‘Shell-ebrations’, it’s World sea turtle day (16^th June 2019), the day of Dr. Archie Carr’s birthday, who is considered widely to be ‘the father of sea-turtle biology’. As an American herpetologist, ecologist, and a pioneering conservationist, Dr. Carr focused his career on sea-turtle research, during a time in which little was known about their biology (1959-1987). Currently, 50 years later, nearly half (45%) of the world’s sea turtle populations are threatened with extinction, according to the International Union for Conservation of Nature (IUCN); therefore, it has never been more important to keep Dr. Carr’s legacy alive to study, protect and conserve these species.

Life-history traits of sea turtles in the Mediterranean

To date, four species of sea turtle have been recorded in the Mediterranean (Table 1), including: loggerhead (Caretta caretta), leatherback (Dermochelys coriacea), green (Chelonia mydas) and hawksbill turtle (Eretmochelys imbricata; Panagopoulos et al., 2003; Casale et al., 2018). Each species has been classified as threatened by extinction on a global scale by the IUCN:

The following information, unless cited otherwise, has been taken from: www.IUCN.org, www.Medasset.org, and www.conserveturtles.org. Sea turtles have a varied diet, ranging from molluscs (e.g. octopuses, squids, and snails), corals, tunicates (sea squirts), crustaceans (e.g. crabs), sea urchins, sponges, jellyfish, seaweeds and seagrasses. Adult loggerheads are mainly carnivorous, adult green turtles are herbivorous and fully-grown leatherbacks and hawksbills are omnivorous. Loggerheads are the smallest species reaching 90 cm when fully grown, followed by hawksbills at 114 cm, while greens reach 150 cm, and leatherbacks are the largest, potentially growing to 175 cm. Hawksbill sea turtles perform maximum dives to 91 m (Blumenthal et al., 2009) and loggerheads have been recorded diving to a maximum of 110 m, green turtles to 233 m, and leatherbacks can reach depths of over 1000 m. Throughout their lives, sea turtles are naturally predated upon by different animals: Eggs can be dug up and consumed by foxes, lizards, jackals, and weasels, while hatchlings can be eaten by gulls, crabs, lizards, snakes, or cormorants, and even adults can be caught by large fish, sharks and occasionally seals. Currently, loggerheads and green sea turtles use more than 50 nesting sites across the Mediterranean, while leatherbacks and hawksbill sea turtles do enter the Mediterranean Sea to feed, but no nesting has been documented yet.

A closer look at loggerhead turtles (Caretta caretta)

A fundamental element of a species’ survivability is its genetic diversity, the more diverse a species is the more it can withstand changes in the environment (Allendorf, 1986; Lande, 1988). Tolve et al. (2018) completed analysis on mitochondrial DNA (Deoxyribonucleic acid; building blocks of complex cells that are housed in the mitochondrion of a cell which is ultimately the powerhouse of metabolism in complex cells) for 488 stranded or incidentally-captured loggerhead turtles across the Adriatic Sea. No significant genetic divergence between locations was observed; however, Greek and Crete populations provided the most abundant contributions to the Adriatic-mixed stock. Contrastingly, Bertuccio et al. (2019) found a high Libyan contribution to the Adriatic Sea, conducting similar analysis on 93 loggerhead turtles. Interestingly, five distinct haplotypes (term used to describe equivalent of a genotype for mitochondrial DNA) were documented, with two being endemic (found nowhere else) to the Mediterranean rookeries, suggesting the Mediterranean populations had derived from their north Atlantic conspecifics; however, data were subject to bias due to low sample size and a higher frequency of samples taken from Libya. Significant differences in physiological adaptations between the north Atlantic and Mediterranean populations have also been suggested by Marn et al. (2019). These studies highlighting life-history traits, ecology, population genetics, and evolutionary history are vital in the conservation of this species.

