Hellenic Trench IMMA

Area Size

56 568 km2

Qualifying Species and Criteria

Sperm whale – Physeter macrocephalus

Criterion A; B (i, ii); C (i, ii); D (i)

Cuvier’s beaked whale – Ziphius cavirostris 

Criterion A; B (ii); C (i, ii); D (i)

Marine Mammal Diversity 

Criterion D (ii)

Stenella coeruleoalba, Grampus griseus, Delphinus delphis, Tursiops truncatus, Monachus monachus


The Hellenic Trench is a long bathymetric feature in the eastern Mediterranean consisting of a continuous steep continental seaward slope, often bounding offshore linear trenches, troughs and basins, which reach 5 km in depth. The area is the core habitat for the eastern basin distribution of the Endangered Mediterranean sperm whale (Physeter macrocephalus) subpopulation. This eastern Mediterranean distribution includes some 200-250 animals threatened by potentially unsustainable ship-strikes. Additionally, the Hellenic Trench features a sub-area which is the largest among five high-density areas of Mediterranean occurrence for Vulnerable Cuvier’s beaked whales (Ziphius cavirostris) that have suffered repeated mass stranding events in the area.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

The IUCN Red List classifies the Mediterranean subpopulation of sperm whale as Endangered and infers that their numbers are declining from significant anthropogenic threats. These whales are likely to be genetically isolated from the Atlantic population. Furthermore the subpopulation of Cuvier’s beaked whale in the Mediterranean Sea is listed as Vulnerable (VU) C2a(ii) IUCN Red List of Threatened Species, with a decreasing population trend (Cañadas and Notarbartolo di Sciara, 2018).

Criterion B: Distribution and Abundance

Sub-criterion Bi: Small and Resident Populations

The area is a core habitat for sperm whales in the eastern Mediterranean, with most of the Eastern Mediterranean subpopulation being resident in or visiting the area. Although the eastern Mediterranean basin subpopulation is smaller than that in the western basin, the entire Mediterranean population is small, such that numbers of sperm whales using the area are a substantial portion of the whole Mediterranean population. While there are many photographic recaptures of individuals within the individual western and eastern Mediterranean basins there are only three cases of animals moving from the western basin to the eastern basin, suggesting that though not isolated the western and eastern subpopulations are predominantly separate.

Sub-criterion Bii: Aggregations

Within the Hellenic Trench whales were observed to have a very pronounced peak in density over the 1,000m isobath on the slopes of the landward side of the trench. This combination of slope, aspect and depth appears to represent a significant zone for aggregating sperm whales in the eastern Mediterranean making the Hellenic Trench the core habitat for the subpopulation of the entire eastern basin. Such consistent and predictable aggregations can enable effective management actions to reduce the risk of ship strikes (such as through minor routing changes) which are recognised by the IMO as an effective way to address the ship strike issue.

Criterion C: Key Life Cycle Activities

Sub-criterion Ci: Reproductive Areas

The area appears to be the core habitat for sperm whale in the eastern Mediterranean for calving and nursing. Calves (≤2 years old) were present in 79% of social unit encounters, accounting for 17% of social unit members within the area. Observations of 15 newborns indicate a mid-summer calving season which would imply a mating season from late winter to late spring. Though no observations of mating within the area have been reported, this mating season lies outside the normal fieldwork season, which may explain the lack of such observations so far.

Calves have been observed during sightings of Cuvier’s beaked whales and also have repeatedly stranded along the Hellenic Trench, including newborns bearing foetal folds, the most recent being on the Island of Rhodes in September 2016. During the last mass stranding of Cuvier’s beaked whales in southern Crete in April 2014, a fully formed foetus was found in a necropsied stranded female animal. These data show that the area constitutes a reproductive area for the species.

Sub-criterion Cii: Feeding Areas

The area is an important feeding ground for the eastern Mediterranean sperm whale subpopulation. Solitary males, loose male aggregations and members of long-term resident social units of sperm whales were observed feeding in the area, with foraging and feeding activities being confirmed acoustically.

