We set out to determine the spatial and temporal trends for sightings, strandings and captures of hard-shell marine turtles in the northeast Atlantic from two recording schemes. One recording scheme (presented here) included marine turtle sightings, strandings and captures occurring in French waters that originated from annual sightings and strandings publications of Duguy and colleagues (Duguy 1990, 1992, 1993, 1994, 1995, 1996, 2004; Duguy et al. 1997a, b, 1999, 2000, 2001, 2002, 2003). Records presented in Duguy publications prior to 2001 contained location descriptions, providing no geographic coordinates with error estimates. Longitude and latitude positions for these events were estimated to be the closest coastal point to the descriptive location.
Duguy publications, 2001 onwards, were accompanied by maps displaying the approximate location of sightings and strandings events. These maps were digitized and georeferenced and coordinate positions determined for all appropriate records. Georefenced hard-shell turtle (Lk and Cc) capture/sighting/stranding records from the papers of Duguy for France 1990-2003 (featured in Witt et al. 2007) only includes records that could have coordinates derived from their locational descriptions.
The second recording scheme used were records of sightings and strandings of marine turtles in the British Isles obtained from the TURTLE database operated by Marine Environmental Monitoring. Data from the TURTLE database were submitted to EurOBIS and can be viewed on OBIS-SEAMAP: Marine Turtles. Abstract
We present data spanning approximately 100 years regarding the spatial and temporal occurrence of marine turtle sightings and strandings in the northeast Atlantic from two public recording schemes and demonstrate potential signals of changing population status. Records of loggerhead (n = 317) and Kemp’s ridley (n = 44) turtles occurring on the European continental shelf were most prevalent during the autumn and winter, when waters were coolest. In contrast, endothermic leatherback turtles (n = 1,668) were most common during the summer. Analysis of the spatial distribution of hard-shell marine turtle sightings and strandings highlights a pattern of decreasing records with increasing latitude. The spatial distribution of sighting and stranding records indicates that arrival in waters of the European continental shelf is most likely driven by North Atlantic current systems. Future patterns of spatial-temporal distribution, gathered from the periphery of juvenile marine turtles habitat range, may allow for a broader assessment of the future impacts of global climate change on species range and population size.