basking shark

 

Sightings of basking sharks off the Scottish coast have hit their lowest level in 20 years, conservationists report.

These gentle giants, the world’s second-largest fish species after whale sharks, typically gather off Scotland’s west coast from May to October to feed on plankton and breed.

However, only seven basking sharks were recorded in 2023 by the Hebridean Whale and Dolphin Trust (HWDT), which has been surveying the area for two decades.

This figure marks a stark contrast to HWDT’s best year for basking shark sightings in 2010, when 162 sharks were observed.

The trust is now calling for further investigation to understand the significant decline in sightings last year.

The survey covered a wide area of Scotland’s west coast, ranging from Cape Wrath in the north to the Inner Hebrides in the south. Most sightings in 2023 occurred within the Sea of the Hebrides Nature Conservation Marine Protected Area.

Rona Sinclair, of NatureScot, 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.”

A similarly low number of basking sharks were recorded by HWDT in 2022, raising further concerns.

Given that basking sharks are an endangered species, growing up to 10 meters (33 feet) in length, the need for more analysis is urgent.

These sharks, which feed on microscopic plankton using their large mouths, migrate between Scotland and the warmer waters near Madeira and the Canary Islands.

Historically, basking sharks were hunted in Scottish waters until 1994 for the oil in their livers, which contains squalene, a valuable component used in industrial lubricants, cosmetics, perfumes, and artificial silk.

While basking shark sightings dropped, HWDT recorded an increase in minke whale sightings in 2023. The trust noted an inverse relationship between basking shark and minke whale sightings, although the reasons remain unclear.

Potential causes, including climate change, are under investigation.

Dr Lauren Hartny-Mills, of HWDT, said: “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.”

 

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