Unusually high numbers of Blue Whales found south of Iceland

A cruise ship survey conducted by Professor Tom Brereton for the charity MARINElife in late August 2018, with help from the ships Willdife Officer Chris Bielby and other passengers, has found unusually high numbers of the endangered Blue Whale Balaenoptera musculus, the largest animal ever to have lived on earth, in deep North Atlantic waters south of Iceland.

The survey was undertaken on behalf of MARINElife on the Fred Olsen Cruise ship the Black Watch, sailing from Liverpool to Greenland via western Iceland between 17th August and 31st August, with over 3000 km of the cruise route surveyed. There were at least 13 species of cetacean seen over the cruise, but Blue Whales were only seen over one relatively small sea area.

There were 8 confirmed sightings of 14 Blue Whales including a calf, made on two separate days in the Iceland Basin within 150-250km south of Iceland.

Several photographs were taken of the Blue Whales and will be sent off to holders of photo-identification catalogues in Iceland and Canada, in the hope of being to find out where the animals have also been seen.

The Blue Whales, which each need to consume around 1.5 million calories a day, were feeding amongst Fin Whales (the second largest mammal ever to have lived on earth) over a ca250 km stretch of water. A further 17 unidentified Blue/Fin Whales were also sighted in the same areas identified through their whale blows. Based on the ratio of positively identified Blue Whales to Fin Whales, it is possible that a dozen sightings comprising more than 20 individual Blue Whales may have been encountered on the survey.

To put the sightings into context, very few Blue Whales have been seen in these waters before, with the majority of past sightings in the central North Atlantic from west and north of Iceland. Of 7793 geo-referenced sightings in the global GBIF database of Blue Whale sightings, none are from deep waters south of Iceland. GBIF.org (9th September 2018) GBIF Occurrence Download https://doi.org/10.15468/dl.nz9gi6

During North Atlantic Cetacean Sighting Surveys (NASS) which evenly sampled the whole sea area between Greenland and Norway, north to Svalbard and which ran in 1987, 1989, 1995 and 2001 , there were only 83 confirmed Blue Whale sightings from 80,000 km of survey effort - equating to just under one sighting per 1,000 km of trackline surveyed.

The recent sightings in the Iceland Basin are even more surprising given that summer feeding Blue Whales have thought to have shifted north (rather than south in this case) in recent years in the waters bordering Iceland.

It is unknown whether these sightings of Blue Whales in the Iceland Basin form part of an early migration south to wintering grounds, represent a displacement of animals from other traditional feeding areas or if the animals have been overlooked in the past from this area.

Despite a global hunting ban since 1966, the Blue Whale population has declined by 70-90 percent in the past 150 years, with the whale classed as an Endangered Species requiring international protection and conservation measures. Between 10,000-25,000 are estimated to be left in the wild, chiefly in the South Atlantic. In the central and Northeast Atlantic, the population is thought to be around 1000 animals but slowly increasing, with the distribution centred off west Iceland and lesser concentrations between Iceland and Jan Mayen.

The Blue Whale is the largest animal ever to have lived on the planet, growing up to 30 metres in length and weighing up to 173 tonnes. Despite their immense size, there are still major gaps in our knowledge of Blue Whales, especially where they live in our oceans at certain times of the year. The survey has highlighted the potential opportunities and benefits of using cruise ships, ferries and other commercial 'ships of opportunity' (ShOps) to collect valuable data at relatively low cost from little sampled offshore sea areas.

Further details of results from MARINElife whale, dolphin and seabird surveys can be found at www.marine-life.org.uk

Story by Tom Brereton

Tel: 07816 786173 Email: tom.brereton@marine-life.org.uk


Blue Whales seen in the Iceland Blue Whale 19th and 29th August 2018. Photos Tom Brereton

Blue Whale - Tom Brereton 01

Blue Whale - Tom Brereton 02

Blue Whale - Tom Brereton 03

The Blue Whale sightings (blue circles) recorded in August 2018, in relation to past sightings (red circles) obtain from the global GBIF database. GBIF.org (9th September 2018) GBIF Occurrence Download https://doi.org/10.15468/dl.nz9gi6 Image reproduced from the GEBCO world map 2014, www.gebco.net

Blue Whale Map - Tom Brereton