Untitled

Abstract

Brown trout Salmo trutta wild stocks sustain a remarkable angling and hatchery-reared fish stocking pressure in waters of Serbia, where four drainage-specific and indigenous mitochondrial DNA haplotypes were reported for the drainage area of the Danube River basin. One of these mitochondrial DNA haplotypes, Da23b, was exclusive for brown trout in headwaters of the Crni Timok River (Grand Timok River system, Eastern Serbia). After its discovery in 2003, brown trout stocking was completely halted and abandoned, and a strict Catch-and-Release fishing regime was issued. However, failure of this regime due to enforcement resulted in decline of brown trout fishery. On checking the aboriginality of brood fish sampled in three headwater forks for artificial brown trout propagation, a novel, drainage-specific mtDNA haplotype was recorded in 54% of brown trout. It was assigned Da23c, due to its similarity (substitutions at the two variable sites) to the hitherto known haplotypes of Da23 group. Its finding and absence of Da23b haplotype imply an oversight in earlier haplotype determination. Incorporation of the non-indigenous haplotypes Da2 and Da-s1, introduced in the area by stocking before 2003, into the gene pool of native brown trout and declining of the latter's stock imposes the need for the more stringently enforced conservational activities (genotyping of each brood fish involved in artificial propagation) and improved fisheries management (Catch-and-Release) in the area.

Risks to stocks of native trout of the genus Salmo (Actinopterygii: Salmoniformes: Salmonidae) of Serbia and management for their recovery

“…Species native to and introduced from streams of the Balkans area (e.g., of Da1, Da2, and Da22 haplotypes of brown trout; Adcs11 and Ad-Prz of Adriatic trout; Adcs1Macedonian trout; and Ohrid trout of unknown haplotype) were regarded as translocated. The proportion of trout holding alien haplotypes for each stream (Table 1) was calculated from records of genotyping (Marić et al 2006a, Tošić et al 2014 and from records for the Jerma River as provided in the presently reported study. Eleven trout individuals from the Jerma River sampled in 2013 by fl y fi shing were additionally analysed for their mtDNA haplotype using the methodology for DNA extraction and D-loop amplifi cation described in Tošić et al (2014).…”

“…Brown trout in streams of Serbia were found to belong to three of those lineages: Da, Ad, and At, each having several variants (haplotypes). In addition to the widespread native (Da1, Adcs1, and Adcs11) and introduced (Da2, Atcs1) mtDNA haplotypes, several new, native haplotypes were discovered in all three drainage areas of Southern Serbia (Marić et al 2006a, Tošić et al 2014. Some of them (Da-Vr, Da-Dž, and Ad-Bož) were found to be intermediate between the Danubian (Da) and Adriatic (Ad) lineages (after Bernatchez et al 1992).…”

“…Likewise, the tentatively vicariant Da-s6 (Genbank accession code U18202) and Da22 haplotypes, which were so far known only from the Caspian Sea drainage area of Iran (Bernatchez 2001) and upper Danube River basin in Austria (Duftner et al 2003), respectively, were reported for the Studenačka and Rosomačka rivers in south-eastern Serbia. Finally, the last discovered native mtDNA haplotype of wild brown trout was Da23c, which Tošić et al (2014) reported as exclusive for eastern Serbia.…”

“…Likewise, the tentatively vicariant Da-s6 (Genbank accession code U18202) and Da22 haplotypes, which were so far known only from the Caspian Sea drainage area of Iran (Bernatchez 2001) and upper Danube River basin in Austria (Duftner et al 2003), respectively, were reported for the Studenačka and Rosomačka rivers in south-eastern Serbia. Finally, the last discovered native mtDNA haplotype of wild brown trout was Da23c, which Tošić et al (2014) reported as exclusive for eastern Serbia.The exclusive occurrence of trout species of non-indigenous haplotypes in specifi c streams out of their native dispersal area (e.g., Adriatic trout, Salmo farioides Karaman, 1938, of the Ad-Prz mtDNA haplotype in the Tripušnica River, Vardar drainage area; Macedonian trout of the Adcs1 haplotype in the Jerma River, Velika Morava drainage area) (Table 1), points to the occurrence of stocking events into either hitherto pristine streams (i.e., free of wild brown trout), or streams holding wild brown trout of the Danubian lineage, respectively. Also, Macedonian trout was reportedly stocked into the Jerma River about 15 years ago (Marić et al 2006a), Lake Ohrid trout, Salmo letnica (Karaman, 1924), was heavily and repeatedly stocked from a hatchery into the Vlasina Lake in Southern Serbia in 1950s and 1960s for commercial fi shing purposes (Janković and Raspopović 1960).…”

“…The proportion of trout holding alien haplotypes for each stream (Table 1) was calculated from records of genotyping (Marić et al 2006a, Tošić et al 2014 and from records for the Jerma River as provided in the presently reported study. Eleven trout individuals from the Jerma River sampled in 2013 by fl y fi shing were additionally analysed for their mtDNA haplotype using the methodology for DNA extraction and D-loop amplifi cation described in Tošić et al (2014). The amplifi ed D-loop region of the mtDNA was analysed using AluI and SatI endonucleases.…”