Giant Devil Rays in the North-Western Mediterranean Sea
Giuseppe Notarbartolo di Sciara, Tethys Research Institute

Dataset credit

Tethys Research Institute

Contacts

RoleNameOrganization 
Primary contact Giuseppe Notarbartolo di Sciara Tethys Research Institute
Data entry Ei Fujioka Duke University

Citation

Abstract

The giant devil ray Mobula mobular, the only Mediterranean mobulid, is subject to mortality caused by directed and accidental captures in fisheries throughout the region. Whilst the combination of human impacts, limited range and a low reproductive potential is not inconsistent with its endangered listing, there are insufficient data to enable a quantitative assessment of trends. Without this, it is difficult to assess and prioritise threats and develop effective conservation actions. Using results from aerial surveys conducted between 2009 and 2014 over the Ligurian, Corsican, Sardinian, northern and central Tyrrhenian seas (626,228 km2), this study provides the first quantitative information on giant devil ray abundance and habitat choice in the western Mediterranean. Devil rays were observed in all seasons except winter, with their estimated abundance in the study area peaking in summer.
The overall uncorrected mean density in the study area during summer was estimated at 0.0257 individuals km-2 (range: 0.017–0.044), resulting in a total abundance estimate of 6,092 (12.7%CV) individuals at the surface; once corrected for availability bias, this estimate indicates a summer presence of >12,700 devil rays in the study area. Rays were mostly observed alone even if occasionally, larger aggregations up to a maximum of 18 individuals were observed. Although observed throughout the study area, spatial modelling identified their preferred habitat to be over a broad strip connecting the Tuscan Archipelago to Eastern Sardinia, over a wide range of water depths ranging from 10 to 2000m. The observed seasonal changes in giant devil ray distribution in this study, combined with similar evidence from other areas in the Mediterranean, support the hypothesis that the species
undertakes latitudinal migrations across the region, taking advantage of highly productive waters in the north during summer, and warmer southern waters during winter.

Purpose

N/A

Supplemental information

Some records do not have time part.

References

Attributes

Overview

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

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 in dataset provided

Attribute (table column)Description
oidUnique ID number (generated by OBIS-SEAMAP)
sectorSub areas
dateDate of the sighting
timeTime of the sighting (local time zone)
latLatitude in decimal degree
longLongitude in decimal degree
group_sizeGroup size
speciesSpecies name
sp_tsnTaxonomic Serial Number added by OBIS-SEAMAP
geomGeometry field added by OBIS-SEAMAP
OBIS-SEAMAP ID1370
Seabirds0
Marine mammals0
Sea turtles0
Rays and sharks298
Other species0
Non spatial0
Non species0
Total298
Date, Begin2009-07-21
Date, End2013-08-07
Temporal prec.111111
Latitude36.27 - 44.30
Longitude5.85 - 19.00
Coord. prec.6 decimal digits
PlatformPlane
Data typeAnimal sighting
EffortN/A
Registered2016-04-08
Updated2016-04-11
StatusPublished
Sharing policy CC-BY-NC (Minimum)
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