Four new records of stranded Kemp’s ridley turtle Lepidochelys kempii in the NW Iberian Peninsula
© The Author(s) 2016
Received: 2 August 2016
Accepted: 3 August 2016
Published: 31 August 2016
The critically endangered Kemp’s ridley turtle (Lepidochelys kempii) has a reduced distribution range concentrated in the Gulf of Mexico and only a few pelagic stage juveniles occasionally strand on European coasts. In the study area only three individuals have been recorded previously, most recently in 2001.
Four new records of Kemp’s ridley turtle are reported from the northwestern Iberian Peninsula in 2014. All of them were juvenile with a maximum straight carapace length of 26.8 cm. Two of them were found alive, but died on the first two days at the rehabilitation centres. The largest individual stranded in November presented signs of incidental capture in fishing gears.
The four records in just one year are a significant increase compared to previous data for the species in this area, and the data obtained contribute to the local knowledge on species phenology, size, distribution and threats.
KeywordsKemp’s ridley turtle Lepidochelys kempii Iberian Peninsula Distribution Sea turtle Strandings
In spite of a recent increase in population (Márquez et al. 2005) the Kemp's ridley turtle Lepidochelys kempii (Garman 1880) is considered the most threatened sea turtle species in the world, being categorized as critically endangered by the International Union for Conservation of Nature (IUCN) (Marine Turtle Specialist Group 1996). The Kemp's ridley turtle has a small, restricted geographic range compared to other sea turtles species (Zug et al. 1997). The nesting areas of this species are mainly located in the Mexican coast of the Gulf of Mexico (Márquez, 1990; Bowen et al. 1994) with some secondary isolated rookeries in Texas, Florida, South Carolina and North Carolina (Meylan et al. 1990; Bowen et al. 1994; Johnson et al. 1999).
Adult and immature Kemp’s ridley occur year-round in the Gulf of México, and juveniles are found at sea in the northwestern Atlantic Ocean as far as Nova Scotia and Canada (National Marine Fisheries Services US, Service FaW and SEMARNAT 2011). Occasionally some small turtles are also known to drift into European waters during the winter months (Brongersma 1972; Márquez 1994; Witt et al. 2007). There are several documented records showing the presence of Kemp’s ridley turtle in the waters around Azores (Brongersma 1972; Bolton and Martins 1990), Madeira (Brongersma 1972), British Islands and France (Brongersma 1972; Witt et al. 2007; Penrose and Gander, 2015) and in the Mediterranean Sea (Brongersma and Carr 1983; Tomás et al. 2003; Oliver and Pigno 2005; Tomás and Raga 2008; Insacco and Spadola 2010; Carreras et al. 2014).
In the NW Iberian Peninsula, previous documented records included only two individuals in the coast of Galicia (Spain), the most recently in 1998 (Fernández 1988; Faraldo and Galán 1999), and one individual in Portugal in 2001 (Dellinger 2008).
The present study provides a new report on the presence of and an increase in the records of Kemp’s ridley turtles in the waters around the NW Iberian Peninsula within a short time of ten months. Our work also contributes to the knowledge of the distribution of this species in the north-eastern Atlantic and provide insights to the main threats in the area to contribute to conservation efforts of this species in international waters.
Data collection and analysis
In the study area, two stranding networks are established: Coordinadora para o Estudo dos Mamíferos Mariños (CEMMA) in Galicia (NW of Spain) and Sociedade Portuguesa de Vida Selvagem (SPVS) in Portugal, since 1990 and 2000, respectively. These strandings networks record turtles and marine mammals stranded on the beaches, collect samples for Galician and Portuguese Marine Animal Tissue Banks and recover injured individuals for rehabilitation. They are coordinated via a 24 h telephone hotline.
Turtles were moved by the strandings networks mobile units to rehabilitation installations of CEMMA and SPVS to proceed with the veterinary examination and rehabilitation of the two individuals found alive and to carry out the necropsy of the dead ones following detailed protocols (Sociedad Española de Cetáceos 1999; Wyneken 2001). Turtles were measured (total length [TL]; straight carapace length [SCL]; curved carapace length [CCL]; straight carapace width [SCW] and curved carapace width [CCW] according to Bolten 1999), weighed, identified to species level, and the likely cause of death determined based on a complete external and internal examination. In cases when there was evidence of multiple lesions, the most severe and recent was assigned as the primary cause of stranding.
