Results and status, including trends (CI3 MT)

Results and Status, including trends (brief)   

This general overview reconfirms that most nesting sites of loggerheads are located in the eastern and central basins of the Mediterranean, in particular in Greece, Turkey, Cyprus and Libya, while all green turtle nesting sites are located in the eastern basin, primarily Turkey, Syria and Cyprus. The number of nests found at different sites is not just dependent on climate, but other factors, like predation, sand type/structure etc. Most research has been conducted on nesting beaches; consequently, detailed information about marine habitat use at developmental, foraging and wintering grounds and how these areas connect with one another and the overlap in use by multiple populations is still missing.

Results and Status, including trends (extended)        

Loggerhead sea turtles.

Nesting sites: Over 100 sites around the Mediterranean have scattered to stable (i.e. every year) nesting (Halpin et al., 2009; Kot et al. 2013; SWOT, 2006a, 2006b, 2008, 2009, 2010, 2011, 2012). Most sites are located in the eastern and central basins of the Mediterranean (Figure 5).

Figure 5
Figure 5: Map of the major loggerhead nesting sites in the Mediterranean (extracted from Casale & Margaritoulis), Black circles: >100 nests/year; white circles: 50-100 nests/year : Major nesting sites (>50 nests/year) of Loggerheads in the Mediterranean. 1 Lefkas; 2 Kotychi; 3 Zakynthos; 4 Kyparissia; 5 beaches adjacent to Kyparissia town; 6 Koroni; 7 Lakonikos Bay; 8 Bay of Chania; 9 Rethymno; 10 Bay of Messara; 11 Kos; 12 Dalyan; 13 Dalaman; 14 Fethiye; 15 Patara; 16 Kale; 17 Finike-Kumluca; 18 Cirali; 19 Belek; 20 Kizilot 21 Demirtas; 22 Anamur; 23 Gosku Delta; 24 Alagadi; 25 Morphou Bay; 26 Chrysochou; 27 Lara/Toxeftra; 28 Areash; 20 Al-Mteafla; 30 Al-Ghbeba; 31 Al-thalateen; 32 Al-Arbaeen. Country codes: AL Albania; DZ Algeria; BA Bosnia and Hersegovina; HR Croatia; CY Cyprus; EG Egypt; FR France; GR Greece; IL Israel; IT Italy; LB Lebanon; LY Libya; MT Malta; MC Monaco; ME Montenegro; MA Morocco; SI Slovenia; ES Spain; SY Syria; TN Tunisia; TR Turkey; Ad Adriatic; Ae Aegean; Al Alboran Sea; Io Ionian; L

Sporadic to regular nesting has been recorded in Cyprus, Egypt, Greece, Israel, Italy, Lebanon, Libya, Malta, Syria, Tunisia and Turkey (Margaritoulis et al. 2003; Casale & Margaritoulis 2010). Surveys have been conducted for tracks in Algeria (last surveyed 1980s), Croatia (last surveyed 1990s), France (last surveyed 1990s), Malta (last survey on 2015 through the LIFE+ MIGRATE project (LIFE11NAT/MT/1070)) Morocco (last surveyed 1980s) and Spain (last surveyed 1990s) (Margaritoulis et al. 2003; Casale & Margaritoulis 2010). Information on nesting has not been gathered for Albania, Montenegro, Monaco, Slovenia or Bosnia (Margaritoulis et al. 2003; Casale & Margaritoulis 2010). A recent IUCN analysissuggests that, when all Loggerhead nesting sites in the Mediterranean are considered together, the geographic distribution of loggerheads in the Mediterranean is broad, and is considered of Least Concern though conservation dependent, under current IUCN Red List criteria (Casale 2015).

