As you probably know if you follow this blog, a team of researchers attached a satellite tag to one of the Southern Resident killer whales a few days ago (Water Ways, Feb. 22). But the transmission stopped sometime after Thursday morning, following three days of transmissions used to track J pod in the Strait of Juan de Fuca and Pacific Ocean.
The researchers, led by Brad Hanson of the Northwest Fisheries Science Center, are now trying to locate J pod during the day to determine whether the tag fell off or simply stopped transmitting.
I received this e-mail from Brad yesterday:
“We have been unable to locate them during daylight hours the last two days. We detected the whales on our towed array on Thursday evening after sunset near the west end of the Strait of Juan de Fuca but we were not able to stay with them until daybreak because they stopped vocalizing and echolocating about 0130 on Friday.
“We spent most of Friday searching the central Strait of Juan de Fuca before heading to Port Angeles late in the evening to avoid an approaching storm. J pod calls were detected off San Juan Island late Friday evening. We are waiting for winds to subside and will resume our search as soon as possible.”
A decision about whether to attach a transmitter to another orca in J pod will wait until the researchers get a look at J-26 to see what may have happened to the transmission. No more than two tags per year may used to track any one pod. Specific whales were selected for tags, generally avoiding females that could contribute to the population.
The ability to track the whales by satellite makes the research work easier, but it does not change the priorities. Figuring out where the Southern Residents travel in winter remains a primary goal of the ongoing research. Two years ago, the crew went to sea looking for the whales without the option of tagging, using the same acoustic equipment being used now to find them.
The cruise also is collecting data on birds, zooplankton and oceanographic conditions, as with the cruise in 2009, Brad told me. The ability to use the satellite data to track the whales allows researchers to collect information along the track where the whales had been.
Without information about the location of the whales, the researchers tend to follow systematic track lines with their research vessel. When the whales are picked up on the acoustic array, the effort to locate the animals takes precedence over data collection. At night, changes in ship speed and heading limits the type and quality of data that can be collected.
The risks of tagging can be debated, and I’ve tried to share the concerns. Still, it is easy to see why researchers wish to have this tool available to them as they try to figure out where the whales go in winter.