Haplotype diversity of brown trout Salmo trutta (L.) in the broader Iron Gate area

Abstract

Mitochondrial DNA (mtDNA) haplotypes of brown trout (Salmo trutta L.) populations in the area of Djerdap National Park were analyzed in order to determine their phylogeographic statuses. Sequencing the control region of mtDNA in 66 specimens from 9 streams in the broader Iron Gate area revealed that 7 brown trout from those streams carried haplotypes of Atlantic lineage, while the remaining 59 fish were of Danubian lineage, either of Da23c or Da1 haplotypes. Four streams were inhabited by populations of the indigenous Da23c mtDNA haplotype, while the population in one stream had the Da1 haplotype. In the remaining 4 streams, brown trout of exclusively Atlantic lineage were present in 3, while those of the Da23c haplotype were additionally present in the fourth. The significant fixation index Fst in all populations, caused by a significantly large proportion of the among-population component of variance, revealed the fixation of particular haplotypes in the majority of populations. The size of a particular stream determines native brown trout abundance and limits their suitability for restorative purposes.

Alternative Life-History in Native Trout (Salmo spp.) Suppresses the Invasive Effect of Alien Trout Strains Introduced Into Streams in the Western Part of the Balkans

“…In contrast to the positive effects that sustainable management in trout fisheries have [e.g., the conditional and unconditional catch-and-release (Simonović et al, 2018)], both fishery managers and trout farmers fostered stocking of farmed brown trout fry and even spent brood fish (Simonović et al, 2014) to quickly enhance brown trout fisheries and accelerate return of investments (Simonović et al, 2017b). Based on recent knowledge of the native diversity of brown trout in the Western Balkans (Marić et al, 2006;Simonović et al, 2017a) and the risks posed to them by the introduction of non-native strains of brown trout and related species might pose to them (Simonović et al, 2013(Simonović et al, , 2015, recent surveys have revealed the occurrence of permanent, long-lasting introduction caused by stocking streams attractive for trout fisheries (Simonović et al, 2014;Škraba Jurlina et al, 2018), streams originally devoid of trout prior to stocking (Jadan et al, 2007;Simonović et al, 2018), and even streams that are not at all suitable for brown trout fisheries (Tošić et al, 2016;Škraba et al, 2017). Introduction of trout fish of the non-native haplogroups and of the non-native haplotypes in the dispersal area of brown trout of the DA haplogroup in the Western Balkans has been a long-standing practice since the mid-nineteenth century at least, when Slovenia, Croatia, and Bosnia and Herzegovina were parts of the Austro-Hungarian Empire (Razpet et al, 2007;Simonović et al, 2017b).…”

“…In the inland waters of the Danube River catchment, reservoir-dwelling migrating trout were recorded soon after the construction of dams, though it is not yet known whether those individuals belong to native trout of the DA lineage or to introduced trout of the AT lineage or whether they are an admixture of both of them. The discovery of brown trout individuals in the Djerdap (Iron Gate) One reservoir and in the lowermost sections of streams draining into the Danube River there (Figure 1, localities 1-7) confirmed they belong to the AT lineage or are admixed with it (Marić et al, 2012;Simonović et al, 2015Simonović et al, , 2017aTošić et al, 2016). There are no records of these trout in the upstream, headwater sections, where pure brown trout of the very specific Da23c haplotype still occur (Tošić et al, 2016).…”

“…Fin clips were collected from 10 individuals from the Svetinja River, from 11 caught in the Krušnica River, from 11 individuals caught in the lower reach, and 12 from the upper reach of the Mrtvica River, where the size of samples was limited most likely by extensive poaching occurring there (Škraba Jurlina et al, 2018). As for the Danube River tributaries in the Iron Gate Gorge area, fin clips were collected from each of a very small number of individuals due to their small size and the scarcity of water and brown trout in those streams (Tošić et al, 2016), [e.g., two samples from the Brnjica River, 18 from the KoŽica River, six from the Mala Boljetinska River, 12 from the Zlatica River, 11 from the north fork of the Rečka River, 10 from the Vratna River, and seven from the Zamna River (Figure 1, localities 7, 4, 5, 6, 3, 2, and 1, respectively) ( Supplementary Table)].…”

“…In all streams in the Iron Gate Gorge area, brown trout of the AT haplogroup were recorded in the Brnjica River, Dobra River, and Porečka River and in the Danube River near the confluence with the Dobra River, while in the Vratna River, they were found in sympatry with the brown trout of the Da23c haplotype (#KC630984; Tošić et al, 2014), [i.e., three of 10 (33%) brown trout in total were of this haplotype (Tošić et al, 2016)].…”

“…presented here was recently supplemented with a prominent insight into their diversity, assessed using molecular markers, both mitochondrial, [e.g., cytochrome b and control region (CR), i.e., the D-loop (Bernatchez et al, 1992;Bernatchez, 2001), and nuclear, e.g., LDH-C * and several microsatellite loci (Hamilton et al, 1989;Richard and Thorpe, 2001)]. The basic mapping of indigenous populations of nominal trout taxa accomplished using CR as a marker in the Adriatic Sea Basin assigned them to the Adriatic (AD), marmoratus (MA), and Danubian (DA) mtDNA lineages (Marić et al, 2006;Mrdak, 2011;Mrdak et al, 2012;Simonović et al, 2017b;Škraba Jurlina et al, 2018); those native to the Black Sea Basin belonged to the DA lineage (Marić et al, 2006;Mrdak, 2011;Tošić et al, 2014Tošić et al, , 2016Simonović et al, 2017b;Škraba et al, 2017), whereas in the Aegean Sea Basin, they belonged to the AD lineage (Marić et al, 2006(Marić et al, , 2017LoBrutto et al, 2010).…”