Alaska eliminates invasive pike and restocks lake with 6,836 Arctic char

Alaska biologists treated an entire lake with rotenone to eliminate an invasive northern pike population, then began restoring the native fishery with thousands of Arctic char.

The project focused on Stormy Lake near Anchorage. In fall 2012, the Alaska Department of Fish and Game treated the lake and its outlet creek with liquid rotenone. Follow-up netting and electrofishing surveys found no surviving pike.

In June 2013, the agency stocked 6,836 hatchery-reared Arctic char fingerlings into the pike-free lake. The stocking was intended to restart a native fishery that the predator had displaced.

Northern pike are not native to most of Southcentral Alaska. They were illegally introduced into several lakes in the mid-20th century and spread through connected waterways. The fish prey on native species including salmon, trout, grayling and char, and have severely reduced native sport fish populations in some lakes.

The agency uses rotenone in isolated lakes where complete removal is possible. The plant-derived piscicide blocks oxygen uptake in fish gills, while breaking down relatively quickly in sunlight and warm water. The article says draining a lake or using a piscicide such as rotenone are the only proven methods for eradicating invasive fish from a lake.