.1 to 46.7 m across individuals; n = 17 328 dives in total; depths ≥3 m were considered 'dives') and the maximum duration was 200 ± 20 min (mean durations ranged from 24.5 to 48.0 min across individuals). Temperature profiles indicate that turtles experi- enced temperatures ranging from 23 to 29°C at the surface, with the lowest temperature recorded (18.7°C) at a depth of 98 m. Only 6.9% of the dives were in water <20°C. From time-allocation at depth (TAD) scores, we demonstrated that many dives reaching the known or inferred sea bottom were U-shaped, but there was no apparent diel signal in dive depth. This suggests that many benthic dives were not associated exclusively with resting behaviour and likely had a foraging component as well. The ability to perform long benthic dives allows this species to exploit deeper benthic environ- ments in addition to the shallow coastal areas more generally occupied by adult hard-shelled sea tur- tles (e.g. green and hawksbill turtles). Deep benthic dives also occur in certain marine mammals (e.g. narwhals) and sea birds (e.g. rockhopper penguins) and therefore seem to be a general foraging strategy exploited by animals that can perform long dives.

At-sea density and abundance estimates of the olive ridley turtle Lepidochelys olivacea in the eastern tropical Pacific

ABSTRACT: The first at-sea estimates of density and abundance of the olive ridley turtle Lepi-dochelys olivacea in the eastern tropical Pacific (ETP) were produced from shipboard line-transectdata. Multi-ship surveys were conducted in 1992, 1998, 1999, 2000, 2003, and 2006 in the areadefined by 5°N, 120°W, and 25°N and the coastline of Mexico and Central America. Sighting data ofolive ridleys were stratified by survey effort and sighting conditions, thereby reducing potentialbiases from heterogeneous observation conditions. Dive data from satellite telemetry studies wereused to correct for the proportion of turtles that were submerged and unavailable for detection dur-ing the surveys. A weighted average of the 5 by-year estimates (1998 to 2006) was 1.39 million (coef-ficient of variation, CV = 19.7%; approximate 95% CI: 1.15 to 1.62 million). Our findings are consis-tent with the dramatic increases of olive ridley nesting populations that have been reported over thepast decade for beaches in the ETP.KEY WORDS: Line transect · DISTANCE · Endangered species