Passive Acoustic Monitoring (PAM) is a growing area of
cetacean research, referring to the use of hydrophones (underwater
microphones) to detect and monitor the presence of vocalising marine
mammals.
An introduction to PAM
Cetaceans
produce a wide variety of vocalisation types, ranging from the low frequency
(15-2000 Hz) calls of baleen whales, to the impulsive broadband 'clicks'
produced by sperm whales (peak frequency c.6-16 kHz) and dolphins (peak
frequencies of c.10 to 130 kHz), tonal 'whistles' produced by many dolphin
species (frequencies of 2 to 80 kHz), and the high frequency (peak frequency
c. 130 kHz) echolocation clicks of the harbour porpoise. The type of
hydrophone system required therefore depends on the species being monitored,
and it is sometimes necessary to incorporate several different systems
during a single survey, for example for surveys wishing to monitor both
dolphins and porpoises in UK waters. PAM is a particularly useful research
tool in deep-water offshore regions when the weather is often adverse for
visual detection of cetaceans.
Using PAM for research
PAM is used as a research tool by many organisations to
assess the presence of cetacean species in an area. Our expertise in this
region has included use of a towed high frequency hydrophone array to
monitor harbour porpoises in the Shetland Islands and the Netherlands, and
the use of standard mid-frequency Seiche and Ecologic towed arrays to
monitor sperm whales, dolphins and other toothed whales in the Rockall
Trough, Bay of Biscay and Moray Firth. Analysis of acoustic data using a range
of software is also carried out by Ketos Ecology, particularly
focusing on sperm whale codas and dolphin whistles.
Using PAM for mitigation
The
use of PAM is increasingly recognised as a potential monitoring tool when
mitigating the effects of anthropogenic sound (such as airgun and military
sonar sound) on marine mammals. Ketos Ecology has operated most of the
standard PAM systems currently utilised by industry, including the towed
hydrophone arrays developed by Jonathan Gordon/IFAW/Ecologic and by Seiche,
and relevant software including Pamguard, CoolEdit2000, SeaPro, Ishmael, Rainbow Click
(IFAW), Whistle Detector (shown here with call from long-finned pilot whale)
(IFAW), Porpoise Detector (IFAW) and Logger (IFAW).
Cetaceans
produce a wide variety of vocalisation types, ranging from the low frequency
(15-2000 Hz) calls of baleen whales, to the impulsive broadband 'clicks'
produced by sperm whales (peak frequency c.6-16 kHz) and dolphins (peak
frequencies of c.10 to 130 kHz), tonal 'whistles' produced by many dolphin
species (frequencies of 2 to 80 kHz), and the high frequency (peak frequency
c. 130 kHz) echolocation clicks of the harbour porpoise. The type of
hydrophone system required therefore depends on the species being monitored,
and it is sometimes necessary to incorporate several different systems
during a single survey, for example for surveys wishing to monitor both
dolphins and porpoises in UK waters. PAM is a particularly useful research
tool in deep-water offshore regions when the weather is often adverse for
visual detection of cetaceans.
The
use of PAM is increasingly recognised as a potential monitoring tool when
mitigating the effects of anthropogenic sound (such as airgun and military
sonar sound) on marine mammals. Ketos Ecology has operated most of the
standard PAM systems currently utilised by industry, including the towed
hydrophone arrays developed by Jonathan Gordon/IFAW/Ecologic and by Seiche,
and relevant software including Pamguard, CoolEdit2000, SeaPro, Ishmael, Rainbow Click
(IFAW), Whistle Detector (shown here with call from long-finned pilot whale)
(IFAW), Porpoise Detector (IFAW) and Logger (IFAW). 