Cuvier’s beaked whales utilizing a portion of the area is important for their feeding activities. Cuvier’s beaked whales have similar same feeding habits as sperm whales and both species inhabit the area because of the presence of their prey. Long lasting deep feeding dives have been repeatedly observed along the Hellenic Trench and stomach contents of stranded animals contained primary meso- and bathy-pelagic species that are also found in sperm whale stomachs of stranded sperm whales in the very same area.

Criterion D: Special Attributes  

Sub-criterion Di: Distinctiveness

The Mediterranean population of sperm whales are genetically and culturally different from their conspecifics in the Atlantic Ocean. In addition, at the local level of the eastern Mediterranean, social units are likely to be resident and may not migrate out of this basin. Distinctive communication sounds (codas) produced by males and social units in the Hellenic Trench have not been recorded in the western Mediterranean so to date. This is an indication that cultural evolutionary processes may have affected coda dialects differently in the eastern Mediterranean basin compared to the western Mediterranean, as the repertoires of codas are acquired by cultural transmission, a process that occurs at the level of core social units. The Mediterranean population of Cuvier’s beaked whales are also genetically different from conspecifics in the Atlantic Ocean.

Sub-criterion Dii: Diversity

The area includes the regular presence of seven marine mammal species including Sperm whale, Cuvier’s beaked whale, Striped dolphin, Risso’s dolphin, Common dolphin, Common bottlenose dolphin, and Monk seal. It is possible that Rough toothed dolphins also use the area as they have been sighted in neighbouring areas with similar habitats. Therefore, the Hellenic Trench area is considered to have an important diversity Mediterranean marine mammals.

Supporting Information

ACCOBAMS, 2013. Report of the Fifth Meeting of the parties to ACCOBAMS, Tangier 5-8 November 2013. Recommendation 8.6: Recommendation on the conservation of Cuvier’s beaked whales in the Mediterranean. “Areas of Special Concern for Beaked Whales” (ASC-BW) and mitigation protocols for anthropogenic activities using intense underwater sound sources. Appendix 1: Mediterranean beaked whale mortality events associated with naval manoeuvres and/or use of military sonar.

Agardy, T., Aguilar, N., Cañadas, A., Engel, M., Frantzis, A., Hatch, L., Hoyt, E., Kaschner, K., LaBrecque, E., Martin, V., Notarbartolo di Sciara, G., Pavan, G., Servidio, A., Smith, B., Wang, J., Weilgart, L., Wintle, B. and Wright, A. 2007. A Global Scientific Workshop on Spatio-Temporal Management of Noise. Report of the Scientific Workshop. 44pp.

Boisseau, O., Lacey, C., Lewis, T., Moscrop, A., Danbolt, M., McLanaghan, R., 2010. Encounter rates of cetaceans in the Mediterranean Sea and contiguous Atlantic area. J. Mar. Biol. Assoc. United Kingdom 90, 1589–1599.

Cañadas, A., 2012. Ziphius cavirostris (Mediterranean subpopulation). The IUCN Red List of Threatened Species 2012: e.T16381144A16382769. http://dx.doi.org/10.2305/IUCN.UK.2012-1.RLTS.T16381144A16382769.en

Cañadas, A. et al. 2016. ACCOBAMS collaborative effort to map high-use areas by beaked whales in the Mediterranean. ACCOBAMS Report (available from ACCOBAMS)

Carpinelli, E., Gauffier, P., Verborgh, P., Airoldi, S., David, L., Di-Méglio, N., Cañadas, A., Frantzis, A., Rendell, L., Lewis, T., Mussi, B., Pace, D. S. and De Stephanis, R. 2014. Assessing sperm whale (Physeter macrocephalus) movements within the western Mediterranean Sea through photo-identification. Aquatic Conserv: Mar. Freshw. Ecosyst., 24: 23–30. doi: 10.1002/aqc.2446

Cañadas, A. and Notarbartolo di Sciara, G. 2018. Ziphius cavirostris Mediterranean subpopulation. The IUCN Red List of Threatened Species 2018: e.T16381144A50286386. http://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T16381144A50286386.en. Downloaded on 29 January 2019.