Most nests are laid in Greece, Turkey, Cyprus and Libya (Margaritoulis 2003; Casale & Margaritoulis 2010; Almpanidou et al. 2016). An average of 7200 nests are made per year across all sites (Casale & Margaritoulis 2010), which are estimated to represent 2,280–2,787 females based on clutch frequency assumptions (Broderick et al. 2002). Greece and Turkey alone have more than 75% of the nesting in the Mediterranean; however, the smaller populations at other sites such as Libya and Cyprus are also of regional significance being at the edges of the species range (Demography Working Group, 2015). Of note, the beaches of the countries of North Africa have not been extensively surveyed, particularly Libya, so gaps on the numbers and distribution of nests still remain. Genetic analyses suggest low gene flow among groups of rookeries; thus, it is essential to preserve distinct genetic units (Carreras et al. 2006).

The number of nests held at different sites is not just dependent on climate, but other factors, like predation, sand type/structure etc. (Almpanidou et al. 2016). Thus, a recent study of all Mediterranean nesting sites showed that the climatic suitability of current stable sites will remain suitable in the future (Almpanidou et al. 2016). However, other factors may lead to the loss of these sites, such as sea level rise (e.g. Katselidis 2014). Furthermore, Almpanidou et al. (2016) showed that sites with sporadic nesting might be increasingly used, i.e. such sites might not be past sites that are infrequently used, but may reflect the exploratory nature of turtles to locate new alternative sites (Schofield et al. 2010a). Thus, it is worth ensuring that all current stable nesting sites are fully protected (with their use into the future being likely); however, it is also important to follow how the use of sporadic nesting sites changes over time, to detect new sites of importance in need of protection (Katselidis 2014; Almpanidou et al. 2016). 

Foraging (adult and developmental) and wintering sites: Most research has been conducted on nesting beaches; consequently, detailed information about marine habitat use at developmental, foraging and wintering grounds is still missing (Figure 6).

Figure 6
Figure 6: Foraging sites identified across the Mediterranean based on published papers (extracted from Schofield et al. 2013)

Discrete foraging sites frequented by male (black triangles) and female (grey triangles) loggerheads from Zakynthos (with some turtles frequenting more than one site). The foraging sites are indicated and numbered by open circles; orange circles = foraging sites overlapping or in close proximity to existing marine protected areas and/or national parks. Discrete foraging sites are arbitrary, and defined as a single site or group of overlapping sites that are separated from adjacent sites by a minimum distance of 36 km, which reflects the mean migration speed of loggerhead turtles (1.5 km h-1; Schofield et al., 2010) over a 24 h period. In addition, other known loggerhead (filled dark grey circles) and green turtle (filled light grey circles) foraging sites based on published datasets (Bentivegna, 2002; Margaritoulis et al., 2003; Broderick et al., 2007; Hochscheid et al., 2007; Casale et al., 2008). Note: solely juvenile foraging sites of the West Mediterranean have not been included here. The table below lists the different foraging sites, including the species, size class and genetic populations detected at these sites in various papers.

The way in which adult and newly hatched turtles disperse from breeding sites has been explored using a range of techniques in the Mediterranean, including genetics, stable isotope, satellite tracking, particle tracking and stable isotopes (e.g. Zbinden et al 2008, 2011; UNEP(DEPI)/MED. 2011; Schofield et al. 2013; Patel 2013; Luschi & Casale 2014; Casale & Patrizio 2014; Hays et al. 2014; Snape et al. 2016). These studies indicate that loggerheads probably forage throughout all oceanic and neritic marine areas of the west and east basins of the Mediterranean (Hays et al. 2014; Casale & Marianni 2014). Most satellite tracking studies have been conducted in Spain (of juvenile turtles), Italy (a mix of juvenile and adult turtles) and Greece (adult males and females) and Cyprus (adult females) (UNEP(DEPI)/MED. 2011; Casale & Patrizio 2014). Due to these biases, the results of tracking studies alone should be treated with caution.

