BTRG had a lucky day: two papers were published on the same day.
A short paper about brown trout was published in Croatian journal. Unlike most of our research on brown trout, this paper is not about wild population. We genotyped fish from Fishing Club Bled fish farm to estimate the level of introgression of non native (Atlantic) genetic markers into native (Danubian) brown trout. Introgression was higher in females, probably because survival rate of males in captivity is lower therefore new males are routinely transferred from the wild where introgression is lower.
The second paper is about huchen, an endangered salmonid that matures at 65-70 cm of length and is endemic to the Danube basin. Unlike the highly diverse brown trout, huchen has low genetic variability so even fish from distant locations are genetically very similar. Based on observed markers, samples from 6 countries can be placed into two clusters: Austria / Slovenia and Ukraine / Slovakia / Montenegro / Bosnia-Herzegovina.
There are several possible explanations for low diversity within the species: (1) a slow molecular clock - essentially slow evolution; (2) low historical effective population sizes - small number of "breeders" in the entire basin; (3) a speciation founder effect - all living huchens are descendants of a very small number of ancestral huchens; (4) more recent human-caused bottlenecks - caused by overfishing and habitat degradation.
