Finally, we found our target species. Here are two crabeater seals on an ice floe in the bay to the north east of Wyatt Island. This is a typical sized ice floe, and you can see that it is old ice from last year
This was a good week. Process Site 5 was located in the area of Laubeuf Inlet between Adelaide Island and the Arrowsmith Penninsula. We hoped that this area would contain some seaice, as it is more protected than the more open Marguerite Bay. However the relatively high air temperatures - between +0.2C and 4C - and the high winds - 25-45 knots - have prevented any new seaice from forming, and the only ice in the entire area is large icebergs that have calved from glaciers, and smaller glacier floes and bits. The sea is losing heat, but still contains enough to prevent freezeup. So we searched for seals in back bays and inlets, where we hoped to find floes large enough for seals to haul out upon.
On May 7th, we traveled by Zodiac up the Lawrence Channel to the head of Wyatt Island. During the approach we saw many fur seals hauled out on land, and then started seeing Weddells and crabeater seals on small floes. Since that time, we have noticed that fur seals are a good indicator of the presence of crabeater seals. We were able to land on a small floe (~10 x 12m) and we captured our first crabeater seal of the trip. We attached a satellite tag to the seals head, and collected a suite of blood samples. The use of gas anesthesia went very well (the first time it has been done in the pack ice) and we felt that the day was a success despite several kinks in our handling protocols.
May 8th was plagued by high winds, and we were not able to work. On May 9th, we traveled to the southern tip of Adelaide Island to look for seals and penguins (as there had been no penguins around Wyatt Island). We saw many southern elephant seals hauled out on shore and a few Weddell seals, but no crabeater seals. However, Bill Frasier was able to deploy half of his PTTs on Adelie penguins, so he had a very good day.
May 10th we searched for seals in the area around Pourquoi Pas, Blaiklock, and Ridge Islands. We did not find any seals until we entered Dogs Leg Fjord, which was full of small floes and old glacier bits. The high winds had packed the ice in, so we were not able to make much headway into the bay. We did see 3 crabeater seals, and captured one. However, the floe was small and slightly rotten, so she was able to escape into the water before we had her adequately restrained. We saw no signs of other seals anywhere in the area, and so returned cold, wet, and unsuccessful to the boat.
May 11th we returned to Wyatt Island, and were able to capture and tag two more crabeater seals - an adult male and another adult female. In the morning we saw many seals hauling out on floes, while late in the afternoon most of the floes were empty, but there were many seals in the water. The days are short, but the seals appear to be hauling out in the hours around local noon. In addition to the crabeater seals, we saw many Antarctic fur seals hauled out on floes - reinforcing our idea that where you see one, you see the other species. While the bay was full of ice, the large bergs that had been there on May 7th were gone - which suggests that the winds had cleared the bay and then ice had reaccumulated there. We hope to return to this area at the end of the cruise if we need to deploy more tags.
We have just begun to receive information on the movement patterns and diving behavior of the seals we have tagged. The first seal we tagged spent a few days working along the coast of Arrowsmith Peninsula, and then moved north to the northeast corner of Day Island (the top of Hinks Channel). That area is very similar geographically to the area we have been working (although we have not been there yet), and it looks to be a likely spot to look for seals in the future. Flo's dive data shows that she is spending a lot of time in the water, and making a reasonable proportion of dives between 100-200m. This is the depth where the net tows in the area are finding lots of krill, mysids, and fishes. She also appears to be spending most of her time near shore. As this is where all the remnant floes are, it seems that she is preferentially using areas where there is suitable ice for haulout. Thus it seems that crabeater seals are remaining in areas where there is suitable ice and abundant prey.By remaining in this area and working here, we have been able to document (for the first time) the diving and movement patterns of a seal and the depth distribution and abundance of its prey. This is very exciting, and we are looking forward to following the seals' movement patterns over the next several months.
May 13th we headed for Process Site 4 at the southern end of Marguerite Bay, where we hope to find ice and seals. As the winds have been blowing from the northeast for the last 2 weeks, we think much of the pack ice will have collected in this corner of the bay, so we have high hopes for King George IV inlet.
The seal catching operation as viewed from the bridge of the Lawrence M. Gould. The seal has been drugged, and we are offloading gear from the zodiac onto the ice floe so that we can start work.
Here you can see Steve Trumble with a bag over the head of a crabeater seal. Beth Chittick is administering drugs to the animal using a pole syringe, but she is largely hidden by Steve. You can also see the size of the ice floes we are working on. This picture was taken in Dog Leg fjord.
After sedating the seal with Telezol, we administer gas anesthesia to the animal. First, the animal breathes the gas through a traffic cone placed over it's head (being held in place by Mark Hindell). Once the animal is sufficiently sedated Beth Chittick will place an endotracheal tube into the animal's lungs, so that we can administer gas (anesthesia or oxygen) directly into the lungs.
Here you can see the satellite tag glued to the head of a crabeater seals. In this image, you can also see the endotracheal tube. The seal is recovering from anesthesia, and the tube is about to be withdrawn.
Movement patterns of Flo, the seal we tagged on 5/7/01 with PTT 14750. This is an unedited map of her movements from 5/7-5/11.
Crabeater seals have very unique teeth. The molars have distinct lobes. When the jaw is closed, the seal can force water out of it's mouth and retain the krill. This way it only swallows the food, and not the extra salt water.
The channels and fjords of this area contain high concentrations of krill (pictured to the right), mysids (about the same size as the krill) and fishes. The concentration of prey is highest at the northern end of Laubeuf Inlet and lower at the mouth, but overall the concentrations are much higher here than they were either on or off shelf at Process Site One.
Southern elephant seals on Avian Island,
Antarctic fur seals on Wyatt Island