Biodiversity and Ecosystem (EO 1)

Common indicator 5: Population demographic characteristics - Marine Mammals

Geographical scale of the assessment:
Regional, Mediterranean Sea
Contributing countries:
Mid-Term Strategy (MTS) Core Theme:
2-Biodiversity and Ecosystems
Ecological Objective:
EO1: Biological diversity is maintained or enhanced. The quality and occurrence of coastal and marine habitats and the distribution and abundance of coastal and marine species are in line with prevailing physiographic, hydrographic, geographic and climatic conditions.
IMAP Common Indicator:
Common Indicator 5 (CI5): Population demographic characteristics (e.g. body size or age class structure, sex ratio, fecundity rates, survival/mortality rates related to marine mammals)
Indicator Assessment Factsheet Code:

GES Definition

  • Cetaceans: Species populations are in good condition: Low human induced mortality, balanced sex ratio and no decline in calf production.
  • Monk Seal: Species populations are in good condition: Low human induced mortality, appropriate pupping seasonality, high annual pup production, balanced reproductive rate and sex ratio.

GES Targets:

  • State: Decreasing trends in human induced mortality.
  • Pressure (cetaceans): Appropriate measure implemented to mitigate incidental catch, prey depletion and other human induced mortality.
  • Pressure (monk seals): Appropriate measures implemented to mitigate direct killing and incidental catches and to preclude habitat destruction.



The objective of this indicator is to focus on the population demographic characteristics of marine mammals within the Mediterranean waters. Demographic characteristics of a given population may be used to assess its conservation status by analysing demographic parameters as the age structure, age at sexual maturity, sex ratio and rates of birth (fecundity) and of death (mortality). These data are particularly difficult to obtain for marine mammals, thus relying on demographic models, all of which make assumptions that may be violated in practice.

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Assessment methods                           

Monitoring effort should be directed to collect long-term data series covering the various life stages of the selected species. This would involve the participation of several teams using standard methodologies and covering sites of particular importance for the key life stages of the target species.

The preliminary classical tools for demographic analyses are life tables, accounting for the birth rates and probabilities of death for each vital stage or age class in the population.

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Fin whale - Demographic models - commonly used in animal and plant populations - have been applied to marine mammals and cetaceans only in the recent years. Usually, two different approaches are used when dealing with demographic studies, based on static or cohort life-tables. A third approach refers to the use of mortality tables and provides detailed information about size⁄age and sex of dead individuals.

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Available data on demography for Mediterranean marine mammals are rather scarce and fragmented and at present it is rather difficult to provide strong and robust evidence on baselines and changes over time in demographic parameters.

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Key messages 

  • Systematic and long-term photo-identification programs, jointly to the use of appropriate instruments to measure observed animals, would be essential tools to supply basic knowledge on population structure needed for conservation plans.

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Arrigoni, M., Manfredi, P., Panigada, S., Bramanti, L., Santangelo, G. 2011. Life-tables of the Mediterranean fin whale set out from stranding data. Marine Ecology: an evolutionary perspective, 32(1):1-9.doi:10.1111/j.1439-0485.2011.00437.x

Butti, C., Corain, L., Cozzi, B., Podestà, M., Pirone, A., Affronte, M., Zotti, A., 2007. Age estimation in the Mediterranean bottlenose dolphin Tursiops truncatus (Montagu 1821) by bone density of the thoracic limb. J. Anat. 211, 639–646. doi:10.1111/j.1469-7580.2007.00805.x

Đuras, M., Divac Brnić, D., Gomerčić, T., Galov, A., 2014. Craniometry of bottlenose dolphins (Tursiops truncatus) from the Adriatic Sea. Veterinary Archives 84, 649–666.

Gol’din, P., Gladilina, E., 2015. Small dolphins in a small sea: age, growth and life history aspects of the Black Sea common bottlenose dolphin Tursiops truncatus. Aquatic Biology 23, 159–166. doi:10.3354/ab00617

Karamanlidis, A. A., and P. Dendrinos. 2015. Monachus monachus. The IUCN Red List of Threatened Species.

Kerem, D., Kent, R., Roditi-Elasar, M., Goffman, O., Scheinin, A., Gol’din, P., 2013. Early physical maturation of female common bottlenose dolphin in the eastern Levantine Basin. Israel Journal of Ecology & Evolution 59, 154–162. doi:10.1080/15659801.2013.892297

Pribanić, S., Mioković, D., Kovačić, D., 2000. Preliminary growth rate and body lengths of the bottlenose dolphins Tursiops truncatus (Montagu, 1821) from the Adriatic Sea. Natura Croatica 9, 179–188.

Rossi, A., Panigada, S., Arrigoni, M., Zanardelli, M., Cimmino, C., Marangi, L., Manfredi, P., Santangelo, G., 2014. Demography and conservation of the Mediterranean fin whale (Balaenoptera physalus): what clues can be obtained from photo-identification data. Theor Biol Forum 107, 123–142.

Rossi, A., Scordamaglia, E., Bellingeri, M., Gnone, G., Nuti, S., Salvioli, F., Manfredi, P., Santangelo, G., 2017. Demography of the bottlenose dolphin Tursiops truncatus (Mammalia: Delphinidae) in the Eastern Ligurian Sea (NW Mediterranean): quantification of female reproductive parameters. The European Zoological Journal 84, 294–302. doi:10.1080/24750263.2017.1334839

Sharir, Y., Kerem, D., Gol’din, P., Spanier, E., 2011. Small size in the common bottlenose dolphin ­Tursiops truncatus in the eastern Mediterranean: a possible case of Levantine nanism. Marine Ecology Progress Series 438, 241–251. doi:10.3354/meps09282

UNEP-MAP-RAC/SPA, IUCN. 1988. Report of the joint expert consultation on the conservation of the Mediterranean monk seal. Athens, 11-12 January 1988. IUCN/UNEP/MEDU/MM-IC/5. 8 p

UNEP-MAP-RAC/SPA. 2003. Action Plan for the management of the Mediterranean monk seal (Monachus monachus). Reprinted, RAC/SPA, Tunis. 12 p.