9781934874547-ch13

Trout and Char of the World

13: Trout of Southeast Europe, Western and Central Asia

Johannes Schöffmann, Saša Marić, and Aleš Snoj

doi: https://doi.org/10.47886/9781934874547.ch13

The natural range of trout belonging to the genus Salmo extends all over Europe and northwest Africa, from Anatolia to the Caucasian region and northern Iran up to central Asia near the border of China. Due to this vast distribution area with highly varying environmental conditions, a large number of different ecological and morphological forms of trout, often described as separate species or subspecies, have evolved since the split from a common ancestor of the Atlantic Salmon Salmo salar and the lineage that led to the present trout species (Salmo spp.) roughly 5 million years ago (MYA; Pustovrh et al. 2014). Moreover, climatic fluctuations during the Pleistocene, starting about 2.6 MYA affected the habitats and the geographic range of trout. In warmer interglacial periods, trout were able to spread over the northern parts of Europe covered with ice during glacial periods while they survived the cold periods in southern retreat areas. On the other hand, higher interglacial temperatures in these southern refugia caused trout to retreat to the source reaches, mostly situated in high altitudes. As a result of these periodically changing conditions, trout populations repeatedly became fragmented and underwent independent evolutionary developments, leading to the enormous genetic diversity known today. Based on mitochondrial DNA (mtDNA), five major evolutionary lineages are generally accepted so far (Bernatchez 2001). The Atlantic lineage occurs in the entire Atlantic basin of Europe, including the uppermost drainages of Europe’s longest rivers, the Volga (Osinov and Bernatchez 1996) and Danube (Lerceteau-Köhler et al. 2013), which flow into the Caspian Sea and Black Sea, respectively. A closely related lineage from the drainage area of the Duero River in Spain has been suggested (Suárez et al. 2001). In Morocco, both the Atlantic and the Mediterranean basins are populated by the Atlantic lineage (Bernatchez 2001; Snoj et al. 2011). During the last ice age, Atlantic trout may have dispersed along the north coast of Africa eastward as far as Sicily (Schöffmann et al. 2007). There are three distinct lineages with partially overlapping distribution in the northern Mediterranean basin: the Adriatic lineage from the southern and eastern Iberian Peninsula in the west to southern Turkey in the east, including the Euphrates drainage (Bernatchez 2001); the Mediterranean lineage in the western Mediterranean basin from northeast Spain to the southwest Balkan Peninsula; and the marmoratus lineage, primarily distributed in the northern Adriatic basin. The vast remaining territory is occupied by the Danubian lineage in the basins of the Black Sea, Caspian Sea, and Aral Sea, as well as in the uppermost Euphrates River drainage and the Tigris River drainage of eastern Turkey and even in some Mediterranean tributaries of northwest Turkey (Bernatchez 2001; Sušnik et al. 2005). Two additional, more ancient, and well-defined lineages are known from the Balkans: Softmouth Trout Salmo obtusirostris and S. ohridanus, known locally as belvica (Snoj et al. 2002; Sušnik et al. 2007a).