There is a Lough half way up a mountain where my brother and I spend a day or two each year. It’s not easy to reach. The climb, over the sodden ground, saps the energy from our legs and makes us pause every now and then to catch our breath. During these short breaks we turn our backs on the mountain, and face instead, the open country beneath us. There is plenty to see. The flat green country is partitioned by the upper river Shannon. There are loughs everywhere. Some of the larger ones we can name, but he small ones are beyond counting; each one a jewel nestled into a fold in the velvet landscape. And all around us the air carries the sound of the tiny rivulets which gather the water from mountain and begin to steer it, well beyond our vision, towards the ocean.

My brother Sean discovered this Lough about eleven years ago. It wasn’t easy to find. It seems unusual to locate a lough by climbing upward and, in many ways, he was lucky to find it at all. It is very small, and it is quite invisible until you arrive at a ridge and discover it, quite suddenly, at your feet. And sometimes it is not there at all. The dark clouds that graze the mountaintops here may throw a protective blanket around it, and steal it back. On such days we are forced to turn away and leave the fish to cruise the peaty waters undisturbed.

The brown trout here rise freely, as though to reward the fisherman for the effort he made to reach them. They are not big fish: the heaviest we have taken is probably little more than a pound. They will readily accept a simple wet fly though, preferably one which is black and sparsely tied. And they look up too, and are happy to intercept the dry fly we prefer to offer them.

Sean and I took my son Leo here to catch his first trout on the fly. We were on a short fishing trip and would soon be heading towards Lough Cara to fish teams of wets from a drifting boat. The fishing there can be tiring and, when the thoughts of the trout are elsewhere, it can be slow. For this reason we decided to head first to the Mountain Lough whose eager fish might offer Leo the greatest prospect of early success. And sure enough, within ten minutes or so of our arrival, a swirl distorted the mirror of the surface, and his deer hair sedge was gone. A few moments later, we were admiring the varnished flank of Leo’s first trout before he gently lowered his hand from its belly and let the black water reclaim it.

The brown trout of the Mountain Lough are enigmatic creatures. We have caught a good number over the years and they have a very uniform appearance. They have black backs and copper flanks and, beneath the dark rows of spots on the dorsal surface, two rows of red spots, each nested in a pale halo. It seems to me that their strict conformity to dress code might say something about their history. This Lough is isolated and fed only by a stream which gathers rainfall from the mountain ridge above. How did the trout get here? In my imagination at least, this is the relic of a population which colonised the waters in deep time: descendants of ancestors who staked their claim to this water through conduits long since vanished in a landscape of ice and glaciers and a wilderness unseen by human eyes. Perhaps this is so. Certainly, as the scientists point out, reduced physical and genetic diversity might be expected in a small population long isolated from others.

To commemorate Leo’s first trout, I painted it in watercolours. It is framed now and hangs on his bedroom wall. It is not a good painting, though. While its proportions are approximately correct and its colours passably resemble the original, I could no more capture its beauty using pigments than I now can, using words. If you wish to see for yourself how beautiful these trout really are you must go there. Clear your diary for a day. Put on your walking boots, take a light fly rod and a box of simple flies, and pray that, for a few hours at least, the possessive clouds will surrender the Mountain Lough to you.

Published as “A Breed Apart” by Fly Fishing and Fly Tying Monthly, February 2013