IUCN Red List Assessment
Red List Category Year Assessed
Endangered Red List Criteria
Bearzi, G. Reviewer/s
Reeves, R.R. & Taylor, B. (Cetacean Red List Authority) Justification
At the outset, it is necessary to acknowledge that definitive quantitative data on absolute abundance and rate and extent of decline are not available for this subpopulation, and that it is unlikely that such data will become available in the near future. The Preamble of the 2001 IUCN Red List Categories, under Item 6, states that "the absence of high-quality data should not deter attempts at applying the criteria, as methods involving estimation, inference and projection are emphasized as being acceptable throughout ? so long as these can reasonably be supported." The abundant qualitative data and limited quantitative data that are available for the Mediterranean subpopulation of Common Dolphins are sufficient to infer a reduction in population size of more than 50% over a three-generation period (i.e., the past 30?45 years). [Note: Estimated age at sexual maturation varies with region, from three years (Black Sea) to 7?12 years (eastern Pacific) for males and from 2?4 years (Black Sea) to 6?7 years (eastern Pacific) for females (Perrin 2002). Variation between regions may be partly a result of density-dependent effects due to exploitation. Maximum estimated age is 22 years (Black Sea). These values support an estimate of generation time of 10?15 years.] The reduction or its causes may not have ceased, are not understood, and may not be reversible. These inferences are based on the expert judgment of researchers from the region who have observed declines in the number of animals (subcriterion a) and in the subpopulation?s extent of occurrence, as well as a deterioration in the quality of Common Dolphin habitat in large portions of the Mediterranean (subcriterion c). Although no formal index of abundance (subcriterion b) is available to demonstrate a numerical decline, there is reason to believe that such a decline has occurred, based on the species? progressive disappearance from the Adriatic, Balearic, and Ligurian Seas and Provençal Basin, the significant decline in group encounter rates in the eastern Ionian Sea (see documentation under Range and Population), and the reasonable assumption that a decline in abundance has been commensurate with the large (albeit unquantified) decline in extent of occurrence. For additional detail, readers are referred to Bearzi et al. (2003).
Consultation and peer review:
This assessment and the supporting documentation was drafted by Giovanni Bearzi in consultation with Ana Cañadas, Alexandros Frantzis, Giuseppe Notarbartolo di Sciara, Elena Politi, Randall Reeves, and Barbara Taylor. It was reviewed by the CSG membership prior to submission to IUCN.
No one has provided updates yet.