Mar 20 - Groundhog Day!
Noon Position : lat 58 41.2 S, long 51 25.9 W
Course made good: Variable
Air temperature @ noon today : 2.2 degrees C
Sea temperature @ noon today : 2.5 degrees C
Wind: Direction N, Force 6
Have you ever seen the film Groundhog Day? Well, just at the moment I feel a bit like that! Currently we are doing Swath Bathymetry in an unidentified piece of ocean just between the Drake Passage and the Scotia sea. On the charts it doesn't have a name and we are doing transects, lines up and down this blank piece of ocean, of course, once we have done the transects we will have some very pretty pictures of it, putting it on the map quite literally. But at the moment we get up each day and the same people are looking at the same view and having similar conversations. It is really quite surreal. Every so often I have to pinch myself to remember that we are in a subantarctic zone. Normal everyday life is watching the waves and the weather (the fog has come back), doing scrub out on Sunday and watching the evening film. But normal is also watching the albatross wheeling about the ship, counting the icebergs we pass in each watch and being surprised by a dozen hourglass dolphins and a pilot whale diving under the bow of the ship. I think I will take this version of normal any day.
The Scotia Sea is an important area for a large proportion of the world’s whales, and includes many populations that were severely depleted by the whaling industry in the first half of the 20th Century. The estimated biomass (total weight) of whales is believed to be 10% of what it was before whaling began. In 1994, the International Whaling Commission named the majority of the Southern Ocean as a sanctuary in which all commercial whaling is prohibited.
Even nowadays little is known about the foraging behaviour and movements of whales in relation to their environment in the Southern Ocean. This is largely due to the fact that whales spend most of their time under water so are difficult to observe, because ship time can be prohibitively expensive, and also as weather conditions are often too poor, especially in the winter. Whales are at the top of the food chain so there may be many factors that affect their distribution. Thus there is now a need to monitor whale populations and to understand the role that different species play in the Southern Ocean ecosystem.
The aim of the two marine mammal biologists, Debbie Salmon and René Swift, is to improve our understanding of these animals in the Scotia Sea and around South Georgia using both passive acoustic and visual survey techniques. As well as whales, we also record the presence of other marine top predators including dolphins and seals.
Marine mammals are voluntary breathers, meaning that they have to return to the surface to breath, and it is when they are at the surface that we can observe and count them. However they are typically only at the surface for a few seconds, and can be difficult to sight especially during rough weather or in fog. To improve our chances of detecting the visual cues that marine mammals produce (blows, splashes, footprints and sometimes the animals back) we observe from the “Monkey Island” the highest deck on the ship at 19m above sea level, which on a clear day means that we can observe over a distance of 9 nautical miles. To aid identification we use 7x50 binoculars, and each scan an arc 90 degrees ahead of the vessel. When a whale is sighted we record the angle of the whale from the trackline and it’s distance from the vessel using reticulated binoculars. We record this information together with information on environmental conditions which may affect our ability to sight animals, such as sea state, onto a laptop computer running Logger 2000 . These data are used together with a statistical method called distance sampling to estimate population sizes for the areas of ocean that we cover (for further information on distance sampling visit the Distance website
Since sailing on the 15th March the weather has been good enough to allow us about 47 hours of visual observations. So far we have seen at least five different species of whale, two species of dolphin and one species of seal. These include southern right, fin, sei, and minke whales, which are baleen whales and were all targets of commercial whaling. We have also seen toothed whales/dolphins, including southern bottlenose whales, pilot whales, and hourglass dolphins. Sometimes we are not able to identify the species of whales that we see, particularly for beaked whales that are often discrete and are therefore amongst the least studied of the whales.
Marine mammals live in a medium where sound travels further than light and thus have evolved to use sound in all aspects of their lives from prey capture (echolocation) to communication. Although marine mammals are not obligatory vocalisers all produce sounds sometime during their lives. Sperm whales produce sounds (clicks) 75% of the time they are submerged, while in other species, such as the fin whale, it is thought to be only the male that vocalises and then only during the breeding season. Sound thus allows the researcher another tool by which they can study both the distribution and behaviour of marine mammals, one that is less affected by the weather and one that often has increased detection ranges over visual surveys.
