SUPPORTING ONLINE INFORMATION
1. RECENT BAIJI RECORDS
Recent baiji strandings
1. 18 February 1998: A live baiji was found stranded on the riverbank in Chongming
County, Shanghai after a storm, and was transported to a local rearing pond (figure
S1). Two specialists (Dr Zhang Xianfeng and Zhao Qingzhong) from the Institute of
Hydrobiology visited the pond and confirmed that it was a baiji on 28 February. On 1
March the animal was caught and transported by small boat and car to the Shanghai
dolphinarium, but died upon arrival (figure S2). The animal was an old female, with a
body length of 2.26 m, a maximum body circumference of 106 cm, a neck
circumference of 85 cm, and a weight of c.100 kg. The cause of death was given as
heart and respiratory failure, severe dehydration and starvation. The animal was
preserved as a specimen by the Shanghai Natural History Museum.
2. 14/11/2001: The carcass of a pregnant female baiji was found by fishermen at
Dagang, Zhenjiang City, Jiangsu Province. It was collected and preserved by
Yangzhou University.
Figure S1. Female baiji temporarily held in rearing pond in Chongming County,
Shanghai. Photographed shortly before an unsuccessful attempt to transfer it to the
Shanghai dolphinarium.
Figure S2. Unsuccessful attempt to translocate female baiji from rearing pond to
Shanghai dolphinarium on 1 March 1998.
Recent sightings of live baiji
Date
16/04/2000
17/04/2000
18/04/2000
20/04/2000
22/01/2001
27/05/2001
29/05/2001
29/05/2001
29/05/2001
30/05/2001
23/07/2001
23/11/2001
30/11/2001
05/01/2002
08/03/2002
09/03/2002
14/03/2002
30/04/2002
22/05/2002
02/06/2002
16/12/2002
28/02/2003
- /05/2004
16/07/2004
17/09/2004
- /- /2005
- /03/2006
- /05/2006
Section
Tongling
Tongling
Tongling
Tongling
Tongling
Tongling
Tongling
Tongling
Tongling
Tongling
Tongling
Tongling
Honghu
Honghu
Honghu
Honghu
Tongling
Tongling
Tongling
Honghu
Honghu
Tongling
Tongling
Honghu
Tongling
Honghu
Honghu
Honghu
Number
1
2
2
2
1
1
3
2
1
1
2
1
2
2
2
2
1
1
1
1
2
1
1
2
1
3
1
2
Eyewitness
----------------Fisherman
Fisherman
Reserve staff
------Fishermen
Fishermen
Local Marine Affairs
Administration staff
Reference
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Note 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Ref. 1
Note 2
Note 3
Note 4
Table 1. Reported baiji sightings from 2000 until start of 2006 range-wide survey.
Notes:
1． See figure S3.
2． Data source: Xiong Yuanhui, Honghu (Xin-Luo) National Baiji Reserve staff,
cited in unpublished Honghu Reserve report submitted to Chinese Ministry of
Agriculture, December 2006.
3． A local fisherman observed a baiji less than 100 m from the bank in the Paizhou
area. The animal only surfaced once. Data source: see note 2.
4． Two staff from the local Maritime Affairs Administration observed two baiji
swimming downstream at 100 m distance from the bank in the port area of
Paizhou. The animals surfaced three times and then disappeared. One of the
witnesses had previously visited the IHB dolphinarium in Wuhan and seen the
captive baiji ‘Qi Qi’ before its death in 2002, and so is regarded as a reliable
witness able to distinguish between baiji and finless porpoises. Data source: see
note 2.
Opportunistic baiji sightings were primarily reported to IHB staff by fishermen
employed by the Baiji Monitoring Network in the Honghu National Baiji Reserve and
Tongling Provincial Baiji Reserve. The predominance of baiji records from these two
river sections therefore reflects a lack of monitoring effort elsewhere along the river,
rather than necessarily indicating the absence of baiji in other sections of the Yangtze
after 2000.
During the 2006 survey, a possible sighting of two baiji was reported to IHB staff by
retired schoolteacher Jian Bingzhang, who was doing morning exercises 2-3 m from
the shore at Huangshi Beach Park, Hubei Province, between 0800-0900 on
02/12/2006 with a colleague when he saw two cetaceans swimming downstream. He
stated that the animals were 60-70 m from the bank and 20 m apart, and disappeared
after surfacing three times (Jian himself saw the animal break the surface twice, and
then told his colleague, who saw it surface a third time). The animals were identified
as baiji rather than finless porpoises because both individuals apparently had dorsal
fins. There was no glare interference during the period of the sighting. It is impossible
to evaluate such opportunistic sightings made by non-specialists. However, it is
important to note that several finless porpoises were observed during the 2006 survey
rolling sideways and exposing their pectoral fins; these superficially appeared to be
dorsal fins, making the porpoises resemble baiji on initial viewing even to
experienced observers.
