The first estimate of abundance based on quantitative survey data (1979-81) was made by Zhou (1982), who guessed that there were only about 400 animals all told. On the basis of surveys conducted in 1985-86, Chen and Hua (1989) made an educated guess that the total population was around 300. Surveys by Zhou and Li (1989) between 1982 and 1986 suggested that there were 100 baiji in a 770 km segment of the lower Yangtze from Hukou to the river mouth, compared with 78 to 79 dolphins counted by Chen and Hua (1989) in the same segment in 1985-86. Repeated surveys of a 500 km segment of the lower Yangtze (Nanjing-Hukou) in 1989-91 produced a maximal count of 12 individuals, leading Zhou et al. (1998) to infer a total abundance of about 30 baiji in that river segment. Those authors reasoned that if the species still inhabited its historical range of about 1,700 linear kilometers of river, with a density similar to that found in their study area, the total population in the early 1990s would have been only about 100. Attempted comprehensive surveys of the entire species' range in 1997-99 resulted in a maximal count (November 1997) of 13 dolphins (including one calf), leading to the generally accepted view that abundance had continued to decline and that the total population was by that time very small. The sighting rate in the three years of surveys declined at an annual rate of about 10% (Zhang et al. 2003). Informed guesses in the early 2000s were that there could be only "a few dozen" (Zhou 2002) and "very likely ? less than a hundred" (Reeves et al. 2003) baiji left (also see Wang 2000, IWC 2001, Zhang et al. 2003). Although no credible time series of counts or abundance estimates is available to provide a rigorous evaluation of trends, there is an overwhelming consensus that the baiji population declined rapidly over the past several decades.

During surveys in the late 1990s baiji were found mainly in several segments of the Yangtze between Tongling and Dongting Lake, such as the Tongling section, the Poyang Lake mouth area, and the Honghu section (Wang 2000, Zhang et al. 2003).

More recent evidence suggests that this species might already be extinct. 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 might already be extinct.

Unknown