Ecology of marine turtles across the eastern Mediterranean and the Middle East
Rees, Alan Frederick
Date: 24 April 2013
Thesis or dissertation
Publisher
University of Exeter
Degree Title
PhD in Biological Sciences
Abstract
Marine turtles are wide-ranging, long-lived, iteroparous species of conservation
concern. From indirect threats, such as development at their breeding grounds and
negative fisheries interactions, to direct take of eggs meat and shells, they are
impacted at all stages of their life-cycle by the activities of Man. A better understanding
of ...
Marine turtles are wide-ranging, long-lived, iteroparous species of conservation
concern. From indirect threats, such as development at their breeding grounds and
negative fisheries interactions, to direct take of eggs meat and shells, they are
impacted at all stages of their life-cycle by the activities of Man. A better understanding
of their reproductive and spatial ecology together with knowledge of population status
can inform conservation and management actions for their protection. This thesis
presents a collection of chapters covering three species of marine turtle, from four
countries in two regions where major knowledge gaps existed on marine turtle biology
and ecology.
In Oman we identify plasticity in adult loggerhead turtle (Caretta caretta) internesting
behaviour combined with globally-atypical, predominantly oceanic habitat use and we
raise concerns over potential bias derived from temporally-restricted tracking studies.
Conversely, we show that adult female individuals of the principally oceanic olive ridley
turtle (Lepidochelys olivacea) remain in neritic waters outside of the breeding season,
with some local turtles unusually utilising the same location both during and after the
breeding period. We also show that green turtles (Chelonia mydas) nesting on Masirah
Island are long distance migrators, travelling 2000 km or more into the Red Sea.
Together with our tracking data for the other species in Oman we highlight the threat
that fisheries interaction, in a region with poor fisheries regulation, is likely to have on
these populations.
We describe the recent status of green turtle populations in Kuwait and Syria. In Kuwait
nesting habitats have recently been halved through development of one of the two
critical nesting areas and with the remaining nesting population estimated at no more
than 5 females per year. For Syria, we describe the discovery of a regionally important
nesting aggregation located south of Latakia city, with 30 individuals estimated nesting
in 2004. Using satellite telemetry we identify potentially important foraging locations for
individuals from both locations. Results from Syria further highlight the importance of
neritic habitats off north Africa for adult turtles in the Mediterranean and results from
Kuwait revealed the potential threat from the use of the unselective coastal fish traps
locally known as a ‘hadra’.
Lastly, in Greece we investigate the status of turtles in a neritic coastal habitat through
a boat-based mark-recapture study. Combining flipper tagging, satellite telemetry and
genetic research we verify that Amvrakikos Gulf hosts regionally important numbers of
3
loggerhead turtles (300 individuals identified from 67 days fieldwork) that establish
distinct home ranges and maintain long-term associations to the area. A male-biased
sex ratio was revealed in the area. These turtles are predominantly derived from local
breeding stocks, especially from Zakynthos Island, and we hypothesise that a
combination of environmental and biological factors specific to Zakynthos Island are
the cause of this bias.
The results presented here, generated from a range of techniques including field
surveys, satellite telemetry and genetic analysis, contribute to our knowledge of the
status of several under-reported or previously unknown sea turtle populations,
including evidence of their spatial footprint, and demonstrate the utility in adopting a
variety of methods to corroborate results on migrations and linkages at individual and
population levels.
Doctoral Theses
Doctoral College
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