Figure S3. Two photographs of a single baiji in Tongling Reserve on 22 May 2002.
This represents the last authenticated sighting of a baiji in the wild.
2. NOVEMBER-DECEMBER 2006 SURVEY METHODS
Visual survey methods
Two 36 m vessels (KeKao No. 1 and Honghu) surveyed the entire historical range of
the baiji in the main channel of the Yangtze from Yichang to Shanghai, travelling
upstream from Wuhan to Yichang, then downstream to Shanghai and back upstream
to Wuhan. The survey was designed both to maximize the probability of finding baiji,
and to estimate the abundance of the sympatric Yangtze finless porpoise.
Observation stations were approximately 4 m above the river surface on the exposed
roof of the bridge of each vessel and had unobstructed 360º viewing. Vessels
maintained a speed of approximately 15 km/hour and a maximum distance of 300 m
from the nearest bank. Going upstream, KeKao No. 1 covered the north side of the
Yangtze channel and Honghu covered the south side; positions were reversed going
downstream, so that each vessel covered the survey area independently. The two
vessels surveyed roughly the same section of the river each day, but maintained a
separation of approximately 3-5 km, to ensure that sighting probabilities remained
Figure S4. Histogram of total survey effort under different weather conditions during
the November-December 2006 Yangtze cetacean survey.
_____________________________________
independent. When there were navigable channels on both sides of an island or sand
bar, vessels coordinated their efforts to cover both channels (unless only one channel
was navigable); however, the survey trackline was often restricted to the main
Yangtze shipping lane because of regional navigation laws. When sighting conditions
were too poor to allow observation (e.g. due to fog, rain and/or high wind), the vessels
stopped and resumed the survey when conditions improved (figure S4). The boats
were tied together each night, so scientists could meet to discuss the day’s events and
prevent protocol differences from developing.
Each vessel carried two highly experienced marine mammal observers, who acted as
independent observers (IOs), and 5-6 primary observers (POs) with prior experience
in observing finless porpoises and/or other small cetacean species. Observers were
distributed during survey effort in the same configuration on both vessels (figure S5).
-10
left
+10
right
recorder
-90
+90
Figure S5. Areas covered by the primary observers: left observer -90° to +10°, right
observer -10° to +90°, recorder -90° to +90°. The independent observer was
positioned on the raised platform (represented by the square), or on the mounted 25×
Fujinon binoculars (represented by the circle).
POs rotated every 30 minutes through three positions – left observer, data recorder
and right observer – and then rested for 60-90 minutes. 7×50 power hand-held
binoculars were used for surveying, mounted on a 45 cm central wooden staff that
could be held at waist level to reduce fatigue. POs were instructed to constantly scan
their areas primarily with binoculars but occasionally with naked eyes, to minimise
the risk of not detecting cetaceans surfacing close to the survey vessels. At the
beginning of each rotation, the new recorder would record the following information
on the data sheet: time, distance and direction to nearest bank, overall sighting
conditions (poor, fair, good or excellent), observers on watch, and passing or closing
mode (see below). Every 10 minutes, distance to the nearest bank was recorded using
a digital laser rangefinder, and each vessel’s position was recorded using a GPS. Data
sheets and GPS positions were inputted or downloaded to a computer each evening.
When a cetacean sighting was made, the observer estimated distance of the animal(s)
to the vessel and to the nearest bank, angle (read from an angle board), group size,
and coded habitat type. During the rest period the sighting observer completed a more
detailed form for each sighting indicating specific identification features and
behaviour. Distances of groups of porpoises from the vessel and the nearest bank were
estimated by eye, and observers were instructed to practice estimating distances using
the laser rangefinder on the numerous other vessels and buoys on the river, with a
distance calibration exercise conducted every week for all members of the survey
team.
The primary purpose of the IOs was to gather data to allow the estimation of the
probability of detecting animals on the trackline g(0), a critical parameter for linetransect analyses2. Because POs varied in their level of experience, the IOs could also
focus their attention where their greater experience was most needed. Both baiji and
finless porpoises surface briefly and have intervals beneath the surface lasting up to
several minutes3-8, and so having the area ahead of the vessel covered by at least three
observers at all times (i.e., even when the recorder was not looking) was necessary to
maximize the chances that animals are sighted. Sightings by the IOs were recorded in
separate notebooks, and then given to the recorder during a subsequent off-effort rest
period. If IOs thought that a poor estimate was made of group size and their boat was
in closing mode (see below), they could request to suspend the survey effort and
return to the sighting to get a better estimate.
