Few other animal species on Hardangervidda have been as much the focus of scientific research as the spotted trout. The spotted trout is considered to be a genetic variant of brown trout. It lives in parts of the Krækkjav water system. Otherwise, on a world scale, this species is only found in a small area in Kaukasus, and possibly also in a lake in Rondane.
After the ice age, Granvin Fjord reached all the way up under Skjervsfjossen waterfall. Just a thousand years later, as a result of the rising of the land after the ice melted, this whole inner part of the fjord freed itself of the sea and became Granvinsvatnet lake. In spite of this rise in elevation, this waterway is still navigable for fish: Sea trout have wandered into Granvinsvatnet in more recent times and evolved to become freshwater trout. And salmon and sea trout made the journey 13 kilometres up the Storelvi river.
He wondered, surely, the fisherman who in 1769 found a 3.3 metre-long silvery shining sea creature at Glesvær. Perhaps he hadn't heard the legend about the sea snake. If so, he must have thought that that was what he had found, for the sea creature resembled more a fantasy figure of a sea snake than any fish he had ever seen.
Both Lure Fjord and Lindåsosane to the inside give good living conditions for rare marine organisms: jellyfish, shellfish and fish. These include animals that migrated in after last the Ice Age, when the sea level was higher. Eventually, as the land rose, some of these populations became isolated.
There is a lot of trout and a large char population in Lake Rylandsvatnet. The lake was stocked with char, probably in 1907. The promoters of the project were the family Ameln, who owned eight mills in Rylandsvågen and parts of the Ryland farm.
It is said that the salmon populations with the largest and the smallest salmon in the world both come from the waters that run out into the fjord system around Osterøy. Vosso is supposed to have the largest spawning salmon to be found in any river, whereas Lonelva is said to have the smallest.