Alborán Sea IMMA

Area Size

55 938 km2

Qualifying Species and Criteria

Common dolphin – Delphinus delphis

Criterion A; B (2); C (1, 2); D (1)

Common bottlenose dolphin – Tursiops truncatus

Criterion A; B (2); C (1, 2); D (1)

Marine Mammal Diversity 

Criterion D (2)

Balaenoptera physalus, Globicephala melas, Orcinus orca, Grampus griseus, Physeter macrocephalus, Ziphius cavirostris, Stenella coeruleoalba

Summary

The Alborán Sea, the westernmost part of the Mediterranean Sea, opens to the Atlantic Ocean through the Strait of Gibraltar, becoming a transition area between these two basins which have radically different oceanographic characteristics. This transition area contains important habitat for Endangered Mediterranean common dolphins (Delphinus delphis) and Vulnerable common bottlenose dolphins (Tursiops truncatus). In addition, the area contains an important diversity of cetacean species, the highest such diversity observed within the Mediterranean Sea.

Description of Qualifying Criteria

Criterion A – Species or Population Vulnerability

The common dolphin Mediterranean subpopulation is listed as Endangered in the IUCN Red List of Threatened Species. This area has the largest concentration of the common dolphin subpopulation within the whole Mediterranean, containing the large majority of the total population, both due to large density of groups and due to very large group sizes, much larger than anywhere else in the Mediterranean. The most recent abundance estimate of common dolphin is of 19,082 (CV=4.7%) animals only in the northern third of the Alborán Sea with an extension to include the Alborán island.

The common bottlenose dolphin Mediterranean subpopulation is listed as Vulnerable in the IUCN Red List of Threatened Species. The Alborán Sea also has large concentrations of bottlenose dolphins, which also present some of the largest group sizes in the Mediterranean. The latest estimate of abundance of bottlenose dolphin in the northern third of the Alborán Sea with an extension to include the Alborán island is 2,150 animals (CV=24.3).

Criterion B: Distribution and Abundance

Sub-criterion B2: Aggregations

Large numbers of both common and bottlenose dolphins inhabit the Alboran Sea area, both in terms of number of groups encountered and on the mean size of the groups. Data has been gathered in this area from 1992 to 2011 (20 years), for all seasons but mainly during the summer months. The largest concentrations of the common dolphin are observed for this subpopulation within the whole Mediterranean, containing the large majority of the total population, both due to large density of groups and due to very large group sizes, much larger than anywhere else in the Mediterranean. The most recent abundance estimate is of 19,082 (CV=4.7%) animals only in the northern third of the Alborán Sea with an extension to include the Alborán Island and 1966 animals (CV=0.11%) in the Strait of Gibraltar.

This area has also large concentrations of bottlenose dolphins, which also present the larger group sizes in the Mediterranean (Cañadas and Hammond 2006). The latest estimate of abundance of bottlenose dolphin in the northern third of the Alboran Sea with an extension to include the Alborán island is 2,150 animals (CV=24.3), for the Strait of Gibraltar 297 (CV=6.0%) animals, and for the southern area along the coasts of Morocco and Algeria 870 (CV=11%) animals.

Criterion C: Key Life Cycle Activities

Sub-criterion C1: Reproductive Areas

Both common dolphin and bottlenose dolphin species are seen mating and with calves in every year, including records of newborns. Data has been gathered in this area from 1992 to 2011 (20 years), for all seasons but mainly in summer. Calves for both species have been observed all years. Groups with calves have been modelled through density surface modelling (as opposed to groups with no calves) for common dolphins showing a more coastal usage of the area when calves are in the groups. Within the Strait of Gibraltar, the Bay of Algeciras has been identified as an area especially important for caring of young common dolphins.

Sub-criterion C2: Feeding Areas

Both species are very frequently observed feeding in the Alborán Sea and Strait of Gibraltar. Data has been gathered in this area from 1992 to 2015 (23 years), in all seasons but mainly in summer. Foraging and feeding have been observed year-round, across all years of study, for both common dolphins and bottlenose dolphins. The distribution of Groups feeding have been modelled through density surface modelling (as opposed to groups not feeding) for common dolphins showing a more coastal usage of the area when feeding. In the Strait of Gibraltar, the Bay of Algeciras has been identified as an important feeding ground for common dolphins, especially at the end of the summer, where dolphins were observed preying on flying fishes, anchovies, sardines. Bottlenose dolphins have been observe actively foraging/feeding in 20% of the encounters, and up to 30% in the shallower waters of the continental shelf (up to 200m depth).

