THE MARBLE TROUT

 Jurij POHAR

 The Marble trout (salmo trutta marmoratatus) is an endemic type of trout in the waters   of the Adriatic river basin.  To the river Soca, the brown trout (Salmo trutta )was introduced at the beginning of this century. Since the marble trout and brown trout can cross-breed, the marble trout has become an endangered species.
The basic color of the trout is olive brown and olive green.  Characteristically it has a yellowish-green marbling usually  found on the side of the body.  Compared to the brown trout it has a relatively large head.
The National Institute for Fisheries and The Sport Fishing Association of Tolmin started a project which was aimed to prevent the extinction of this type of trout.
It has been speculated that in some tributaries it is still possible to find  populations of marble trout which are genetically pure. Records have shown that brown trout was not introduced there by the means of  repopulation and at the same time these tributaries are separated from the main river by barriers which prevent immigration  of the brown trout from the main river course.
To prevent the extinction of marble trout, no non-autochtonous trout will be allowed to be introduced into the Soca river and its tributaries. At the same time only fry and fingerling which are offsprings of the genetically pure broodstock should be used to repopulate the Soca river. Therefore the sufficient number of fry and fingerling of  genetically pure marble trout will be grown each year on fish farms.
To make this possible a method to differentiate between  the genetically pure Marble trout and the cross-breed trout is needed. At the Zootechnical Department of the Biotechnical Faculty (University of Ljubljana) several research projects have been conducted with the  goal to find appropriate genetic markers that would allow fast, reliable and simple differentiation of the Marble trout from the cross-bred trout.

References:
1 .Jesenšek, D.: Soška postrv: njene značilnosti in značilnosti njenih križancev, Ribičeva knjižica, 1998, 72s.
2. Pohar, J. in K. Al-Sabti: Kromosomska slika marmorirane postrvi in lipana. Zbornik Biotehniške fakultete, Kmetijstvo (živinoreja), 32:77-96
3. Povž, M., D. Jesenšek, P. Berrebe in A. J. Crivelli: Soška postrv (Salmo trutta marmoratus, Cuvier 1817) v porečju Soče v Sloveniji. Tour de Valat, 1996. 65 s.
4. SNOJ, A., POHAR, J., DOVČ, P.: Rapid Communication: The First Microsatelite DNA Marker for Marble Trout, BFRO 001, J. Anim. Sci., 1997, 75, s. 1983
6. SNOJ, A.: Molekularno biološka karakterizacija soške postrvi (Salmo marmoratus, Cuvier 1817): doktorska disertacija = Molecular biologic characterization of marble trout (Salmo marmoratus, Cuvier 1817): dissertation thesis. Domžale: [A. Snoj], 1997. X, 111 f., ilustr.

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