Dalebout, M.L., Robertson, K.M., Frantzis, A., Engelhaupt, D., Mignucci-Giannoni, A.A., Rosario-Delestre, R.J., Baker, S.C. 2005. Worldwide structure of mtDNA diversity among Cuvier’s beaked whales (Ziphius cavirostris): implications for threatened populations Molecular Ecology, 14: 3353-3371.

Engelhaupt, D., Hoelzel, A.R., Nicholson, C., Frantzis, A., Mesnick, S., Gero, S., Whitehead, H., Rendell, L., Miller, P., De Stefanis, R., Cañadas, A., Airoldi, S. and Mignucci-Giannoni, A.A. 2009. Female philopatry in coastal basins and male dispersion across the North Atlantic in a highly mobile marine species, the sperm whale (Physeter macrocephalus). Mol Ecol. 18: 4193–4205.

Frantzis, A. 1998. Does acoustic testing strand whales? Nature, 392: 29.

Frantzis, A., Alexiadou, P., Paximadis, G., Politi, E., Gannier, A., Corsina-Foka, M. 2003. Current knowledge of the cetacean fauna of the Greek Seas. J. Cetacean Res. Manag. 5, 219–232.

Frantzis, A. 2004. The first mass stranding that was associated with the use of active sonar (Kyparissiakos Gulf, Greece, 1996). In: Proceedings of the workshop: “Active sonar and cetaceans “. 8 March 2003, Las Palmas, Gran Canaria. ECS newsletter 42 (special isssue): pp. 14-20.

Frantzis, A., Alexiadou, P. 2008. Male sperm whale (Physeter macrocephalus) coda production and coda-type usage depend on the presence of conspecifics and the behavioural context. Can. J. Zool. 86, 62–75. doi:10.1139/Z07-114

Frantzis, A. 2009. Cetaceans in Greece: Present status of knowledge. Initiative for the Conservation of Cetaceans in Greece, Athens, Greece, 94 pp.

Frantzis A, Airoldi S, Notarbartolo di Sciara G, Johnson C, Mazzariol S. 2011. Inter-basin movements of Mediterranean sperm whales provide insight into their population structure and conservation. Deep Sea Research I 58: 454–459.

Frantzis, A., Alexiadou, P., Gkikopoulou, K.C. 2014a. Sperm whale occurrence, site fidelity and population structure along the Hellenic Trench (Greece, Mediterranean Sea). Aquat. Conserv. Mar. Freshw. Ecosyst. 24, 83–102.

Frantzis, A., Leaper, R., Alexiadou P., & Lekkas, D. 2014b. Distribution patterns of sperm whales in relation to shipping density in the Hellenic Trench, Greece. Paper presented to IWC Scientific Committee, Bled, Slovenia, 12-24 May 2014, SC/65b/HIM07

Frantzis, A., Leaper, R., Paraskevi, A., Lekkas, D. 2015. Update on sperm whale ship strike risk in the Hellenic Trench, Greece. Paper presented to IWC Scientific Committee, San Diego, CA, USA, 22 May-3 June 2015, SC/66a/HIM06.

Frantzis, A. 2015. Short report on the mass stranding of Cuvier’s beaked whales that occurred on the 1st of April 2014 in South Crete, Greece, during naval exercises. FINS 6.1, 10-11. (The Newsletter of ACCOBAMS).

IMO. 2016. Draft report of the Marine Environment Protection Committee on its Sixty-Ninth Session. MEPC 69/WP.1.

Laran, S., Pettex, E., Authier, M., Blanck, A., David, L., Doremus, G., Falchetto, H., Monestiez, P., Van Canneyt, O. and Ridoux, V. 2015. Seasonal distribution and abundance of cetaceans within French waters- Part I: the northwestern Mediterranean, including the Pelagos sanctuary. Manuscript accepted for publication in Deep-Sea Res Part II.

