Marine turtle sightings, strandings and captures in French waters 1990-2003

Matthew Witt, University of Exeter

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.

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 is from Witt et al. 2007; data included in this dataset are a subset of data presented in Witt et al. 2007.

References:

Duguy, R. 1990. Observations de tortues marines en 1990 (Manche et Atlantique). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 7:1053–1057.

Duguy, R. 1992. Observations de tortues marines en 1991 (Atlantique). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 8:35–37.

Duguy, R. 1993. Observations de tortues marines en 1992 (Atlantique). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 8:129–131.

Duguy, R. 1994. Observations de tortues marines en 1993 (Atlantique). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 8:235–238.

Duguy, R. 1995. Observations de tortues marines en 1994 (Atlantique). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 8:403–406.

Duguy, R. 1996. Observations de tortues marines en 1995 (Atlantique). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 8:505–513.

Duguy, R. 2004. Observations de tortues marines en 2003 (cotes Atlantiques). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 9:361–366.

Duguy, R., P. Moriniere and A. Meunier. 1997a. Observations de tortues marines en 1997. Annales de la Societe des Sciences Naturelles de la Charente-Maritime 8:761–779.

Duguy, R., P. Moriniere and M.A. Spano. 1997b. Observations de tortues marines en 1996 (Atlantique). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 8:625–632.

Duguy, R., P. Moriniere and A. Meunier. 1999. Observations de tortues marines en 1998 (Atlantique). Annales de la Societe des Sciences Naturelles de la Charente-Maritime:911–924.

Duguy, R., P. Moriniere and A. Meunier. 2000. Observations de tortues marines en 1999. Annales de la Societe des Sciences Naturelles de la Charente-Maritime 8:1025–1034.

Duguy R, P. Moriniere and A. Meunier. 2001. Observations tortues marines en 2000 (Atlantique et Manche). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 9:17–25.

Duguy, R., P. Moriniere and A. Meunier. 2002. Observations de tortues marines en 2001 (Atlantique et Manche). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 9.

Duguy, R., P. Moriniere and A. Meunier. 2003. Observations de tortues marines en 2002 (Atlantique et Manche). Annales de la Societe des Sciences Naturelles de la Charente-Maritime 9:265–273.

Overview

This section explains attributes included in the original dataset. OBIS-SEAMAP restricts the attributes available to the public to date/time, lat/lon and species names/counts only. Should you need other attributes described here, you are encouraged to contact the data provider.

Attributes described below represent those in the original dataset provided by the provider.
Only minimum required attributes are visible and downloadable online. Other attributes may be obtained upon provider's permission.

Attributes in dataset

Attribute (table column)	Description
oid	Unique ID (generated by OBIS-SEAMAP)
sp_obs	Species observed
sp_tsn	Species ITIS TSN
statusen	definition not provided
statusfr	definition not provided
sightstran	definition not provided
day	Day of observation
month	Month of observation
year	Year of observation
obs_date	Date of observation
latitude	Latitude of observation
longitude	Longitude of observation
location	Description of location
scl	Straight carapace length (cm)
mass	Mass (kg)
obs_time	Time was not available so "00:00:00" was used
obs_count	Count was not available, so 1 was used
notes	Notes on when time and count was not available, so "00:00:00" and 1 were used, respectively
geom	definition not provided