Density of two months of large commercial vessel traffic in the sanctuary, with peak densities seen in the shipping lanes
“Thrilling” is not a word I thought I would ever use in describing an Acoustical Society meeting, but there were moments last week that bordered on just that. Driving this is an intersection of rapidly increasing computer processing power and advancing sensor technologies – put in the hands of some of the nimble intellects that are making up the current crop of bio-acoustic post-docs.
Over the five days of the meeting there were many sessions on “Passive Acoustic Monitoring” (PAM) which presented many of the aspects of putting sensors in the ocean, collecting the data, and then making sense of it all. In practice this often means collecting the vocalizations of whales or dolphins over a period of time and watching the population dynamics change as a consequence of environmental conditions.
The output of these studies can be time-compressed animations of the peregrinations of dolphin schools or whale pods,[i] or in the case of Chris Clark, the acoustical impacts of ship traffic on humpback, fin and right whales.[ii] Dr. Clark’s animated display was a stunning “spatial-temporal” graphic of the changes in the hearing and communication range of these three whale species as a cargo ship passed over their habitat. I will make these graphics available on the OCR website once I get them from Chris, but meanwhile you can find out about the program here: http://stellwagen.noaa.gov/science/passive_acoustics_noise.html
Another telling presentation by Manolo Costellote came from his PAM study of the seasonal migration of fin whales in the Mediterranean Sea over a three year period. During one of the seasons there happened to be a concurrent seismic airgun survey. The monitoring clearly demonstrated that the whales avoided their traditional winter feeding areas throughout and even after the survey. This indicates the acoustical impacts of airgun surveys reach over hundreds of kilometers for these animals.
Of course Manolo wanted to know where the surveys were taking place, and something about the sizes of the airgun arrays. He managed to locate the company doing the work, but they were predictably uncooperative. Not to be discouraged, he did a little sleuth work and found a “blog” of one of the crew members, which included the entire equipment list; airgun capacities, photographs of the ship, and pretty much everything he needed to calibrate his findings except for the exact locations of the survey (which he derived through some clever data evaluation).
It is work like this which may eventually put the current practices of airgun surveys “on the ropes” until the oil industry can find more benign ways of locating offshore oil.
Many other breakthroughs were presented and new ideas introduced over the course of the week across the field of acoustics. While overall the meeting was still pretty high on the “pencil-pocket” index, our field of marine bioacoustics is going through a thrilling sea change.
Stay tuned!
[i] Kaitlin E. Frasier “Acoustic tracking of whistling dolphins offshore of Southern California”
[ii] Christopher W. Clark “Result ad insights from operational monitoring networks”