Threats & Conservation

Globally, threats facing sea turtles range from climate change, coastal development, light pollution, bycatch, sea litter, to intentional killing (Dobbs, 2001; Casale, 2010; Lutcavage et al., 2017; Arreola and Fulton, 2018; Casale et al., 2018; Delgado, 2018). Potential effects of climate change may affect sea turtles at different life-history stages from flooded nests due to rising sea levels (Daniels et al., 1993; Fuentes et al., 2010), to varying temperatures leading to skewed sex-ratios (Laloë et al., 2016; Bókony et al., 2019). Sex is determined by overall temperature during egg development, with cooler nests (<28 °C) producing males and warmer nests (>28 °C) producing females (Patel et al., 2016; Sandoval et al., 2017; Santos et al., 2017). Artificial lights (i.e. street lights, city light pollution) can disorientate hatchlings on their way out to sea (Lohmann et al., 2017; Celano et al., 2018) and disturb adults, emerging onto beaches to lay eggs (Lutcavage et al., 2017; Hu et al., 2018). Unintentional capture by fisheries (bycatch) is a serious issue facing all marine megafauna species (Reeves et al., 2013; Lewison et al., 2014; ICES CIEM, 2016; Hamilton and Baker, 2019) and it has been estimated that ca. 132,000 sea turtles are captured annually as bycatch in the Mediterranean causing ca. 44,000 deaths every year (Casale and Heppell, 2016).

Efforts to monitor, protect, and restore environments and individual sea turtles are being made across the Mediterranean. Loggerheads are the most common sea turtle species in the Mediterranean and an emblematic species to Greek seas. As such, they are widely protected by law (Mazaris et al., 2017; Casale et al., 2018). In particular their nesting site on Sekania is legally designated an area of absolute protection (Presidential Decree 966/1999), with only scientific research allowed in the National Marine Park of Zakynthos (Katselidis et al., 2013; Casale et al., 2018). In Greece, sea turtles use beaches on Zakynthos, Kyparissia, Lakonikos, Rethymno, Chania, Messenia, and Koroni throughout May–August to lay their eggs, before hatchlings appear from July–October, making their break for the ocean (Casale et al., 2018; Hatase and Omuta, 2018; Zampollo et al., 2018). Two Greek organisations are involved with the protection of sea turtles, ARCHELON and MEDASSET, both engaging volunteers and local communities to learn more about these protected species, their biology and conservation. ARCHELON tagged 12 individual females in June 2019, increasing the dataset of a long-term loggerhead tagging project, running since 1982 in conjunction with an annual nesting-activity monitoring program. You can even follow these 12 individual sea turtles here. MEDASSET are also trialling a program to detect marine litter using drones. This non-invasive pilot study will be vital in targeting areas of increased litter and possibly identifying entangled animals in distress, enabling a quick rescue. Ongoing campaigns like this span the Mediterranean including the turtle paradise, Cyprus. It seems sea turtles have won over the public and policymakers in Greece, with conservation initiative involvement increasing in popularity with tourists and locals, which is ‘turtlley’ awesome.

References

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Casale, P. (2010): Sea turtles in the Mediterranean: distribution, threats and conservation priorities. IUCN.

Casale, P., Broderick, A.C., Camiñas, J.A., Cardona, L., Carreras, C., Demetropoulos, A., Fuller, W.J., Godley, B.J., Hochscheid, S., Kaska, Y., Lazar, B., Margaritoulis, D., Panagopoulou, A., Rees, A.F., Tomás, J., and Türkozan, O. (2018): Mediterranean sea turtles: current knowledge and priorities for conservation and research. Endangered Species Research 36, 229-267.

Casale, P., and Heppell, S.S. (2016): How much sea turtle bycatch is too much? A stationary age distribution model for simulating population abundance and potential biological removal in the Mediterranean. Endangered Species Research 29, 239-254.

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Fuentes, M., Limpus, C., Hamann, M., and Dawson, J. (2010): Potential impacts of projected sea‐level rise on sea turtle rookeries. Aquatic conservation: marine and freshwater ecosystems 20, 132-139.

Hamilton, S., and Baker, G.B. (2019): Technical mitigation to reduce marine mammal bycatch and entanglement in commercial fishing gear: lessons learnt and future directions. Reviews in Fish Biology and Fisheries, 1-25.

Hatase, H., and Omuta, K. (2018): Nest site selection in loggerhead sea turtles that use different foraging areas: do less fecund oceanic foragers nest at safer sites? Journal of Zoology 305, 232-239.