Marine mammal vocalisations cover a wide range of frequencies from the infrasonic pulses of the blue and fin whales below 20Hz, to the whistles and clicks of sperm whales and some dolphins in the audible range (20Hz-20kHz), up to the infrasonic clicks of the harbour porpoise (135kHz) or white-beaked dolphin (250kHz). To cover this diverse frequency range scientists employ a wide variety of recording devices including the sonobuoys and pop-ups that we will be deploying during the course of this cruise.
Sonobuoys are disposable hydrophones (underwater microphones) that transmit their signal back to the ship via VHF radio signal (figure 1), this is picked up by modified broadband communications receiver and recorded to hard disk. Sonobuoys were designed by the military for tracking submarines and are sensitive to low frequency sounds making them ideal for recording the low frequency sounds produced by the larger baleen whales, e.g. the 20pulses produced by fin whales (20-28 Hz), right whale moans and groans (80-120Hz), and humpback song. Sonobuoys are deployed opportunistically when large groups of whales are sighted, or at designated hydrographic stations. So far this trip sonobuoys have been deployed three times and have recorded fin whales (figure 2) and a Blue Whale down sweep.
Figure 1. Fin whale 20Hz pulses. X axis Time (minutes), Y axis Frequency (Hz), the Greyscale shading represents sound intensity. Spectrogram created in Raven v1.2.
Listen to the fin whale 20Hz pulses at x10 normal speed. (Click Here)
Listen to Blue Whale downsweeps at x10 normal speed. (Click Here)
Pop-ups are autonomous recording packages (ARP’s) that ‘pop’ back to the surface once they have finished recording. Pop-ups were designed and built by the Bioacoustics Research Program (Cornell Laboratory of Ornithology ) and have been deployed throughout the world to record the sounds from the larger baleen whales. During this trip we will deploy 4 pop-ups in the western core box off South Georgia, two of the units will deployed as part of BAS’s Long Term Monitoring Program’s ADCP moorings. Two further units will deployed close to Bird Island to record the Southern Right Whale population that uses the bay there. In the long term these units will provide much needed information on the winter distribution of whales off South Georgia and how they interact with their physical and biological environments.
Whale-watching was written by Rene and Debbie when they were warming up inside.
We had a very sociable port call in Stanley earlier this month. Not only was it a four day call, but the Ernest Shackleton was also in port. She was calling in for a crew change before her last call to Rothera. This gave us the opportunity to have a look around both ships, meet up with friends and go out for a drink together.
I was lucky enough to have a couple of days free whilst we were in the Falkland Islands and I grabbed the opportunity to jump on a plane and fly to the West Falkland. I visited Port Howard, which is the main settlement of the West Island. There only 85 people on the whole island and half of them live in Port Howard. This bustling community was having the annual golf championships the day after I arrived. The golf course is quite challenging with more heather and bog than the average, although I am told that the greens are superbly looked after by Rodney. As well as golf, the West Falkland is very popular with fishermen. I was sharing the Lodge with three Scots who were very excited about their catch of 23 whoppers and didn't once mention 'the one that got away'. I managed to avoid both golf and fishing and went walking in the nearby hills. The West is hillier then the East and the ranges are more compact making for good days out.
Back in Stanley again and the weather was sunny and not windy, a very rare occurence. Tom (Elliott) persuaded Nick (Dunbar) and I to bike out to Cape Pembroke lighthouse with him. Nick borrowed a bike and despite the entertainment of Tom and I falling into the sand spent the whole ride suffering. Apparently the saddle was just a bit too razor sharp and it felt like he was being cut in half. After walking for a while and swapping bikes a couple of times we all made it safely there and back, but Nick was walking like a cowboy for the rest of the port call!
So by the end of this week we will have finished this part of the swath cruise and be on our way to Signy. It will be good to catch up with friends and help to close the base that we opened at the beginning of the season.
Thankyou to all the friends and family who wrote to ask where the web page was and why it hadn't appeared on the web yet?! It is nice to know that people are watching out for us!! Til next week....bye.