CR

Critically Endangered

C2a(ii);D

3.1

The Baiji is probably the most threatened cetacean in the world. It is a relict species and the only living representative of the family Lipotidae (Zhou, Qian and Li 1978). It meets the definition of a Critically Endangered (CR) species, as it is facing an extremely high risk of extinction in the wild.

Criterion A. Although the species may qualify as CR under this criterion, the lack of standardized survey data makes it difficult to substantiate and quantify the declining trend in population size. Therefore, it was judged more appropriate (i.e., less complicated) to use other criteria for the CR classification.

Criterion B. The species' extent of occurrence has declined by at least several hundred linear kilometers in the Yangtze (from approximately 1,700 to no more than 1,400 km; Zhang et al. 2003) and it reportedly no longer occurs in the two large appended lakes (Dongting and Poyang). However, neither its extent of occurrence nor its area of occupancy appears to fall below the threshold level for CR.

Criterion C. The total population (all ages) is certainly less than 250 and therefore less than 250 mature individuals exist. Subcriterion C2 is probably more suitable than subcriterion C1, in that a continuing decline in numbers of mature individuals is projected and all individuals are considered to belong to a single subpopulation (i.e., >90% of mature individuals are in one subpopulation: C2a(ii)). The species therefore qualifies as CR under this criterion.

Criterion D. There is no evidence to suggest that the total population size is as large as 100 and it is probably no more than a few tens of individuals. A precautionary interpretation of the evidence is that there are fewer than 50 mature individuals, and therefore the species qualifies as CR under this criterion.

Criterion E. The viability of the species was assessed at a workshop in Nanjing, China, in 1993 (Ellis et al. 1993, Zhou et al. 1994). However, results were equivocal as rigorous estimates of key parameters (e.g., population size, natural and human-caused mortality rates, intrinsic rate of increase) were not available and therefore the range of possible outcomes was great.

In addition to the above considerations, which justify CR, this species may already be extinct (Possibly Extinct (PE)). The last documented sighting (supported by photographic evidence) was in 2002 and the last confirmed stranding was in 2001 (Turvey et al. in prep.). In November and December 2006 a comprehensive visual and acoustic survey failed to find a single Baiji in the Yangtze River (Turvey et al. in prep.). Two research vessels covered the known habitat of baiji from Yichang to Shanghai in both the upstream and downstream directions (for quadruple coverage). In addition, one vessel towed a hydrophone to listen for Baiji whistles and clicks during the downstream survey. Although Dongting and Poyang lakes were not covered in the 2006 Yangtze mainstem survey, no Baiji have been seen since 2000 by researchers studying Finless Porpoises in those lakes. A few undocumented sightings have been reported since 2004, but there are no photographs or physical evidence for the species? continued existence. The preponderance of evidence indicates that the Baiji is very close to extinction or may already be extinct.