Through combining studies using various techniques, loggerheads do not appea to be uniformly distributed (Clusa et al. 2014), with foraging in different sub basins affecting remigration rates, body size and fecundity (Zbinden et al. 2011; Cardona et al. 2014; Hays et al 2014). While most turtles that breed in the eastern basin tend to forage in the eastern and central areas, increasing numbers of satellite studies are showing that some individuals do disperse to and use the western basin too (Bentivegna 2002; Schofield et al. 2013; Patel 2013). The west Mediterranean primarily supports individuals from the Atlantic (Laurent et al. 1998; Carreras et al. 2006; Casale et al. 2008). Tracking studies of juvenile loggerheads in the western Mediterrnaean show that they are widely distributed throughout the entire region (UNEP(DEPI)/MED. 2011). As information on the distribution is not available on juvenile loggerheads in the central and east Mediterranean, it is likely that similarly ubiquitous distribution exists, but needs confirming (UNEP(DEPI)/MED. 2011).

The two most important neritic loggerhead foraging grounds for adults and juveniles appear to be the Adriatic Sea and the Tunisian Continental Shelf (including Gulf of Gabés) (Zbinden et al. 2010; Casale et al. 2012; Schofield et al. 2013; Snape et al. 2016). Important oceanic areas include the Alboran Sea, the Balearic Sea and different parts of the North African coasts, as well as the Sicily Channel. Large numbers of juvenile loggerheads have been documented in the south Adriatic too (Casale et al. 2010; Snape et al. 2016). Aerial and fishery bycatch data indicate that the highest density of turtles occur in the western basin Alboran Sea and Balearic islands, the Sicily Strait, the Ionian Sea, the north Adriatic, off Tunisia, Libya, Egypt and parts of the Aegean (Gómez de Segura et al. 2003, 2006; Cardona et al. 2005; Lauriano et al. 2011; Casale & Margaritoulis 2010). In Egypt, Bardawil Lake has been identified as an important foraging area for adult and juvenile loggerheads based on stranding records and tracking studies of turtles from Cyprus (Nada et al. 2013, Snape et al. 2016).

However, establishing the distribution of, even coastal, foraging sites has yet to be achieved. Certain sites, where high numbers of turtles of all size classes from different populations aggregate in confined areas, have been identified, such as Amvrakikos Bay, Greece (Rees & Margaritoulis 2008) and Drini Bay, Albania (White et al 2011). However, tracking studies also show that the foraging areas of individual turtles may extend from <10 km2 up to 1000 km2 in the open waters of the Adriatic and Gulf of Gabés (Schofield et al. 2013). Furthermore, knowledge of how foraging habitat differs between adult males and females, as well as how these sites overlap with juvenile developmental habitat remains limited across the various populations (Snape et al. in submission). Particle tracking has suggested that, within the Mediterranean, adults exhibit high fidelity to sites where they established use as juveniles (Hays et al. 2014).

Furthermore, various studies have shown that, while turtles exhibit high fidelity to certain sites (Schofield et al. 2010b), both juvenile and adult loggerheads use more than one foraging site (sometimes up to 5), spanning both neritic and oceanic sites, particularly in the Ionian and Adriatic (Casale et al. 2007, 2012; Schofield et al. 2013). Adults that forage in the Adriatic, tend to use sites seasonally, shifting to alternative sites in winter (Zbinden et al. 2011: Schofield et al. 2013), although some hibernate (Hoscheid et al. 2007). However, juveniles have also been documented shifting into the Adriatic in winter, suggesting that some sites may be used year-round by different components of loggerhead populations (Snape et al. in submission). The use of multiple sites and seasonal shifts in site use need to be documented to understand how different foraging, developmental and wintering sites are connected. In this way, groups of areas should be protected where connections are known to exist.

Green turtles.

Nesting sites: Most green turtle nests (99%) are laid in Turkey, Cyprus and Syria, with the remainder being found in Lebanon, Israel and Egypt (Figure 7; Kasparek et al. 2001; Casale & Margaritoulis 2010). An average of 1500 nests are documented each year (range 350 to 1750 nests), from which an annual nesting population of around 339–360 females has been estimated (Broderick et al. 2002), ranging from 115 to 580 females (Kasparek et al. 2001). The five key nesting beaches include: Akyatan, Samadağ, Kazanli (Turkey), Latakia (Syria) and Alagadi (northern Cyprus), with Ronnas Bay also being a priority area (Stokes et al. 2015). This allows the conservation effort of the nesting beaches for this species to be highly focused.

