New Zealand's forests are comprised mostly of several different species of southern beech trees. Their nuts or seeds drop every few years and cause cyclical booms in the local mouse populations. The trout benefit from these mouse explosions by becoming correspondingly HUGE.
The summer of 2014/2015 (our winter in the Northern Hemisphere) has been a "mouse year" and already I'm hearing many reports of incredible, huge New Zealand brown trout — particularly from the South Island.
This 16-pound brown was caught by artist and FLY FISHERMAN contributor Martin Simpson (martinsimpsonartist.com) this past weekend on a mouse fly he made himself. He actually carved the body portion of the mouse himself out of wood, and glued fur onto the body. It's an incredible fish to come from the small mountain headwater streams where beech trees thrive.