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Offshore Survey Highlights Biodiversity
During a recent marine mammal monitoring expedition, the Hebridean Whale and Dolphin Trust ventured offshore, recording an abundance of marine life in the waters far to the west of the Inner Hebrides.
The Trust’s specialised research vessel, Silurian, took advantage of the rare, extended calm weather in the first week of May to make passage to Stanton Banks; a shallow rocky reef 40 nautical miles southwest of the Isle of Tiree. This rocky underwater landscape of granite ridges up to 160 metres tall protruding from the seabed, criss-crossed by deep gullies filled with coarse shell sand. The strong currents, created by this oceanographic feature, support many species including whales and dolphins.
Over the course of the day: minke whale, common dolphin, common and grey seals, harbour porpoise and a plethora of seabirds were recorded. Two basking sharks – the first reported in the Hebrides for 2017 - were also recorded during the survey transect.
The Trust has long known that the inshore waters of the Hebrides are a fantastic area for marine wildlife, however there is growing evidence that certain offshore waters offer productive habitats for cetaceans – Stanton Banks highlighted as one such area of importance.
Dr Frazer Coomber, Biodiversity Officer at the Hebridean Whale and Dolphin Trust, said, “It’s vital to, when possible, survey these offshore areas which the Trust have started to identify as significant to whales, dolphins and other marine life. Only with continued data collection, can we build a fuller understanding of these areas and the biodiversity present”.
Over the 15 years Silurian has been surveying Hebridean waters, HWDT has managed to visit Stanton Banks on three occasions, including the recent venture on 4th May. The last opportunity was in 2009, when during the passage, five different species of cetacean were recorded including a humpback whale.
Alison Lomax, the Trust’s Deputy Director, adds “Despite the limited coverage of Stanton Banks, this recent survey by HWDT has demonstrated once again that the area is a hot-spot for cetaceans - especially minke whales. However, the Banks are an area which lie outside of any existing, candidate or proposed Hebridean marine protected area for whales and dolphins.”
The monitoring expeditions undertaken by the Hebridean Whale and Dolphin Trust would not be possible without the citizen scientists who join us aboard. These paying volunteers are involved in all aspects of the survey and are trained in how to collect coherent visual and acoustic data.
The Trust’s 2017 survey season started in April, to date Silurian has recorded harbour porpoise, common dolphin, minke whale, common and grey seals and, during the Stanton Banks passage, basking shark. In the coming weeks, Silurian will surpass a total distance surveyed since the monitoring expeditions began in 2002 of 100,000km – the equivalent of sailing around the world 2.5 times!
Western Scotland’s seas are one of Europe’s most important cetacean habitats. With a long, complex coastline, strong ocean currents and a variety of habitats, the Hebrides is one of the UK’s most biologically productive areas. So far 24 of the world’s estimated 92 cetacean species have been recorded in the region – many being national and international conservation priority species.Yet marine ecosystems are fragile, and cetaceans face increasing stress from human activities – including climate change, entanglement, pollution, underwater noise and habitat degradation.
The Hebridean Whale and Dolphin Trust has been monitoring marine mega fauna in the Hebrides since 1994, and from Silurian since 2002. Its surveys are partly funded by a generous grant from Scottish Natural Heritage, which supports the training of future mammal scientists. The charity is the only organisation collecting long-term data on such a large scale on Scotland’s west coast, and its volunteers and scientists have now recorded more than 12,000 cetaceans.