Increase in stranding levels reveals important new foraging ground for Chelonia Mydas off Cyprus Linda Stokes1, David Stokes1, Kostis Grimanis2, J D Pantis3 1 Episkopi Turtlewatch ,Western British Sovereign Base Area, Cyprus 2 MEDASSET, The Mediterranean Association to Save the Sea Turtles 3 Department of Ecology, School of Biology, Aristotle University of Thessaloniki
Episkopi Bay coast line of approximate total length 15km
Strandings
Graph showing verified strandings 2005-2011
Introduction
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Episkopi bay is on the south coast of Cyprus in the British held Sovereign Base Area. It has a beach length of approximately 15km and is a minor nesting area for Caretta Caretta and Chelonia Mydas. The bay also borders Akrotiri nesting beaches which are approximately 6km long and have more significant nesting. The average annual nesting level of the combined areas is 45-60 nests. The ratio of nesting Chelonia Mydas to Caretta Caretta is approximately 1 to 10. Prior to 2008 strandings at Episkopi were rare and mostly comprised severely decomposed Caretta Caretta. Consequently it was assumed that turtle presence in the bay: Was restricted to mating and nesting seasons; Mainly consisted of Caretta Caretta, and Clustered near Akrotiri beaches and not near those at Episkopi.
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25
20 Loggerhead Green
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Since 2008 there has been a dramatic increase in the number of strandings at Episkopi beaches and also a change in their composition. The majority of strandings are now "freshly killed" or "moderately decomposed". From July 2008 onwards stranding figures have been dominated by Chelonia Mydas. The remainder of the strandings have been of adult Caretta Caretta. Current flows in the area are generally from west to east and therefore the turtles are unlikely to have been near Akrotiri beaches when they died.
2005
2006
2007
2008
2009
2010
Consistent stranding monitoring methods have been applied throughout the period 2005 to 2011. The sudden increase in strandings from 2008 coincided with an observed change in fishing practices on the part of local artisanal fishermen. Necropsies performed in 2009 on 11 turtles confirmed that all had died as a result of fishing interaction and at least 7 of these had died close to the beach where they were found. Approximately 40% of all strandings since 2008 have been deliberately killed by a blow to the head. Many have ligature marks and torn flippers consistent with net entrapment.
2011 to date
Two of three strandings recorded in Zapalo Bay 23 August 2009 immediately following the removal of a fishing net from the bay.
One of seven strandings at Curium Beach in 2011
Concerned by the stranding levels and the lack of protective measures in the area a decision was taken to investigate whether Episkopi Bay beaches did in fact have a significant local turtle population. In the event of a positive result an investigation of the species composition of the population would also be pursued. Since 5 May 2010 20 aerial surveys of the Episkopi Bay area have been conducted. Flight data to date shows a mean surface count of 57 turtles. The range is from 27 to 115 with a standard deviation of 22. On eight occasions since 1 December 2010 the aerial survey has been co-ordinated with a boat survey. The boat crew has been directed to the centre of clusters located by the aerial survey team and recorded the species type and size seen in the clusters. The percentage of green turtles recorded ranges from 50% to 100%. In 2010 three boat surveys examined the underwater habitat in the main cluster areas identified by previous aerial surveys. These found the sea bed in the areas to be covered with cymodocea nodosa. In 2010 and 2011 the survey work has been supplemented by the distribution of turtle "sighting" forms amongst local beach outlets. In 2010 data from the forms suggested an average of 40 sightings per month in shallow water during the period May to August. Species identification was unreliable but sightings indicated a mix of adult and juvenile turtles present in the area.
Chelonia mydas strandings 2008-2011 by CCL
16, 23%
25, 36% 0-40cm
41-60cm 29, 41%
Supplemental to this it was noted that a satellite tracked adult female green turtle (86900) which was part of the 2010 Marine Turtle Conservation Project in Northern Cyprus moved into the Episkopi Bay area following nesting. It could be seen that she remained in the area until the end of August 2011 after which time transmissions ceased.
