Monitoring the Hebrides for 20 Years!
To protect our marine environment, we must first understand it. How do we deepen our understanding…data.
HWDTs flagship, Silurian, celebrated a milestone in 2022 - marking 20 years of monitoring Hebridean seas. Over the decades, more than 1,000 people - or citizen scientists - have joined expeditions on board, making Silurian their home for the duration. Trained by our passionate crew and deployed as field biologists, their hard work gathering data underpins this vital long-term monitoring programme. The data gathered by these citizen scientists has generated one of the largest databases of it’s kind in Europe – with acoustic recordings totalling more than a year’s worth of continuous listening, and visual survey effort equating to sailing the world 3 times over. This colossal database has helped better understand the species found in our waters and is used as evidence to demonstrate how important the west coast of Scotland is for whales, dolphins, porpoises and basking sharks.
2022 FIELD SEASON
18 research expeditions were undertaken in 2022 between April and October. Together with our teams of citizen scientists, we visually surveyed 7,297 km over 128 days, during which time 4,431 animals were recorded from 11 species.
Survey effort was widespread, with more effort concentrated in areas close to the expedition rendezvous points of Tobermory and Mallaig. Areas around the north of the Isle of Mull and the Small Isles also show more coverage (see map below). In 2022, we experienced persistent periods of poor weather for surveying, making it difficult to increase the coverage of the more exposed parts of the Hebrides. Despite this, expeditions covered more ground to the west of the Outer Hebrides compared to 2021. This year’s survey coverage extended between 58.582˚ in the north and 55.524˚ in the south and as far out west to -7.822˚.
2022 visual and acoustic survey effort on Silurian. Effort is displayed on a grid of 100km2 cells (base maps © OpenStreetMap Contributors, openstreetmapdata.com).
SIGHTINGS SUMMARY
During the 2022 season, nine marine mammal species and three fish species were recorded on dedicated visual surveys. Cetacean (the collective for whales, dolphins and porpoises) species recorded, in order of prevalence, were harbour porpoise, common dolphin, minke whale, white-beaked dolphin, bottlenose dolphin, Risso’s dolphin and killer whale. In addition to cetacean species, harbour and grey seals were encountered along with basking sharks, sunfish and yellow fin tuna. In total, there were 1,140 encounters of cetaceans, seals, sunfish, and basking sharks recorded, totalling 4,431 individual animals.
Summary of sightings recorded during the 2022 Silurian survey season
Other notable opportunistic sightings for the year (where the animals were sighted outside of dedicated effort-based visual surveys) include a Sei whale - the first time the species has been recorded from Silurian! - and encounters with John Coe and Aquarius (of the West Coast Community) during two expeditions.
ACOUSTIC UPGRADE
In 2022, there was a significant upgrade made to our acoustic equipment and towed hydrophone arrays. Two new mid-frequency hydrophone elements were added to our acoustic array, alongside our existing high frequency elements. This will allow us to detect sounds at lower frequencies than we were previously able to, whilst still being able to accurately detect high frequency harbour porpoise clicks to determine the number of animals and proximity to the vessel. In addition, we can now gain calibrated recordings of other biological and anthropogenic sounds. The acoustic monitoring element of our survey work is unique and is providing an important resources to study these animals and access changes to the underwater soundscape over time.
Species monitoring is vital to conserve wildlife. Long-term research and monitoring are essential to understand and protect highly mobile and long-led species like whales and dolphins. Silurian has provided the platform for monitoring our seas, but has also been a temporary home for the many people who have joined us on board to undertake the vital data collection.
Thank you Silurian and to everyone who has sailed on her!
Thank you to everyone who joined an expedition in 2022, without you we couldn’t undertake the vital data collection work on board Silurian.
Thank you also to NatureScot who support the data collection programme on board Silurian.