Survey protocol differed slightly for each vessel to maximize the ability both to detect
baiji and to obtain an abundance estimate for finless porpoises. IOs on KeKao No. 1
used only mounted 25× Fujinon binoculars (‘big eyes’) to maximize the ability to
detect baiji at greater distances. Increasing detection distance was needed for sections
of the river that could not be approached closely by either boat and where observers
were unlikely to detect baiji using 7× binoculars. These areas tended to be behind
river bars or up tributaries or side-channels (most of which were non-navigable).
During the first part of the survey from Wuhan-Shanghai, the IOs on Honghu instead
used 7×50 binoculars, and stood on a 20 cm high platform immediately behind the
primary observers. This allowed them to see over the POs, and to calibrate PO
sighting probabilities, but did not appreciably increase the detection distance. During
the second part of the survey, IOs focused their effort on detecting baiji, and spent
time opportunistically scanning tributaries, side channels, and behind river bars as
well as the area from -90° to +90° on the survey trackline. The IOs on Honghu also
switched to using ‘big eyes’.
Although each vessel was instructed to radio the other one if baiji were detected, the
survey design ensured that both vessels were completely independent, i.e. did not cue
each other about sightings. This independence was necessary for an unbiased estimate
of finless porpoise abundance. Vessels traded roles daily, between ‘passing’ (in front)
and ‘closing’ (behind) modes. The closing mode vessel would ‘close’ on sightings
where group size was in question, i.e. suspend effort and spend time with groups of
animals to estimate group size. When the leading vessel had a sighting with a poor
estimate of group size, observers would radio the trailing vessel after they deemed the
sighting to be sufficiently far behind that the second vessel would also have passed it.
This method worked best if observers on the two vessels could still be seen by one
another (within about 3 kilometres), as observers on the leading vessel could judge the
position of the trailing vessel relative to the sighting. Because in previous surveys
baiji had sometimes been observed associating with groups of finless porpoises3,7,9,
the additional time spent obtaining accurate porpoise group size estimates also
provided further opportunity for observers on the closing mode vessel to investigate
whether baiji were also present.
The survey design was broadly similar to the approaches used by Chinese scientists to
count baiji in the past3,9. However, there were some noteworthy differences. The
surveys of the lower reaches of the Yangtze in 1989-1991 involved 4-8 fishing boats
with outboard engines travelling side-by-side at speeds of 7-8 km/hr [ref. 9]. Each
boat had two primary observers described as ‘trained fishermen operators/observers’.
Platform height was not reported but presumably was close to water level on at least
some of the boats. Evidently searching was without the aid of binoculars. The surveys
of the middle and lower reaches (and including both Dongting and Poyang Lakes) in
1997-99 also involved multiple boats – two per section covering 16 river sections
simultaneously – and more than 300 people3. Platform height varied from 2-4 m; the
boats travelled in parallel along opposite sides of the channel at speeds of 8-12 km/hr;
and three trained observers on each boat (at least one of them ‘experienced’) searched
for baiji with hand-held 7× to 10× power binoculars. Mounted ‘big eye’ binoculars,
stick supports for regular binoculars, and a strictly observed rotation schedule to
reduce fatigue were not used in any of these previous surveys. In our 2006 survey the
same two vessels, each manned by a team of experienced observers, carried out the
entire survey, and the platform height of our vessels was equal to that of the largest
boat involved in the 1997-1999 surveys3. In addition, none of the previous surveys
included an acoustic detection component. The only aspect of our 2006 survey
methodology that might be viewed as disadvantageous in comparison to previous
Yangtze surveys is the faster reported vessel speed: 15 km/hr versus 7-8 km/hr [ref. 9]
or 8-12 km/hr [ref. 3].
Comparison of porpoise sighting data from KeKao No. 1 and Honghu indicates that
both vessels independently detected very similar numbers of porpoises in the Yangtze,
both on a daily basis and over the course of the survey (figure S6; tables S2-3). This
close correspondence in porpoise sightings between the two vessels is persuasive
evidence that no baiji were missed in the main Yangtze channel by the survey teams.
Figure S6. Count of daily finless porpoise sightings over the course of the NovemberDecember 2006 baiji survey by KeKao No. 1 and Honghu (excluding porpoises
counted in the mouth of Poyang Lake), showing close correspondence in survey
effectiveness between the two vessels.
Upstream
Downstream
Subtotal
On-effort
PO
185/147
163/162
348/309
Off-effort
IO
58/51
54/68
112/119
Subtotal
243/198
217/230
460/428
29/15
21/13
Table S2. Total numbers of individual finless porpoises seen during the 2006 survey
by the two survey vessels (KeKao No. 1/Honghu).
Upstream
Downstream
Subtotal
On-effort
PO
100/73
76/77
176/150
Off-effort
IO
35/28
34/34
69/62
Subtotal
135/101
110/111
245/212
11/4
10/4
Table S3. Total numbers of finless porpoise sighting events during the 2006 survey
by the two survey vessels (KeKao No. 1/Honghu).
