This paper is the outcome of the Master thesis of MSc Mari Hagenlund that Kjartan Østbye and I supervised. Mari tested the hypothesis that the recent occurrence of Smelt (Osmerus eperlanus) in lake Storsjøen (Norway) is a result of intentional stocking. It is though that smelt have been stocked in the lake to increase the growth of brown trout (Salmo trutta), an important recreational fish species. Such stocking is illegal in Norway and we and others have previously shown how an invader within only one or two decades may destabilize an entire ecosystem and cause e.g. speciation reversal (See Bhat et al. 2014).
Comparing genetic variation (microsatellites) from smelt samples collected from all the possible post-glacial invasion routes (natural colonization) and samples collected in neighbor lakes (intentional stockings), the paper concludes that the smelt in lake Storsjøen most likely is a result of introduction from the large Lake Mjøsa, and that a significant number (>100) of individuals may have been stocked. We did not identify any effects of bottlenecking in the lake Storsjøen population, but identified indications of a recent population expansion. This indicates that the smelt has been a successful invader.
This paper provides important information for nature managers in how to handle future reports on intentional stockings and allow for planning of strategies of prosecution in cases of fauna crime. It also illustrates the power of genetic tools in nature management.
All laboratory analyses and subsequent genotyping were performed at the genetic lab at UiT.