Seismic sources and marine wildlife
Race to save 100 stranded whales on New Zealand beach – BBC
Whale rescue: Hope for surviving whales ‘slowly slipping away’ on Farewell Spit – NZ Herald
As reports that hundreds of pilot whales have become stranded on a remote New Zealand spit hit the headlines, people around the world are struggling to understand, Why? Anthropogenic pollution (noise or some other potential sensory disabler) or unfathomable natural phenomenon?
With multiple examples of similar strandings in recent years, this is not the first time that we at Geo ExPro have looked at the possible affects on Cetaceans and other marine wildlife, resulting from oil and gas industry activity. The extract that follows (from a longer article, link below), on the potential for disturbance to the marine realm resulting from seismic data acquisition, address’ that very issue.
Marine Seismic Sources Part IV
by Lasse Amundsen and Martin Landrø
Every year thousands of whales beach themselves. Multiple strandings in one place are rare but when they happen they often attract media coverage as well as rescue efforts.
Visual representation of song sung by the Northern minke whale, produced by Mark Fischer, who converted the sound frequencies of the whale song into a graph using a mathematical process. (AGUASONIC ACOUSTICS/SCIENCE PHOTO LIBRARY)
The whales that most frequently mass strand are toothed whales, which normally inhabit deep waters and live in large, tightly knit groups. Their social organization appears to be a key factor influencing their chances of mass stranding, as, if one gets into trouble, its distress calls may prompt the rest to follow and beach themselves alongside.
However, many other, sometimes controversial, theories have been proposed to explain stranding, but the question as to why they do remains unresolved.
Naval activities, such as live ammunition training, vessel noise and explosions, introduce noise into the oceans. However, the naval activity that has been subject to the most scrutiny is mid-frequency sonar, which can produce sound at levels of up to 237 dB re 1uPa @ 1m at frequencies between 2-8 kHz.
A controversial issue is the extent of the relationship between sonar operations in nearshore areas and the relatively rare stranding of beaked whales.
Sonar operations have been correlated temporally and spatially with strandings of 14 beaked whales in the Bahamas in 2000, but why these whales actually swam onto the beach is not understood.
(You can read the full article here – Marine Seismic Sources Part IV)
While the exact reasons for whales becoming beached in this way is unclear, this video may provide some answers.
Steve Whitehouse of whale-rescue.org describes how the whales get stranded. (Source: NZ Herald)
References
Race to save 100 stranded whales on New Zealand beach – BBC News
Whale rescue: Hope for surviving whales ‘slowly slipping away’ on Farewell Spit By Sam Hurley, Lynley Bilby NZ Herald
VIDEO: Whale stranding at Farewell Spit – NZ Herald
From Geo ExPro
Marine Seismic Sources Part IV by Lasse Amundsen and Martin Landrø
The 1956 documentary The Silent World by Jacques-Yves Cousteau wowed audiences with its vibrant depiction of aquatic life. But the Silent World is far from silent. This article appeared in Vol. 7, No. 5