Hu, Z., Hu, H., and Huang, Y. (2018): Association between night-time artificial light pollution and sea turtle nest density along Florida coast: A geospatial study using VIIRS remote sensing data. Environmental Pollution 239, 30-42.

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Marn, N., Jusup, M., Catteau, S., Kooijman, S.A.L.M., and Klanjšček, T. (2019): Comparative physiological energetics of Mediterranean and north Atlantic loggerhead turtles. Journal of Sea Research 143, 100-118.

Mazaris, A.D., Schofield, G., Gkazinou, C., Almpanidou, V., and Hays, G.C. (2017): Global sea turtle conservation successes. Science advances 3, e1600730.

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Aphrodite, the five-month old Mediterranean monk seal, born in Cyprus, was found dead on May 21st due to drowning in a fishing net. Source: In-Cyprus (2019).

On May 21^st and 22^nd 2019, Cyprus celebrated the 1992 ratification of Natura 2000 and World Biodiversity day with a special event (Happy #Natura200day).The European Union (EU) Natura network consists of 27,800 sites, covering 18% of EU land and 9.5% of its marine areas. With 63 Special Area of Conservation (SAC) sites in Cyprus alone, many of the most valuable and threatened species of local flora and fauna are protected.

One of the most critically-endangered species of seals in the world is the Mediterranean monk seal, Monachus monachus (Karamanlidis, 2015; Karamanlidis et al., 2016a). Endemic (i.e., only found in) to the Mediterranean , and predominantly in the Aegean Sea, half the population of ca. 600–700 individuals live in Greece, which is considered a stronghold for the species (MOm, 2007). Unfortunately in Cyprus, on the Natura 2000-day celebration, a five month old monk seal pup, Aphrodite, drowned in a fishing net, one of 14 recorded monk seals known to live in Cyprus waters. Out of respect for the seal, Cyprus’ Environmental Ministry (Fisheries department) launched an extensive clean up event of the Peyia sea caves, where seals are known to breed and rest, disposing of more than 2,200 kg of debris within the first day.

Current status

Monk seals belong to family of earless seals (Phocidae), consisting of the two genera Monachus and Neomonachus, the latter of which has been classified recently as a new genus, due mitochondrial DNA sequence analysis showing dissimilarities between both Caribbean (Neomonachus tropicalis) and Hawaiian monk seal, Neomonachus schauinslandi (Scheffer, 1958; Berta and Churchill, 2012). While the Caribbean monk seal became extinct in the 20^th Century due to hunting (Scheel et al., 2014; Lowry, 2015), the two remaining and extant monk seal species (Mediterranean and Hawaiian) are considered to be rare in numbers, facing imminent danger of extinction (Lowry et al., 2011; Scheel et al., 2014; Karamanlidis et al., 2016b).

A Mediterranean monk seal (Monachus monachus) swimming in the clear waters off the Greece coast. Source: Arkive.com

Ecology

Little is known about the Mediterranean monk seal and only recent research has begun to shed light on the ecology of this elusive species. Most information has been inferred from the ecology of their endangered relative, the Hawaiian monk seal, with 1,400 individuals remaining (Baker and Johanos, 2004). On average, Mediterranean monk seals can live up to 11-12 years and exhibit difference in size between males and females, known as sexual dimorphism (Karamanlidis, 2015). Larger males develop a mature pelage (fur coat) pattern over at least two annual moults, completed by the age of four, at which point they reach maturity, whilst females mature at 3-4 years of age (Badosa et al., 2006). Breeding is thought to occur throughout the year, peaking October–November (Gazo et al., 1999; Gucu et al., 2004), with females rearing pups on beaches or in caves, which always share similar geophysical properties, such as having an entrance above or below water level, an entrance corridor, and a dry surface/area (Dendrinos et al., 2007). This can be hazardous for new pups, with storm surges causing potential fatalities (Karamanlidis et al., 2016b). In Greece, more than 500 caves have been found to be occupied by the Mediterranean monk seal and more than 100 are used for pupping (MOm, 2007). Monk Seal activity in the marine caves in the eastern Mediterranean is highest in autumn and winter coinciding with their pupping season (Gucu et al., 2004). Although pupping is not strictly seasonal, individual females have been documented to give birth close to the same time in successive years, within a 15-day period (Pastor and Aguilar, 2003).