Biometry and geographic data of the four new records of stranded Kemp's ridley turtle in the Iberian Peninsula
Viñó Beach, Cangas do Morrazo, Spain
Boca do Río, Carnota, Spain
Tocha Beach, Cantanhede, Portugal
Gala Beach, Figueira da Foz, Portugal
Alive (died on first day)
Alive (died on second day)
The four turtles were juveniles with a SCL of between 19.5 and 26.8 cm, so according to published growth models derived from skeletonchronological studies in relation with the carapace length (Chaloupka and Zug, 1997; Zug et al. 1997), they had an estimated age of 2 years for the first three individuals and nearly 3 years for the fourth turtle. The time of year in which they stranded is consistent with previous records of the species found stranded on the European continental coasts, that are more usually found during the autumn and winter (Brongersma 1972; Witt et al. 2007). Goose barnacles found on the first and third turtles are commonly attached to floating objects and when they are found on dead or weak turtles that indicates that they spent a long period floating at the water’s surface (De Loreto and Bondioli, 2008), and that is likely associated with a chronic condition such as poor nutrition, chronic infections, parasitic diseases, immune deficiency or a combination of some or all of these causes (Deem et al. 2009).
In the NW Iberian Peninsula, and especially during winter, the seawater temperature is low, sometimes below 10 °C. The average sea surface temperature during the first three stranding events (February and first week in March) was around 12 °C (Feldman and McClain 2014). This low temperature could have been sufficient to affect the sea turtles physiology leading to cold-stunning events, in which turtles become lethargic and float at the water’s surface and, as a result, they may be unable to swim or feed (Schwartz 1978). Therefore, lack of feeding due to the low seawater temperature could explain the large weight differences up to 38 % (0.99 kg and 1.37 kg) between the two individuals that had similar lengths to those found alive in February and March (Table 1). In the case of the turtle stranded in November in Portugal, sea temperature was around 18 °C and therefore cold stunning event is unlikely to explain this turtle stranding. Considering the necropsy findings, this individual was probably a victim of incidental capture by fisheries. Interactions with coastal fisheries, especially interactions with gill or trammel net fisheries, represents an important anthropogenic threat to other sea turtle species (loggerhead Caretta caretta and leatherback Dermochelys coriacea) in the Portuguese continental coast (Nicolau et al. 2014).
Four new records in one year are a significant increase compared to previous data for the species in this area. In UK and Republic of Ireland an increase in the stranded Kemp's ridley turtle has also been reported in 2014 with 7 stranded turtles, while in the previous ten year period 2004–2013 the average rate was just 1 stranded individual (Penrose and Gander, 2015). It will be important to pay attention to the occurrence of the species in the next years in the European coasts to find out whether the 2014 numbers are isolated findings or whether they indicate a trend.
Curved carapace length
Curved carapace width
Coordinadora para o Estudo dos Mamíferos Mariños
Internation Union for Conservation of Nature
Straight carapace length
Straight carapace width
Sociedade Portuguesa de Vida Selvagem
We thank the staff of Dirección Xeral de Conservación da Natureza that found the two animals at the Galician beaches and took care of the alive one in the first hours. We also thank Juan Ignacio Díaz for helping with the field work and Ángela Llavona and Marisa Ferreira for their comments and suggestions during the writing of this note. The Quiaios Marine Animal Rehabilitation Centre provided technical support for the turtle found in Portugal. We are very grateful to the anonymous reviewers for their very useful comments that improved this note.
PC is supported by a research grant BI/UI88/7056/2014, AL is supported by a postdoctoral grant SFRH/BPD/82407/2011 and LN is supported by PhD grant SFRH/BD/51416/2011 both from the Portuguese Foundation for Science and Technology of the Portuguese Ministry of Science and Education. The Galician stranding network is supported by the regional government Xunta de Galicia, cofinanced with European Regional Development Funds (ERDF/FEDER).
PC, LN and AL wrote the manuscript. PC and LN participated in the field data collection and AL prepared the figures. All authors approved the final manuscript.
The authors declare that they have no competing interests.
Ethics approval and consent to participate
For the stranded animal management and the collection of biological samples all the legal permits were provided by the environmental administrations of Portugal and Galicia (Spain).
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