Figure 7
Figure 7: Map of the major green turtle nesting sites in the Mediterranean (extracted from Casale & Margaritoulis): Major nesting sites (>40 nests/year) of green turtles in the Mediterranean. 1 Alata; 2 Kazanli; 3 Akyatan; 4 Sugozu; 5 Samandag; 6 Latakia; 7 North Karpaz; 8 Alagadi; 9 Morphou Bay; 10 Lara/Toxeftra. Closed circles >100 nests/year; open circles 40-100 nests/year. Country symbols, see previous map.

Foraging (adult and developmental) and wintering sites: As with loggerheads, most information about green turtles is restricted to the nesting habitats, rather than developmental, foraging, and wintering habitats. Green turtles have been primarily documented foraging and wintering along the Levantine basin (Figure 8 and Table 1; Turkey, Syria, Cyprus, Lebanon, Israel, Egypt) (Broderick et al. 2007; Stokes et al. 2015). However, foraging areas have also been documented in Greece (particularly, Lakonikos Bay and Amvrakikos Bay; Margaritoulis & Teneketzis 2003) and along the north coast of Africa, primarily Libya and some sites in Tunisia (see Figure 8 and Table for published sources). Some turtles have been documented in the Adriatic Sea (Lazar et al. 2004) and around Italian waters (Bentivegna et al. 2011), with some records occurring in the western basin (see Figure 8 and Table for published sources). In addition, Broderick et al (2007) detected wintering behaviour for greens off of Libya, with high fidelity to the same sites across years; however, further documentation has not been recorded for the other populations or other areas of the Mediterranean. These wintering sites were detected based on a shift in location to deeper water from early November to March/April and reduced area use compared to summer months, which were assumed to be indicative of reduced activity during the colder months. Lakonikos Bay in Greece and Chrysochou Bay in southern Cyprus represent well documented foraging grounds of juvenile green turtles based on strandings and bycatch databases. Within Egypt, Bardawill Lake has been identified as an important foraging area for adult and juvenile green turtles based on stranding records and tracking studies of turtles from Cyprus (Nada et al. 2013). In Turkey, green turtles have been documented stranded in the Gulf of Iskenderun, and might represent foraging habitat, while juvenile green turtles have been confirmed inhabiting the coast along the Cukurova, with Samandag and Fethiye Bay also representing possible juvenile foraging grounds (see Casale & Margaritoulis 2010 for overview). Overall, the way in which the foraging grounds are distributed and the numbers and size classes that they support, or how frequently green turtles move among sites (i.e. connectivity), remains limited.

Table 1. Length of built-up coastline in Italy in 2006 (provided by Project EcAp-ICZM Italian Ministry of Environment/ISPRA)
Table 1 (extracted from Schofield et al. 2013a): Published literature used to identify overlap in foraging sites (A) based on tracking datasets and (B) based on genetic data. Foraging category, NO = neritic open sea; NC = neritic coastal. Thermal state, Avail = availability; Use = recorded use; Y-R = year round; S (Wi) = Seasonal (Winter); S (Su) = Seasonal (Summer); Unconf. = unconfirmed. Species, Log = loggerhead; Gre = Green; Gender/Ageclass, M = adult male; F = adult female; Juv = juveniles, with gender not differentiated. Breeding populations, ? = unconfirmed; Zak = Zakynthos, Greece; Kyp = Kyparissia, Greece; Cyp = Cyprus; Syr = Syria; T = Turkey; Lib = Libya; Tunis = Tunisia; Mess = Messina; Cal = Calabria; Is = Israel; It = Italy. Sources: 1 = current study; 2 = Casale et al., (2007, 2010); 3 = Zbinden et al., (2008, 2011); 4 = Margaritoulis et al., (2003); 5 = Bentivegna (2002); 6 = Broderick et al., (2007); 7 = Hochscheid et al., (2007); 8 = Echwikhi et al., (2010); 9 = Chaeib et al., (in press); 10