Illustration of life stages and sexual dimorphism of the Mediterranean monk seal. Source: Society Protection of Nature Lebanon (SPNL, 2016).

Monk seals in the eastern Mediterranean have been recorded travelling long distances, for example ca. 288 km in three months, with a maximal recorded distance of ca. 78 km (Adamantopoulou et al., 2011). Stomach-content analysis of dead monk seals has revealed a heterogeneous (mixed) diet consisting of bony fishes, cephalopods, and crustaceans. In Greece, Monk Seals are known to eat more than 70 prey species – 50% cephalopods, 48% fishes, 1.5% non-cephalopod molluscs, and 0.4% crustaceans (Pierce et al., 2011), most frequently common octopus (Octopus vulgaris, 34%), and bony fish from the family Sparidae (28%; Pierce et al., 2011). Contrary to many other pinnipeds, little is known about the species’ diving capabilities and behaviour.

Current threats

Habitat loss and deterioration, persecution by fishers, accidental mortality, entanglement in fishing gear, diseases, and pollution are all current threats to survival of the Mediterranean monk seal (MOm, 2007; Karamanlidis et al., 2016b). While low-pup survival rates are associated with mortality caused by severe storms, high swells and tides, decreased genetic diversity, and inbreeding may also be a source of the species’ decline (Pastor et al., 2007; Dendrinos, 2011; Karamanlidis et al., 2016a).

With a mass die off of pups in 1997 due to unknown causes (Gazo et al., 1999), the population is still in the process of recovery, with a current annual reproductive rate-average of 0.76 pups per female adult (Karamanlidis et al., 2016b). In Greece, annual pup survival appears to be increasing, most likely because lactating females and their pups have a higher number of suitable caves to choose from when seeking refuge from severe weather conditions (Dendrinos, 2011) and due to increased efforts of conservation organisations in Greece to designate special areas and restrict certain areas during breeding season (Karamanlidis, 2015).

The Mediterranean monk seal appears to be one of the most genetically depauperate (low variation) mammals on Earth (Karamanlidis et al., 2016a). With genetic diversity being a key driver in overall species health, genetically-heterogenous (different) individuals are more adaptable to survive new pathogens or environmental shifts (Pastor et al., 2007; Muraille, 2018). Mediterranean monk seals are thought to be subdivided into three or four metapopulations (i.e. separated groups), some of which are isolated geographically (Karamanlidis et al., 2016a) and only between 350–400 animals of breeding age persist (Karamanlidis et al., 2016b).

Monk seals are sensitive to human harassment (e.g. boating, diving, and tourism), and have been found seeking refuge in caves, as an adaptation to increased disturbance (Gucu et al., 2004). Historically, monk seals were driven from sandy shores during hunting events; however, more recently urban development, tourism, and habitat marginalisation are main causes for habitat loss (Karamanlidis et al., 2016b). Individuals are also known to depredate fishing nets, with juveniles being most at risk (Karamanlidis et al., 2008), while encounters, such as in the case of Aphrodite, are often fatal. Additionally, bycatch accounts for 24% of total mortality and occurs throughout the species’ range.

Conservation

Current action plans and systematic monitoring schemes are in place to help conserve the Mediterranean monk seal. The species is mentioned explicitly in 102 Natura 2000 sites within the EU (82 sites in Greece, 10 in Italy, 5 in Spain, 3 in Portugal, and 2 in Cyprus) and according to European Council Directive 92/43EEC ‘on The Conservation Of Natural Habitats Of Wild Fauna And Flora’ the Mediterranean Monk Seal is considered a species of community importance (Gucu et al., 2004; Dendrinos et al., 2007; Adamantopoulou et al., 2011; Karamanlidis et al., 2016a; Karamanlidis et al., 2016b). Natura 2000 sites are thus considered legally by EU member states as Protected Areas. These sites are enforced currently by the United Nations Environment Programme (UNEP) and Mediterranean Action Plans (first issued in 1978 and revised in 1988) for conservation, management and recovery of Monk Seals in the eastern Atlantic under the Migratory Species of Wild Animals Convention (CMS) or ‘the Bonn Convention’ (González, 2006). The ‘Regional Strategy for the Conservation of Monk Seals in the Mediterranean’ was devised with goals to be implemented between 2014-2019, enabling all countries within the monk seals’ range to adopt certain behaviours and legislations, to aid the species’ recovery (RAC/SPA, 2014). To date, results of this strategy are unknown; however, in 2015 the species was re-classified from ‘critically endangered’ to ‘endangered’ (Karamanlidis et al., 2016b).

