29 July 2013
Aboard the Henry Bigelow, Days 5-6
Although the end of our cruise brought a lot of nasty weather, which really inhibited the visual survey effort, we did have some good luck with our passive acoustic efforts. We have been towing a hydrophone array 300 meters (~900 feet) behind the ship, listening for anybody who is talking underwater. Yesterday, we ran a transect that crossed over some sites where we had previously seen beaked whales, and lo and behold – we picked up several individuals on our hydrophones! Some of the echolocation clicks we heard belong to Cuvier’s beaked whales, one of the more studied among the beaked whale species. But then we got some clicks that we didn’t recognize, which was pretty exciting!
We can track individual animals by their echolocation clicks to see how far they are from the vessel. The difference in the time that their clicks are received at one hydrophone versus another allows us to calculate the direction that the clicks are coming from. The image on the top below shows the bearing (or direction) for several animals over time. The blue squares are several sperm whales that were foraging in the area, and the broken black line is from beaked whales! The spectrogram on the bottom shows the characteristics of one of the beaked whale clicks – in this case, showing a strong upsweep.
It’s hard to believe that our survey is over already. The scientific crew (17 of us in total) and the ship’s crew (21 on the boat) have been great and it’s been a pleasure to work with all of them. Hopefully we’ll be able to come out here again next year!