Fieldwork on ringed seals and bearded seals complete for the 2011 season
Research scientists Kit M. Kovacs and Christian Lydersen have spent some of their summer weeks in Svalbard, tagging ringed seals and bearded seals with satellite transmitters, as part of the ICE Ringed seals project. This is their field report, where they share their experiences and talk about the early results.
This is a follow-up on the first field report for this season.
We have now set our course homeward-bound, towards Longyearbyen after a very successful field trip. All of the satellite tags we had in our possession for this season are now out operating on seals; 11 on ringed seals and 5 on bearded seals.
The weather has been remarkable co-operative, allowing us to work in the field every single day. Most of our operational challenges have stemmed from dealing with glacier ice. The glaciers in this area are extraordinarily active, calving vast amounts of ice onto the fjord almost continually. It has been a challenge to find little open water areas to set nets without them being full of bergy bits before they have a chance to catch seals or before the next tide shift brings the floating ice back to the little opening.
When we are trying to catch ringed seals we set out 100 m long, 8 m deep nets that are quite light and entangle things easily. They are perfect for ringed seals, but a bit of a pain if a lot of ice or bigger animals hit them. Once the nets are set, it is all about watching and waiting. It is actually a bit boring sometimes, as seal densities are pretty low and it can take many hours or even days sometimes to catch a ringed seal.
Bearded seal capturing is a more active "hunting" mode, which is functioning pretty well these days. We first find a bearded seal that is up on a piece of ice. We then check to see if it has completed it moult. Last year’s worn hair has a very different appearance from shiny, newly grown fur. It is the newly moulted animals that we are after – because we want the glued-on tags to stay in place as long as possible.
If the seal has good fur and has remained in place during our little checking process, we set a net out between two zodiacs a bit away from the seal’s resting place. We then gently pull the net toward the floe at the nose-end of the seal (see picture).
If we manage to get the net in place without losing the seal into the water, we drive up behind the seal quickly with one or both boats, putting the seal into the water – and with some luck the seal strikes the net. But, even if we get a strike, it does not necessarily mean a seal "in the bag". Bearded seals are extremely strong, and even though the nets we use are also very strong, if the seal remains calm and does not roll in the net – it will often simply cut or pull its way out.
But, luckily for us, some roll and then we pretty much have them. This is certainly not the end of the process with this species though. While landing ringed seals is a simple matter of two people pulling the captured animal up into the boat and popping him or her out of the capture net into a bag, bearded seals is a different story just because of their size.
They can weigh over 400 kg, so we need to tow entangled seals to shore between the boats (carefully – so that they are safely held at the surface so that they can always breath when they choose to) and then we must get them up the shore a bit so that we can do the gluing, flipper tagging (for permanent individual identification) etc. The "gluing" in this case involves attaching a new type of GPS-CTD satellite tag developed in collaboration with the Sea Mammal Research Unit, University of St Andrews, Scotland
We do not use any form of anaesthetic with bearded seals to avoid any drug-related risks to them and so that they can be released quickly, fully conscious and ready to go.
They are calm during handling, despite what be a very unusual and somewhat stressful situation for them. The whole capture method works well for these seals, but we end up spending a lot of time untangling and repairing nets after each capture.
Tracking results thus far this season have shown that both the ringed seals and the bearded seals that we have marked in the Kongsfjorden area seem to be sticking tight to the areas where we captured them. This is in marked contrast to results from last year, when the seals immediately headed away on long trips.
A lot of this year’s seals seem to be staying close to the front of glaciers. These areas seem to be rich in food for both seals and sea birds and are collection points for white whales in Svalbard too. This is a concern given that the glaciers are retracting and melting with increasing speed under climate warming.
When the glaciers are reduced to the point where they do not meet the sea, their value will be lost to seals, birds and whales. But, currently they are clearly hot-spots.
The ringed seals we have captured this year clearly show that such locations are providing well for their lucky residents – we have never seen such chubby ringed seals during summer before. Normally they are still pretty slim after fasting in connection with pupping, pairing and moulting. But all of the animals we captured this season have been in fantastic condition – which means FAT for seals.
The different patterns of movement we are seeing between years/areas leave us very exciting about planning next year’s field work so that we can test area, year, age etc. effects.
But – for this season – the seals are now on their own.
Kit and Christian