Establishment of Marine Protected Areas (MPAs) to safeguard colonies and pupping areas for the Mediterranean monk seal have been shown to be an effective tool in conservation, as total numbers are increasing (Karamanlidis, 2015), while public opinion remains positive (Halkos et al., 2018). Fishing closures during breeding seasons have also been enforced to ensure safety of pups (Karamanlidis et al., 2008; Kıraç and Güçlüsoy, 2008). Additionally, use of Acoustic Deterrent Devices (ADDs) have also been discussed, utilised during fishing operations or in times of increased shipping traffic, to deter the animals from possible danger (Karamanlidis et al., 2008); however, there is no evidence of implementation of these devices to date. Seal count and distributional data are still being collected, and a new breeding site at Evia Island, Greece, has recently been discovered (Karamanlidis, 2015). In early 2018, two autonomous surveillance camera prototypes were installed at two different potential monk seal caves on the Greek Ionian islands and a fleet of aerial drones were used (through image-recognition technology) to locate and film elusive monk seals, with footage expected to be published by 2020 (IUCN, 2019). Researchers are also devising a genetic research protocol, with optimised sample collection and laboratory methods to be used in a preliminary assessment of genetic characteristics of monk seals in Greece (Karamanlidis et al., 2016a). A trailblazing marine protection initiative in Turkey has proven effective by leading community groups to patrol the no fish zones and MPAs, and there is increasing the hope that Greece may follow up soon (click here for details). Lack of novel and readily-available data on open source forums, as a result to the sensitive nature of this conservation issue, exacerbates the review of their current situation. After years of silence, it seems that the monk seal has won over the public’s and fishery’s opinion, and in conjunction with appropriate conservation and monitoring methods, hopefully, it will not share the same fate as the Caribbean monk seal. With ongoing research, the plight of the Mediterranean monk seal may not be in total vain, with new hope for their continued reign in the Mediterranean.

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OSC’s new paper ‘Meals on wheels? A decade of megafaunal visual and acoustic observations from offshore Oil & Gas rigs and platforms in the North and Irish Seas’ was published by PLoS One this month, and is available to download here.

The paper presents a decade of visual and acoustic detections of marine megafauna around offshore Oil & Gas (O&G) installations in the North and Irish Sea.  Marine megafauna activity was monitored visually and acoustically by Joint Nature Conservation Committee (JNCC) qualified and experienced Marine Mammal Observers (MMO) and Passive Acoustic Monitoring (PAM) Operators respectively, with real-time towed PAM in combination with industry standard software, PAMGuard. Monitoring was performed during routine O&G industrial operations for underwater noise mitigation purposes, and to ensure adherence to regulatory guidelines.

This study compliments OSC’s previous research on porpoises around O&G installations, and provides further evidence that marine megafauna are present around mobile and stationary offshore O&G installations during routine operational activities.

Minke whale (Balaenoptera acutorostrata) around the legs of an oil and gas installation

Since 2004, Ocean Science Consulting Ltd (www.osc.co.uk) have been providing offshore industries worldwide with top of the range marine mammal mitigation and noise monitoring services (www.osc.co.uk/services). In 2014, OSC expanded into New Zealand with the opening of their Asia-Pacific branch, OSC-NZ (www.osc-nz.co.nz), of which Erica (Morrin) Chapman (www.ericachapman.co.nz) and Jane (Gardiner) Warley (www.janewarley.co.nz) recently became shareholders, and Melanie Orr (www.melanieorr.co.nz) a Director.

Now, OSC would like to introduce OSC-GR. Benefiting from OSC’s peerless reputation and extensive experience, OSC-GR provides marine mammal mitigation services including provision of Marine Mammal Observers (MMO) and Passive Acoustic Monitoring (PAM) Operators and equipment.