In 1867, New Zealand introduced brown trout for sport fishing; more than 60 million were released

In 1867, British settlers introduced brown trout to New Zealand, intending to enhance sport fishing.

This decision led to the release of over sixty million trout, which had devastating effects on local fish populations, resulting in declines and even extinction of some native species.

The presence of these invasive fish fundamentally changed stream ecosystems and insect behaviors, making their management a significant conservation challenge even today.