Criterion D: Special Attributes  

Sub-criterion D1: Distinctiveness

Genetic research has shown that the common dolphins within the Alborán Sea are genetically different than those in the rest of the Mediterranean. Bottlenose dolphins in the Western Mediterranean are differentiated genetically from those in the Eastern Mediterranean and North East Atlantic. Both nuclear and mtDNA analyses showed clear differentiation between the Ionian and Alboran populations. Considering the relative proximity of these populations, such marked differentiation was unexpected. The common dolphin is a highly mobile species capable of long distance dispersion, confirmed by the lack of strong population structure observed among North and South Atlantic populations. It is further considered that common dolphins within the Alborán Sea may also be distinctive within the Mediterranean region. In a genetic analysis of bottlenose dolphins in the Black Sea, Mediterranean Sea and North East Atlantic show a strong boundary between the western and eastern basins of the Mediterranean Sea, separated by the Italian peninsula. Furthermore, of the five samples collected nearest to the Strait of Gibraltar and Almeria-Oran frontal region, four were near a boundary region in the multi-dimensional scaling plot, supporting the possibility that this oceanic front represents a relevant boundary to gene flow.

Sub-criterion D2: Diversity

The Alborán Sea is an area of high cetacean species diversity including killer whales, sperm whales, long-finned pilot whales, Cuvier’s beaked whales and Risso’s dolphins, striped, common and bottlenose dolphins. Furthermore there are regular, though with less density, presence of migrating fin whales. Additional North Atlantic vagrants make it the area of highest cetacean diversity in the Mediterranean.

Supporting Information

Cañadas, A., Cosentino, A., Arso, M., Esteban, R., de Stephanis, R., Verborgh, P. 2013. Survival rate and estimation of immigration in the Alboran Sea bottlenose dolphin population. 20th Biennal Conference on Marine Mammals, Dunedin, New Zealand, 9-13 December 2013. Descarga el poster en pdf.

Arnone, R.A. and La Violette, P.E. 1984. Satellite Definition of the Bio-Optical and Thermal Variation of Coastal Eddies Associated with the African Current. NORDA Technical Note 291.

Bearzi, G., Reeves, R.R., Notarbartolo di Sciara, G., Politi, E., Cañadas, A., Frantzis, A., Mussi, B. 2003. Ecology, status and conservation of short-beaked common dolphins Delphinus delphis in the Mediterranean Sea. Mammal Rev. 33, 224–252.

Cañadas, A. & Hammond, P.S. 2006. Model-based abundance estimates for bottlenose dolphins off southern Spain: implicationsfor conservation and management. Journal of Cetacean Research and Management 18(1): 13-27.

Cañadas, A. and Sagarminaga, R. 2000. The northeastern Alboran Sea, an important breeding and feeding ground for the long-finned pilot whale (Globicephala melas) in the Mediterranean Sea. Marine Mammal Science 16(3): 513-529.

Cañadas, A. and Sagarminaga, R. 2002. Identificación de las áreas de especial interés para la conservación de los cetáceos en el Mediterráneo español. Report available from (Cañadas, A.).

Cañadas, A., and Vazquez, J.A. 2017. Common dolphins in the Alboran Sea: facing a reduction in their suitable habitat due to an increase in sea surface temperature. Deep Sea research II. 141: 36-318.

Cañadas, A., Hammond, P.S. 2008. Abundance and habitat preferences of the short-beaked common dolphin Delphinus delphis in the southwestern Mediterranean: Implications for conservation. Endangered Species Research,4,3,309,331

Cañadas, A., Sagarminaga, R., de Stephanis, R., Urquiola, E., Hammond, P.S. 2005. Habitat preference modelling as a conservation tool: proposal of marine protected areas for cetaceans in Southern Spain. Aquat. Conserv. 15, 495-521.

Cañadas, A., Sagarminaga, R., García-Tiscar, S. 2002. Cetacean distribution related with depth and slope in the Mediterranean waters off southern Spain. Deep Sea Res. I, 49(11), 2053-2073.

Cañadas, A., Vázquez, J.A. 2014. Conserving Cuvier’s beaked whales in the Alborán Sea (SW Mediterranean): Identification of high density areas to be avoided by intense man-made sound. Biol. Conserv. 178, 155-162.

