Wednesday, August 12, 2009

the mystery clicks

Today dawned calmer than predicted. In our efforts to find workable seas over the past few days, we have moved out of the area surveyed for whales last year. This morning we started heading back to the hot spots in the areas surveyed last year and during the earlier parts of this cruise, listening and watching for whales, with a course that we hoped would cover favorable habitat for beaked whales. Many who study the distribution of beaked whales have noticed that not only do beaked whales favor areas where the bottom is 1000m deep, they also seem to congregate in submarine canyons or seamounts. Our course took us in deep water past several sea mounts. In the early afternoon, the acoustic monitors started picking up faint clicks like those of beaked whales in the direction of the seamount where beaked whales had been detected on a survey track last year. When they noticed that there appeared to be several whales clicking at the same time, we diverted the ship to the area, pulled up the hydrophones for maneuverability, and maneuvered the ship for optimal sighting of where the clicks were detected. The sighting conditions were excellent, yet the observers did not sight any beaked whales at all. Beaked whales can dive for more than an hour, but in a concentration, some whales should certainly have surfaced at that time. In deciding whether to continue to wait or to move on, we noticed that our depth was shallower than optimal for beaked whales. We therefore decided to move directly into deeper water where concentrations of whales were sighted last year. As we reached this area, around 6:30 PM, the visual observers sighted several groups of beaked whales and the acoustic team heard clicks from at least one foraging dive. We approached toward the groups, recovered the hydrophone arrays for maneuverability, and once we got close, we deployed the tagging boat. For some reason on this cruise, the tag boat keeps getting deployed late in the day even though we start at sunrise! The visual team noticed calves in several of the groups and was able to position the tag boat near surfacings of a group that did not have a calf in it. However, we were not able to get the tag boat close enough to attempt to tag before the whales appear to have made a deep foraging dive. The daylight did not hold out for us to be able to follow the whales and attempt tagging later.

Today’s efforts reinforce again how difficult it is to tag a beaked whale. You have to find animals, select a promising group, get an idea of their behavior and movement patterns and get a small boat within a few hundred meters of a group of whales coming up from a 15+ minute dive, when the whales could move more than a few hundred meters.