Saturday, November 21, 2009

Annual testing of marble trout from zone of hybridization

Just like last year and a year before that, we performed genetic testing of fish from the zone of hybridization. This year we have received fin clips from 43 individually tagged trout from lower Trebuščica (the upper is home to one of 8 genetically pure populations of marble trout). These samples were checked for non native genetic characteristic on 5 nuclear genetic markers (each genetic marker in 2 copies, one allele inherited from each parent) and on 1 mitochondrial genetic marker (in 1 copy, inherited from the mother only). Out of 43 samples, 13 show signs of hybridization with non native trout, 4 sample will not be used because of low quality of DNA isolate (not included in the table). Eggs and sperm will be taken from 26 trout with no detectable brown trout genetic characteristics, fertilised and raised in the hatchery, released back in the zone of hybridization. DNA isolation and genotyping was carried out by Gašper.

Below is a simplified table of genotypes. These genotypes are not publishable, since the initial sampling was biased, only marble trout (by general appearance) were sampled, so the actual percentage of non native alleles in sampled locations might differ from our results (8.2% for nuclear markers, 2.6% for mtDNA marker).

Table of genotypes across 1 mitochondrial and 5 nuclear markers. Samples with non native (=brown trout alleles) are marked red and will not be used in restoration program. M - marble trout specific allele, B - brown trout specific allele.


  1. Is there any information on what will happen with the confirmed hybrid individuals?

  2. I forwarded the question to Tolmin Anglers, waiting for reply.