The Ice Age Brown Trout

If you have looked into fishing in Iceland you have probably heard the term "ice age brown trout" and seen people rave about their size and strength. But what exactly is an ice age brown trout, how do they differ from a regular brown trout and why are they so highly praised and sought after?

The short answer; ice age browns is the name given to the strain of brown trout inhabiting Lake Þingvallavatn, Iceland's largest natural lake. The reason people get obsessed with these beasts is quite frankly their incredible size, as well as fighting strength, not to mention the beauty of this creature. Fish over 30 lbs are caught each year.

For the long answer, we need to go back 11 thousand years when the ancestors of the ice age trout moved in from the ocean and colonized the area. Those ancestors were anadromous brown trout that moved back and forth between Lake Þingvallavatn and the open ocean. Roughly 9 thousand years ago reciting glaciers and volcanic activity made passage between Lake Þingvallavatn and the ocean impossible, in effect trapping these previously sea-run fish in the lake. In the time that has passed since then, the trout have made some remarkable adaptations to their new surroundings, one of which is the fact that the ice age trout only reach sexual maturity between the ages of 5-8 years old. In a research done by biologist Jóhannes Sturlaugsson, an ice age brown trout that had reached over 20 lbs in size but was not yet sexually mature, was found. Another remarkable adaptation that the strain shows is the fact that unlike most other brown trout in Iceland, the strain does not spawn every year once reaching sexual maturity, but in fact, each fish only spawns every 2-3 years. Those years that the fish do not expand their energy at spawning they pack on weight and size fast. With remarkable growth rate up to 5 lbs a year has been documented in tagged fish. 

The main food sources for these fish are threefold, the 3-spined stickleback which is a small fish inhabiting the shallows of the lake, any of the 4 sub-species of Arctic char that inhabit the lake but mainly the Murta sub-species (Salvelinus Alpinus Murta) as well as insect life mainly in the form of midges, Chironomidae and caddis in all life cycles. These feeding patterns make them perfect to target with a fly rod as they will take streamers, nymphs and dry flies when presented to them.

The fishing season for them last from 15 April until September, with primetime usually being 15 April-15 June.

For more information on research done on the ice age brown trout, we recommend checking out http://www.laxfiskar.is/index.php?lang=en

By Sindri Hlíðar Jónsson, Partner and Head Guide at Fish Partner