SIGHTINGS of basking sharks in Scotland have fallen to a 20-year low, but the number of minke whales spotted reached a record-breaking high, conservationists have said.
Basking sharks, which are the world's second-largest species of fish after whale sharks, can be seen off Scotland's west coast between May to October as they breed.
However, Hebridean Whale and Dolphin Trust (HWDT) , who have been carrying out surveys for sharks and other large marine animals for 20 years, only recorded seven sharks last year.
In comparison 2010 was the best year for sightings as HWDT spotted 162 basking sharks and conservationists are now recommending further research to be carried out to understand why the numbers have dropped so low.
Published by NatureScot the survey covered the west coast of Scotland, from Cape Wrath in the north to the Inner Hebrides in the south.
Most of the basking shark sightings were recorded within the Sea of the Hebrides Nature Conservation Marine Protected Area.
Rona Sinclair, of NatureScot, said the recorded sightings might not be a true indicator of the number of basking sharks in Scottish waters as there could be more at a depth not visible to researchers.
She said: “The decrease in basking shark sightings is worrying, and there could be many reasons for this, likely linked to availability of their food, zooplankton.
“However, they may also still be there at depth and just not visible."
She added: “Continued collaboration with researchers is vital, helping us to know how these giant beasts – the world’s second largest fish – are faring, so we can respond appropriately.”
The survey also indicated that the number of sightings of basking sharks and minke whales could be interlinked.
It indicated that when sighting rates for basking sharks are high, they are low for minke whales, and vice versa.
The reasons why are yet to be explained, and the HWDT said more work is needed to analyse the trends over time as there can be factors to take into account like climate change.
Sighting rates of minke whales soared to 1.57 per 100 km last year as the number of them spotted reached a record 167.
Researchers said minke whales migrate to the Scottish seas on the west coast each summer to feed in the country’s rich waters.
They also said despite the encouraging increase in sightings of minke whales, rates of sightings of the whale do fluctuate over time and there are serious issues affecting the vulnerable species.
Conservationists said marine life in Scotland is at risk from human activities including climate change, entanglement, pollution, underwater noise and habitat degradation.
The Trust said ongoing, long-term research is crucial to improve understanding of the impacts, and how best to protect and restore biodiversity.
Dr Lauren Hartny-Mills, HWDT’s science and conservation manager, said: “Scotland’s west coast seas are a global hotspot for cetaceans and basking sharks. Our findings highlight the importance of long-term monitoring of these species and the threats facing them.
“In the face of the nature and climate emergencies, gaining new insights and understanding into what is happening in Scotland’s seas is vital, so we can better protect these remarkable animals and this world-class region of marine biodiversity.”
