Speaking to CNN, professor of biology Adam A.Peck at the University of Hawaii says that the whale hunted by Hvalur hf on Saturday night is a blue whale and not a hybrid blue/ fin whale as believed by Icelandic experts.
"It is like a fin whale, it behaves like a fin whale, but after you shoot it you notice [the characteristics] are different to a fin whale".
Iceland resumed commercial whaling in 2006. "Photographs point to the fact that it's a hybrid whale and we're nearly certain that it is one, but we can't be sure until autumn when we get it DNA tested".
Loftsson's whaling station crew posed for photos next to and on top of the whale.
Dr Phillip Clapham from NOAA Alaska Fisheries Science Centre said: "It has all the characteristics of a blue whale; given that - notably the coloration pattern".
'From the photos, it has all the characteristics of a blue whale; given that - notably the coloration pattern - there is nearly no possibility that an experienced observer would have misidentified it as anything else at sea'. "There are a lot of blue whales off the Iceland coast, when we see the blows and sail to it, and we realize it is a blue and then we leave it and go and look for fin whales".
"Whale 22 (documented by us on July 7th midnight / July 8th early morning) shows features of a blue whale (darker belly, all black baleen, bluish colour)", they wrote in a Facebook post.
"This bad incident comes as Japan is rumoured to be planning an attempt to overturn the global moratorium on commercial whaling, and clearly speaks to how utterly inappropriate it is for countries to even contemplate allowing a large-scale return to this grossly inhumane and haphazard industry". One has not been slaughtered for more than 50 years.
Sea Shepherd, another conservation group, claimed Wednesday that the dead whale was a blue whale as evidenced by experts they've spoken to and experience with the world's largest animal.
No blue whales have deliberately been caught since 1978, the International Union for the Conservation of Nature reports. Prior to the catastrophic commercial whaling of the 20 century it is estimated that there were in the region of a quarter of a million blue whales, but their populations crashed in the 1950s and 60s.