Legakis, A., Maragkou, P. 2009. The Red Book of Threatened Animal Species of Greece. Hellenic Zoological Society. 528 p. (in Greek)

Lefkaditou, E., Poulopoulos, Y. 1998. Cephalopod  remains  in the  stomach-content  of beaked whales, Ziphius  cavirostris (Cuvier,  1823), from the  Ionian  Sea. Rapp. Comm. Int. Mer. Médit. 35, p. 460.

Lewis, T., Gillespie, D., Lacey, C., Matthews, J., Danbolt, M., Leaper, R., McLanaghan, R., Moscrop, A. 2007. Sperm whale abundance estimates from acoustic surveys of the Ionian Sea and Straits of Sicily in 2003. J. Mar. Biol. Assoc. United Kingdom 87, 353–357.

Lewis, T., Boisseau, O., Danbolt, M., Gillespie, D., Lacey, C., Leaper, R., Matthews, J, McLanaghan, R., Moscrop, A. 2017. Abundance estimates for sperm whales in the Mediterranean Sea from acoustic line-transect surveys. Journal of Cetacean Research and Management. Open Research Exeter, https://ore.exeter.ac.uk/repository/handle/10871/27538

Notarbartolo di Sciara, G., Frantzis, A., Bearzi, G., Reeves, R. 2012. Physeter macrocephalus (Mediterranean subpopulation), in: IUCN Red List of Threatened Species. Version 2013.1. Downloaded on 04 February 2013 from www.iucnredlist.org., In: IUCN 2010. IUCN Red List of Threatened Species. Version 2010.4. Downloaded from www.iucnredlist.org.

Öztürk, A. A., Tonay, A., Dede, A. 2013. Sperm whale (Physeter macrocephalus) sightings in the Aegean and Mediterranean part of Turkish waters. J. Black Sea/Mediterranean Environment Vol. 19, No. 2: 169˗177.

Peltier, H., Dabin, W., Daniel, P., Van Canneyt, O., Dorémus, G., Huon, M., Ridoux, V. 2012. The significance of stranding data as indicators of cetacean populations at sea: Modelling the drift of cetacean carcasses. Ecological Indicators 18: 278–290.

Pirotta, E., Matthiopoulos, J., MacKenzie, M., Scott-Hayward, L., Rendell, L. 2011. Modelling sperm whale habitat preference: a novel approach combining transect and follow data. Mar. Ecol. Prog. Ser. 436, 257–272.

Podestà, M., Azzellino, A., Cañadas, A., Frantzis, A., Moulins, A., Rosso, M., Tepsich, P., Lanfredi, C. 2016. Cuvier’s beaked whale (Ziphius cavirostris) presence and threats in the Mediterranean Sea, in: Notarbartolo di Sciara, G., Podestà, M., Curry, B.E. (Eds.), Mediterranean Marine Mammals Ecology and Conservation. Adv. Mar. Biol. 75, Elsevier, pp. 103–140.

Rendell, L., Mesnick, S.L., Dalebout, M.L., Burtenshaw, J., Whitehead, H. 2012. Can genetic differences explain vocal dialect variation in sperm whales, Physeter macrocephalus ? Behav. Genet. 42, 332–43. doi:10.1007/s10519-011-9513-y

Rendell, L., Simião, S., Brotons, J.M., Airoldi, S., Fasano, D., Gannier, A. 2014. Abundance and movements of sperm whales in the western Mediterranean basin. Aquat. Conserv. Mar. Freshw. Ecosyst. 24, 31–40.

Rendell, L., Frantzis, A. 2016. Mediterranean sperm whales, Physeter macrocephalus: The precarious state of a lost tribe, in: Notarbartolo di Sciara, G., Podestà, M., Curry, B.E. (Eds.), Mediterranean Marine Mammals Ecology and Conservation. Adv. Mar. Biol. 75, Elsevier, pp. 37–74.


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