Conservation of Marble Trout in the upper basin of the Soča (Slovenia)


Juvenile marble trout (Salmo marmoratus) © Florian Leborne / Tour du Valat © F.Le Borne


This project was initiated in 1993 when the Slovenian researcher Meta Povz alerted Alain Crivelli at the Tour du Valat about the imminent extinction of the Marble Trout (Salmo marmoratus) in the Soča basin, in Slovenia. At that time, the Marble Trout, an endemic species of the Adriatic basin, was threatened by the massive introduction of Brown Trout (Salmo trutta) with which it could hybridize. In 1996, a conservation plan was set up by the Tour du Valat to save the Marble Trout and preserve its upstream habitats, which were still almost untouched by human activities. The monitoring conducted with the Tolmin fishing association since 1996, has enabled us to better understand the population dynamics of this species vis-à-vis two species of exotic trout, the Brown Trout and the Rainbow Trout (Oncorhynchus mykiss), and extreme events such as floods, landslides, and periods of drought.

Actions and methodology

  • 1993 – 1996: Eight populations of genetically pure Marble Trout were identified at the head of the basin. They had been naturally isolated by waterfalls that were impassable for the hybrid trout downstream.
  • 1996: the conservation plan was launched, and the duplication of the genetically pure Marble Trout was started. The first two new populations were created, and the first capture-mark-recapture (CMR) monitoring programme was set up.
  • Since the 2000s, more than 20 populations have been monitored in line with specific objectives. Today, 17 sites are being monitored annually or bi-annually.
  • 1999 – 2014: An in-situ study was conducted on the hybridization of the Brown Trout and the Marble Trout at three sites.
  • 2004 – today: One population of naturalised Brown Trout has been monitored (CMR) to characterise its life traits and population dynamics at one site.
  • 2008 – today: All genetically pure populations have been monitored (CMR), particularly their population dynamics, morphological and genetic variations, and family ties between successive generations to better understand the processes of adapting to flood-related phenomena (nine sites).
  • 2008 – today: Populations of Rainbow Trout have been monitored that are naturalised or sympatric (with Marble Trout or hybrids), in order to characterise their ecology and study the competition between the different species (five sites).
  • 2008 – today: The recolonization dynamics of the Rainbow Trout has been studied following a landslide in 2011 (three sites).
  • 2013 – 2017: The diet of allopatric and sympatric Marble Trout was studied with an estimation of cannibalism (eight sites).