Aerial surveys
60+cm
Strandings include both juvenile and adult turtles and occur on a year round basis. The majority may be classed as “fresh dead” or “moderately decomposed” in accordance with STSSN guidelines. There were no strandings 1 January 2011 to 22 May 2011. This period coincided with the absence of fishing vessels in the Episkopi bay area due to the silting up of the local harbour. Fishing did take place during this period in areas to the south and west of Episkopi beaches. In general throughout the year no strandings occurred during periods when the local harbour was not in use.
Current flows
Twenty aerial surveys were conducted in a 140 CESSNA light aircraft with two observers 120 and a dedicated data recorder. The surveys aimed to cover the Akrotiri and Episkopi 100 coastlines to a distance 3km offshore. The 80 pilot flew a zig zag pattern with a 30 de60 Turtle count gree angle at altitudes ranging between 40 240m and 360m. On four occasions the 20 south and east areas of Akrotiri were not covered because of military restrictions. 0 GPS recordings were used to eliminate possible double counts. Bad weather and aircraft availability restricted the ability to conduct surveys in some months. Species identification was not always possible from the air although in general juvenile greens appeared to predominate at the surface. Wherever possible surveys were conducted in Force 1 conditions. In winds higher than Force 2 surface ripples obscured sightings. Turtle count
Map of survey 20 September 2011 Points marked indicate the presence of turtle clusters. Turtles were spotted in the same general area during each survey flight. Out of the main mating and nesting season the largest clusters were seen in the eastern section of the bay. During peak nesting and mating periods the main concentrations were focused off beaches in the area marked “Episkopi Bay”.
Historical flow rate data available via the online “Cyprus coastal ocean forecasting and observing system”a was used in order to estimate the maximum in water Map showing 11.7 km radius from the two main distance that strandings in 2010 and 2011 might stranding points at Tunnel and Curium Beaches. have travelled prior to discovery. All 37 cases classed as fresh or moderately decomposed were examined. To be conservative fresh strandings were assumed to have drifted for one day at sea and moderately decomposed for two. The average daily flow rate on the preceding day(s) was then examined . The findings suggested that the maximum possible distance travelled in water prior to recovery was on average 11.7 km.
a
http://www.oceanography.ucy.ac.cy/cycofos/bulletin.html
Summary Episkopi has a relatively high chelonia mydas stranding level for a 15km coastline length 37 out of 43 strandings in 2010 and 2011 were freshly killed or had suffered only moderate decomposition Analysis of current flows in the periods preceding these 37 strandings suggests that the average maximum time each spent drifting at sea was 11.7km. 20 aerial surveys across 2010 and 2011 produced an average surface turtle count of 57 and turtles were present throughout the year. Information taken from sighting forms provides corroborating evidence of this. The area corresponding to an 11.7km radius from the two main stranding points coincides with the area where turtle sightings were recorded from the air. Boat surveys directed to the centres of observed clusters on 8 occasions recorded between 50-100% of turtles sighted on each occasion as green. Cymodocea nodosa was observed growing in shallow water offshore from Episkopi beaches. Stranding levels dropped significantly in periods when the Episkopi Bay fishing harbour was unusable and when military exercises restricted fishing in the bay.
Conclusions Evidence gathered to date suggests that there is a year round foraging population of green turtles in Episkopi Bay which requires protection. This population appears to be predominantly juvenile but does also Acknowledgements: We would like to thank Project AWARE International Foundation for grant support, and the following for include adults. Our aim is to refine and extend our survey work to establish a minimum population estimate their active involvement in this project: Ross Chapman, Pete Ring and RAF Akrotiri Flying Club, Lemfor the area and also its probable composition. Academics from Exeter University have declared an interest mings Watersports Club, Pete Hammond and all MTW Staff at Tunnel Beach, Inter Services Yacht Club at in working with us on this and as part of a wider project. We are now seeking financial backing to enable us Tunnel Beach, Curium Beach Lifeguards, Kingsman Cove Staff at Tunnel Beach and all volunteers past to complete the necessary fieldwork. and present at Episkopi Turtlewatch.