Acoustic survey methods
One vessel also carried a full-time acoustic survey team consisting of two on-effort
researchers using a towed hydrophone (C54XRS with 87 m cable, Cetacean Research
Technology). The acousticians listened continuously for potential baiji whistle signals
in real time for the entire duration of the survey. An acoustic baiji database, obtained
in 1996 from a translocated free-ranging female baiji held in the Tian’e-Zhou
National Baiji Reserve, demonstrates whistle signals with a frequency range between
3.8 kHz and 6.8 kHz (figure S7, Electronic Appendix Audio File) [ref. 10]. We
monitored the frequency band from 4-6 kHz to focus on the fundamental frequency
component of the baiji’s whistle, using a band pass filter (NF3611) to eliminate
background noise. The whistle’s source level calculated by ref. 10 was 143.2 dB rms
re 1 uPa (s.d.=5.8). This amplitude was approximately 50 dB higher than the band
noise level when towing low frequency hydrophones on the downstream portions of
the survey. Under these ambient conditions, the detection distance of a baiji whistle
was estimated to be 300 m, assuming simple omni-directional/spherical sound
propagation. However, when travelling upstream the background noise level was only
10-20 dB higher than baiji source levels, because of the higher relative speed of the
vessel against the water current in the river.
Figure S7. Sonogram of whistle of a free-ranging baiji recorded in 1996.
The acoustic baiji database indicates that the animal recorded in 1996 produced
whistles with an average silent interval of 205 s (s.d.=254). Assuming a constant
speed of 15 km/hour, the survey vessel travelled 854 m during this time interval, and
the maximum detection range from the hydrophone was 300 m in any direction. This
means that the acoustic monitoring system would have been able to detect
approximately 70% of the baiji encountered directly on the survey trackline.
However, as the width of the river varied from several hundred metres to a few
kilometres, the overall coverage probability across the baiji’s historical range in the
main Yangtze channel would have been substantially lower than 70%.
References
1. Braulik, G. T., Reeves, R. R., Wang, D., Ellis, S., Wells, R. S. & Dudgeon, D.
Report of the workshop on conservation of the baiji and Yangtze finless porpoise.
Baiji.org Foundation, Zurich (2005).
2. Buckland, S. T., Anderson, D. R., Burnham, K. P., Laake, J. L., Borchers, D. L.
& Thomas, L. Advanced distance sampling: estimating abundance of biological
populations. Oxford Univ. Press (2004).
3. Zhang, X., Wang, D., Liu, R., Wei, Z., Hua, Y., Wang, Y., Chen, Z. & Wang, L.
The Yangtze River dolphin or baiji (Lipotes vexillifer): population status and
conservation issues in the Yangtze River, China. Aquatic Conserv.: Mar. Freshw.
Ecosyst. 13, 51-64 (2003).
4. Zhou, K. & Li, Y. Status and aspects of the ecology and behavior of the baiji,
Lipotes vexillifer, in the lower Yangtze River. Occ. Papers IUCN SSC 3, 86-91
(1989).
5. Hua, Y., Zhao, Q. & Zhang, G. The habitat and behavior of Lipotes vexillifer.
Occ. Papers IUCN SSC 3, 92-98 (1989).
6. Liu, R., Yang, J., Wang, D., Zhao, Q., Wei, Z. & Qang, X. Analysis on the
capture, behavior monitoring and death of the baiji (Lipotes vexillifer) in the
Shishou semi-nature reserve at the Yangtze River, China. IBI Reports 8, 11-21
(1998).
7. Würsig, B., Breese, D., Chen, P., Gao, A., Tershy, B., Liu, R., Ding, W., Würsig,
M., Zhang, X. & Zhou K. Baiji (Lipotes vexillifer): travel and respiration
behavior in the Yangtze River. Occ. Papers IUCN SSC 23, 49-53 (2000).
8. Akamatsu, T., Wang, D., Wang, K., Wei, Z., Zhao, Q. & Naito, Y. Diving
behaviour of freshwater finless porpoises (Neophocaena phocaenoides) in an
oxbow of the Yangtze River, China. ICES J. Mar. Sci. 59, 438-443 (2002).
9. Zhou, K., Sun, J., Gao, A. & Würsig, B. Baiji (Lipotes vexillifer) in the lower
Yangtze River: movements, numbers threats and conservation needs. Aquat.
Mamm. 24.2, 123-132 (1998).
10. Wang, K., Wang, D., Akamatsu, T., Fujita, K., Shiraki, R. Estimated detection
distance of a baiji's (Chinese river dolphin, Lipotes vexillifer) whistles using a
passive acoustic survey method. J. Acoust. Soc. Am. 120, 1361-1365 (2006).