  • Project leader: Delphine Nicolas
  • Date of project: since 1993

Technical partners


  • Berrebi, P., Jesenšek, D. and Crivelli, A.J. (2016) Natural and domestic introgressions in the marble trout population of Soča River (Slovenia). Hydrobiologia.
  • Berrebi, P., Povz, M., Jesensek, D., Cattaneo-Berrebi, G. and Crivelli, A. (2000) The genetic diversity of native, stocked and hybrid populations of marble trout in the Soca River, Slovenia. Heredity 85 Pt 3, 277–87.
  • Crivelli, A. J., Poizat, G., Berrebi, P., Jesensek, D. and Rubin, Jean-François (2000) Conservation biology applied to fish: The example of a project for rehabilitating the marble trout (Salmo marmoratus) in Slovenia. Cybium 24, 211–230.
  • Musseau, C., Vincenzi, S., Jesenšek, D., Cantera, I., Boulêtreau, S., Santoul, F. and Crivelli, A.J. (2015) Direct and indirect effects of environmental factors on dietary niches in size-structured populations of a wild salmonid. Ecosphere 6, 1–15.
  • Pujolar, J.M., Vincenzi, S., Zane, L. and Crivelli, A.J. (2016) Temporal changes in allele frequencies in a small marble trout Salmo marmoratus population threatened by extreme flood events: temporal genetic changes in salmo marmoratus. Journal of Fish Biology, n/a-n/a.
  • Pujolar, J.M., Vincenzi, S., Zane, L., Jesensek, D., De Leo, G.A. and Crivelli, A.J. (2011b) The Effect of Recurrent Floods on Genetic Composition of Marble Trout Populations. Plos One 6.
  • Stanković, D., Crivelli, A.J. and Snoj, A. (2015) Rainbow Trout in Europe: Introduction, Naturalization, and Impacts. Reviews in Fisheries Science & Aquaculture 23, 39–71.
  • Vincenzi, S., Crivelli, A.J., Giske, J., Satterthwaite, W.H. and Mangel, M. (2012a) Selective consequences of catastrophes for growth rates in a stream-dwelling salmonid. Oecologia 168, 393–404.
  • Vincenzi, S., Crivelli, A.J., Jesensek, D. and De Leo, G.A. (2010a) Detection of density-dependent growth at two spatial scales in marble trout (Salmo marmoratus) populations: Density-dependent growth at two spatial scales. Ecology of Freshwater Fish 19, 338–347.
  • Vincenzi, S., Crivelli, A.J., Jesensek, D. and De Leo, G.A. (2010b) Individual growth and its implications for the recruitment dynamics of stream-dwelling marble trout (Salmo marmoratus): Individual growth and recruitment dynamics of marble trout. Ecology of Freshwater Fish 19, 477–486.
  • Vincenzi, S., Crivelli, A.J., Jesenšek, D. and De Leo, G.A. (2010c) The management of small, isolated salmonid populations: do we have to fix it if it ain’t broken? Animal Conservation 13, 21–23.
  • Vincenzi, S., Crivelli, A.J., Jesensek, D. and De Leo, G.A. (2008a) The role of density-dependent individual growth in the persistence of freshwater salmonid populations. Oecologia 156, 523–534.
  • Vincenzi, S., Crivelli, A.J., Jesensek, D. and De Leo, G.A. (2008b) Total population density during the first year of life as a major determinant of lifetime body-length trajectory in marble trout. Ecology of Freshwater Fish 17, 515–519.
  • Vincenzi, S., Crivelli, A.J., Jesensek, D. and De Leo, G.A. (2012b) Translocation of stream-dwelling salmonids in headwaters: insights from a 15-year reintroduction experience. Reviews in Fish Biology and Fisheries 22, 437–455.
  • Vincenzi, S., Crivelli, A.J., Jesensek, D., Rossi, G. and De Leo, G.A. (2011) Innocent until proven guilty? Stable coexistence of alien rainbow trout and native marble trout in a Slovenian stream. Naturwissenschaften 98, 57–66.
  • Vincenzi, S., Crivellì, A.J., Jesensek, D., Rubin, J.-F. and De Leo, G.A. (2007a) Density-dependent individual growth of marble trout (Salmo marmoratus) in the Soca and Idrijca river basins, Slovenia. Hydrobiologia 583, 57–68.
  • Vincenzi, S., Crivellì, A.J., Jesensek, D., Rubin, J.-F. and De Leo, G.A. (2007b) Early survival of marble trout Salmo marmoratus: evidence for density dependence? Ecology of Freshwater Fish 16, 116–123.
  • Vincenzi, S., Crivelli, A.J., Jesensek, D., Rubin, J.-F., Poizat, G. and De leo, G.A. (2008c) Potential factors controlling the population viability of newly introduced endangered marble trout populations. Biological Conservation 141, 198–210.
  • Vincenzi, S., Crivelli, A.J., Munch, S., Skaug, H.J. and Mangel, M. (2016a) Trade-offs between accuracy and interpretability in von Bertalanffy random-effects models of growth. Ecological Applications.
  • Vincenzi, S., Crivelli, A.J., Satterthwaite, W.H. and Mangel, M. (2014a) Eco-evolutionary dynamics induced by massive mortality events: eco-evolution and resilience. Journal of Fish Biology 85, 8–30.
  • Vincenzi, S., De Leo, G.A. and Bellingeri, M. (2012c) Consequences of extreme events on population persistence and evolution of a quantitative trait. Ecological Informatics 8, 20–28.
  • Vincenzi, S., Jesensek, D. and Crivelli, A.J. (2015) Vital rates, source-sink dynamics, and type of competition in congeneric species. biorxiv;033720v1.
  • Vincenzi, S., Mangel, M., Crivelli, A., Munch, S. and Skaug, H. (2014b) Determining individual variation in growth and its implication for life-history and population processes using the empirical bayes method. PLoS computational biology 10, e1003828.
  • Vincenzi, S., Mangel, M., Jesensˇek, D., Garza, J.C. and Crivelli, A.J. (2016b) Within- and among-population variation in vital rates and population dynamics in a variable environment. Ecological Applications 26, 2086–2102.
  • Vincenzi, S., Mangel, M., Jesensek, D., Garza, J.C. and Crivelli, A.J. (2017) Genetic and life-history consequences of extreme climate events. Proceedings. Biological Sciences 284.