Over 1000 common dolphins recorded on our latest acoustic survey!
COMMON DOLPHINS WERE OUT IN FORCE ON OUR SECOND ACOUSTIC SURVEY AS WE ENCOUNTERED SEVERAL SUPER PODS!
Silurian set out on our latest acoustic survey on the 25th of August to collect crucial scientific data on the whales, dolphins, and porpoises in our waters. For the first time since 2002, our research vessel, Silurian, has been unable to welcome volunteers on board. However, facing the biggest data gap in our history, we determined that we would be able to safely run acoustic surveys with just the crew on board. During these surveys, we tow a hydrophone (underwater microphone) allowing us to detect marine mammals and monitor and record underwater sound. Acoustic data collection is an accurate and consistent way of recording cetaceans and allows us to monitor any changes in underwater noise.
We set off in very different conditions to our first survey. The calm seas and sunshine we had the last trip seemed like a distant memory as we sailed around the north coast of Mull. We anchored that night at Gometra and tucked ourselves away from the howling winds and torrential rain! Luckily, the next morning we awoke to calmer conditions. The action started as soon as we left our anchorage when we were greeted by a superpod of over 200 dolphins! This turned out to be the first of many we would encounter over the course of the survey. They appeared to be feeding as they split off into several groups, with some of them coming into bow ride. You could hear them communicating with each other on the hydrophone with loud whistles and echolocation clicks recorded.
After that auspicious start, the day continued to be incredible for sightings as we sailed west. We encountered several feeding minkes just south of the Treshnish isles, spotted basking sharks as we made our way through Gunna sound, before sailing across the Sea of the Hebrides. The day was topped off by an amazing sighting of white-beaked dolphins, who breached in the distance before approaching the boat for a closer look!
For the next few days we sailed north, with a big swell developing due to strong southerly winds. Although this made spotting marine life much more difficult, we are still able to tow our hydrophone in unsettled conditions and continue to collect valuable data. We continued north as the swell lessened, surveying the waters of the Minch. We had continued to see pods of common dolphins throughout the first week of the survey, but the next day as we sailed towards Loch Inver, we spent the afternoon absolutely surrounded by dolphins! Pod after pod swam past us, coming into bow ride. We recorded over 350 dolphins that afternoon alone!
The weather turned once again as strong winds blew in. We slowly made our way back down to Tobermory, sailing down the Sound of Rassay, before surveying the waters around the Small Isles. The penultimate day saw the most surprising sighting of the trip, with an incredible sighting of a leatherback turtle! True ocean wanderers, sightings of leatherback turtles in UK waters are rare. Read all about the encounter here.
In total, we covered an impressive 596.5 nautical miles (1104.7 kilometers). We collected just under 100 hours of underwater recordings and acoustically identified 192 harbour porpoise, with over 1380 individual clicks.
Tracklines showing where Silurian travelled on our second acoustic survey
Although conditions made it difficult to spot marine life at times, we still recorded 103 sightings of over 1159 individuals. We encountered four species of cetacean, as well as basking sharks, grey and common seals, and of course the leatherback turtle! Common dolphins topped the list, with 41 sightings of over 1000 individuals!!
