DETECTION OF YANGTZE FINLESS PORPOISES IN THE POYANG LAKE MOUTH AREA VIA PASSIVE ACOUSTIC DATA-LOGGERS - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 348

Date

2007-7-17

0:53:30 0:53:32 0:53:34 0:53:36

50
40
30
20
10
0

100

50

0

-50

-100

160
120
80
40
0

Figure 2. Sound pressure (SP), travel time difference (Td) between two hydrophones of each A-tag, and
interclick interval (ICI) of typical porpoise click trains recorded by the stereo acoustic data logger (A-
tag). Note that the sound pressures and ICIs of porpoise click trains were changing smoothly.

Date

2007-7-12

16:46:15 16:46:20 16:46:25 16:46:30

40
30
20
10
0

100

50

0

-50

-100

160
120
80
40
0

Figure 3. Sound pressure (SP), travel time difference (Td) between two hydrophones of each A-tag, and
interclick interval (ICI) of typical cargo ship noise recorded by the stereo acoustic data logger (A-tag).
Note that the sound pressures and ICIs of porpoise click trains were changing randomly.

For the boat-based acoustic observations at Stations 0, 1, and 2, owing to the immobility
of the relative direction between the two hydrophones of each A-tag and the current direction,