Party

BTRG celebrated the 2000th visitor of our website in a Bosnian restaurant. Special guest star was of course David, the designer of www.balkan-trout.com. Frequent site visitors already know his lovely wife Tamara.

Marble trout

A new fish taxon was added to the balkan-trout site.

Marble trout (Salmo marmoratus) is native to the North Adriatic river systems (e.g. the Po river system in Italy and the Soča/Isonzo river system in Slovenia and Italy) and is one of the most endangered freshwater species. The main threat has been hybridization with introduced brown trout. Dr. Meta Povž from Fisheries Research Institute of Slovenia, French researchers Dr. Alain Crivelli and Dr. Patrick Berrebi and Dušan Jesenšek, the manager of Tolmin fish farm of the Angling Club of Tolmin are just a few of people involved in an action plan for marble trout restoration, which was initiated in 1992 and later joint also by the Department of Animal Science at the University of Ljubljana.

Read more about it in Studied taxa.

Website report for 2007

The traffic on our website is monitored by StatCounter and Google. Both have several limitations, but we can get a decent picture of what our visitors are looking for and where they came from. Most of the last 500 visitors (68.71%) were not from Slovenia, which is one of the reasons why the site currently exists in English version only. Last 500 visitors were from:

31.29% Slovenia
11.06% United States
7.29% Serbia And Montenegro
6.82% Italy
5.18% Austria
4.47% Croatia
4.00% Bosnia And Herzegovina
4.00% Sweden
3.76% Russian Federation
3.53% United Kingdom
2.35% Japan
1.88% Bermuda
1.65% Czech Republic
1.65% France
1.41% Denmark

One of the limitations is the inability of StatCounter to distinguish properly visitors from Serbia and from Montenegro, sometimes placing them in "unknown" or third countries. A lot of visitors came from internet forums, Patagonia websites and from Google search results. Google search queries that returned pages from our site and were clicked in the last 3 months of 2007 were:

26% balkan trout
7% softmouth trout in croatia
6% potočna pastrmka rijeke bune
4% atlantski losos
4% lososu podobna sladkovodna riba
4% sasa maric
4% world distribution of brown trout
3% biolog sasa maric
3% radovanjska reka
2% balkan razpet
2% golema reka pastrmka
2% neretva
2% rečna pastrmka
2% salmo trutta marmoratus
2% soft mouth trout
2% softmouth trout
2% zubatak
2% berrebi patrick
2% egejski recen sliv na makedonija
2% geneticka varijabilnost prirodnih populacija metode procene
2% geologija cetina
2% koje reke pripadaju jadranskom slivu
2% mesinska kriza saliniteta
2% ogrožena soška postrv
2% recni pritoki vo makedonija
2% sadasnji i perspective vidovi koriscenja reke u pirotu
2% salmo marmoratus
2% steven weiss slovenia
2% zubatak iz krke

One of the reasons why our site was named Balkan Trout is that it is easy to remember.

Native and genetically pure brown trout of the Danubian drainage

A paper by Andrej & Aleš was published in "Ribič", Journal of the Association of Slovenian Fishermen (not the official English name of the organization).

This paper was a response to several papers in the Ribič journal where genetically pure and /or native brown trout were mentioned. Problematics of hybridization with non native brown trout was presented as well as published and unpublished results of our surveys in several Slovenian rivers.

It is worth to mention that Kottelat and Freyhof in their "Handbook of European Freshwater Fishes" (2007) use the almost forgotten name Salmo labrax for native brown trout of the Danubian drainage.

A new piece of equipment

Annual testing of marble trout from zone of hybridization

One of the success stories of fish restoration comes from the west part of Slovenia (the River Soča and its tributaries). Native marble trout was under threat because of hybridization with non-native brown trout that was being stocked in the rivers for decades. In the 90s, the last 8 populations of genetically pure marble trout were identified and used in marble trout restoration program. The native range of marble trout is mostly stocked with offspring of fish from these 8 populations. However, these populations have low genetic variability, therefore individuals from the zone of hybridization are also used in the restoration program so that genetic diversity of marble trout from the zone of hybridization is not lost. The problem is how to select individuals from zone of hybridization that don't have (too much) non native genetic characteristics.

We performed genetic testing of fish from the zone of hybridization for the last 5 years. This year we have received fin clips from 34 individually tagged trout from the River Tolminka, tributary of the River Soča. These samples were checked for non native genetic characteristic on 6 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 34 samples, 14 show signs of hybridization with non native trout. Eggs and sperm will be taken from 20 trout with no detectable brown trout genetic characteristics, fertilised and raised in the hatchery and released back in the zone of hybridization.

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 taken from the river, so the actual percentage of non native alleles in Tolminka might differ from our results (6%).

Table of genotypes across 1 mitochondrial and 6 nuclear markers. Samples with non native (=brown trout alleles) are marked red and will not be used in restoration program. f - female, m - male, M - marble trout specific allele, B - brown trout specific allele.

Tissue samples

A new set of photos was added to the site to show the appearance of tissue samples as they arrive in our laboratory. Nowadays we mostly work with fin clips, taking blood and scales during field trips seems to be less practical, even tough it is possible to isolate DNA from just about any material.