IUCN Red List Assessment
Red List Category
Red List Criteria
Smith, B.D. & Beasley, I.
Reeves, R. & Perrin, W.F. (Cetacean Red List Authority)
The best estimate of total subpopulation size is 77 individuals. Guidelines for considering measurement error (in Annex 1: Uncertainty, of the Red List Criteria) suggest using plausible lower bounds, rather than best estimates, to determine population size. In the case of Malampaya dolphins, this implies that it would be appropriate to use the lower 95% confidence interval, which is 45 individuals. Also, the threshold of 50 mature individuals for listing a species or population as CR according to Criteria D (and C2a(i)) refers to the number of individuals known, estimated or inferred to be capable of reproduction. Although the proportion of mature individuals typical for this species is unknown, it is reasonable (and certainly precautionary) to infer that the number of mature individuals in Malampaya Sound is less than 50. Therefore, the population qualifies for listing as CR based on Criterion D. The population also qualifies as CR on the basis of Criterion C2a (i, ii) as there are certainly fewer than 250 mature individuals in the population, a continuing decline in the number of mature individuals is projected or inferred based on the ongoing threat from gillnet entanglement, and both subcriteria of subcriterion 2a apply (no subpopulation contains more than 50 mature individuals, and more than 90% of the total mature individuals are in one subpopulation).
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