Carpinelli, E., Gauffier P., Verborgh, P., et al. 2011. Assessing sperm whale (Physeter macrocephalus) movements within the Mediterranean Sea through photo-identification. Aquatic Conserv: Mar. Freshw. Ecosyst., 24: 23–30. doi: 10.1002/aqc.2446

Chico Portillo, et al. 2011. Survival rate, abundance and residency of bottlenose dolphins (Tursiops truncatus) in the Strait of Gibraltar. 25th Ann. Meeting European Cetacean Society, Cadiz, Spain, March 2011

De Stephanis, R. et al. 2008. Summer spatial distribution of cetaceans in the Strait of Gibraltar in relation to the oceanographic context. Marine Ecology Progress Series,353, 275-288

Esteban, R. et al. 2013. Identifying key habitat and seasonal patterns of a critically endangered population of killer whales. Journal of the Marine Biological Association of the United Kingdom. doi:10.1017/S002531541300091X

Esteban et al. 2016c. Using a multi-disciplinary approach to identify a critically endangered killer whale management unit. Ecological Indicators 66, 291-300

Esteban R. et al. 2016d. Conservation Status of Killer Whales, Orcinus Orca, in the Strait of Gibraltar. Advances in Marine Biology.75

Gauffier et al. 2015. Desde Ceuta hasta Saidia, abundancia y movimientos de delfines mulares en el Sur del mar de Alborán. Oral presentation at the Sociedad Española de Cetáceos. Vigo.

Giménez, J., et al. 2011. The Bay of Algeciras: a feeding and a breeding ground for common dolphins? 25th Ann. Meeting European Cetacean Society, Cadiz, Spain, March 2011.

Giménez et al. 2012. Abundance of common dolphins in the Bay of Algeciras using mark-recapture data. 26th Ann. Meeting European Cetacean Society, Galway, Ireland, 26-28 March 2012.

INDEMARES Report. 2010. Available from Fundacion Biodiversidad, Spain.

Kaschner, K., et al. 2016. AquaMaps: Predicted range maps for aquatic species. World wide web electronic publication, www.aquamaps.org, Version 08/2016.

Laplanche, C., Adam, O. & Motsh, J. 2004. Accuracy in the localization of Sperm whales resident in the Strait of Gibraltar using one hydrophone. Can. Acoust. 32, 161–166.

La Violette, P.E. 1986. Short-term Measurements of Surface Currents Associated with the Alborán Sea Gyre during Donde Va?. Journal of Physical Oceanography, 16: 262-279.

Natoli, A., Birkun, A., Aguilar, A., Lopez, A., Hoelzel, A.R. 2005. Habitat structure and the dispersal of male and female bottlenose dolphins (Tursiops truncatus) Proc. R. Soc. B., 272, 1217-1226.

Natoli, A., Cañadas, A., Peddermors, V.M., Aguilar, A., Vaquero, C., Fernández-Piqueras, P., Hoelzel, A.R. 2006. Phylogeography and alpha taxonomy of the common dolphin (Delphinus sp.), J. Evol. Biol., 19, 943-954.

Natoli, A., Cañadas, A., Vaquero, C., Politi, E., Fernandez-Navarro, P., Hoelzel, A.R. 2008. Conservation genetics of the short-beaked common dolphin (Delphinus delphis) in the Mediterranean Sea and in the eastern North Atlantic Ocean, 2008, Conservation Genetics,9,6:1479-1487

Rodriguez, J., 1982. Oceanografía del Mar Mediterráneo. Ed. Pirámide. 174 p.
Rubín JP. 1994. El ictioplacton y el medio marino en los sectores norte y sur del mar de Alborán, en junio de 1992. Informe Técnico del Instituto Español de Oceanografía 146.

Rubín, J.P., Gil, J., Ruiz, J., Cortés, M.D., Jiménez-Gómez, F., Parada, M. and Rodriguez, J. 1992. La distribución ictioplanctónica y su relación con parámetros físicos, químicos y biológicos en el sector norte del Mar de Alboran, en julio de, 1991 (Resultados de la Campaña “Ictio.Alboran 0791”). Informe Técnico del Instituto Español de Oceanografía, 139. Madrid.

Tintoré, J., La Violette, P.E., Blade, I. y Cruzado, A. 1988. A Study of an Intense Density Front in the Eastern Alboran Sea: The Almería-Oran Front. Journal of Physical Oceanography, 18(10) American Meteorological Society.

Verborgh et al. 2009. Survival rate, abundance, and residency of long-finned pilot whales in the Strait of Gibraltar. MMS

Verborgh et al. 2016. Conservation Status of Long-Finned Pilot Whales, Globicephala melas, in the Mediterranean Sea. Advances in Marine Biology. 75

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