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

Abstract

Simonović P., Vidović Z., Tošić A., Škraba D., Čanak-Atlagić J., Nikolić V. 2015. Risks to stocks of native trout of the genus Salmo (Actinopterygii: Salmoniformes: Salmonidae) of Serbia and management for their recovery. Acta Ichthyol. Piscat. 45 (2): 161-173.Background. Insuffi ciently controlled stocking compromises the high diversity of wild trout stocks of Serbia. Native brown trout, Salmo cf. trutta Linnaeus, 1758, and Macedonian trout, Salmo macedonicus (Karaman, 1924), reveal remarkable diversity assessed using the mtDNA molecular markers, with the eight exclusive and several more widely spread haplotypes found in them. Four alien trout species and strains and one strain of Macedonian trout were introduced into the home areas of the native wild trout stocks in Serbia. In addition to them, wild trout stocks were also affected by farmed rainbow trout, Oncorhynchus mykiss (Walbaum, 1792), and brook trout Salvelinus fontinalis (Mitchill, 1815), that regularly escape to streams, and from Ohrid trout, Salmo letnica (Karaman, 1924), and Arctic charr, Salvelinus alpinus (Linnaeus, 1758), stocked into streams and reservoirs. Risk of invasiveness that wild trout stocks are exposed to and their restoration were driving forces for this study. Materials and methods. Trout specimens from the Jerma River sampled in 2013 were additionally analysed for their mtDNA haplotype. The invasiveness potential of eleven alien trout species and strains introduced by stocking into wild brown-and Macedonian trout stocks in Serbia were assessed with the Fish Invasiveness Screening Kit (FISK).Results. Five of introduced trout species and strains were classifi ed as having a high risk (sensu lato) and two of them as having a high risk (sensu stricto) of being (or becoming) invasive. Conclusion. Progressively rising and insuffi ciently controlled fi shing and management with stocking of non-indigenous trout in wild brown trout stocks are the main current threats to the original diversity. Alien brown trout strains cross breed with native brown trout and incorporate into their stocks. Currently, feral rainbow-, brook-, and Ohrid trout reveal great invasive potential by naturalization in waters heavily stocked with them. The fi sheries measures aiming to control and/or to eradicate alien strains of brown trout involve the restriction of stocking, landing of trout suspected as of alien strain or species, as well as the stringent control of stocking material used for the restorative stocking. They are mandatory, regarding the conservational dependence of wild brown trout stocks. Keywords: fi sh, wild trout, hatchery strains, stocking, invasiveness, FISK, conservation, fi sheries management INTRODUCTIONIn the last ten years, the investigation of wild brown trout Salmo cf. trutta Linnaeus, 1758 stocks in Serbia (Fig. 1) has indicated high diversity in the watersheds of all three seas occurring in the region (Black-, Aegean-, and Adriatic seas). Marić et al. (2004) reported for the fi rst time the occurrence of Macedonian trout, Salmo macedoni...

Effect of the introgression of Atlantic brown trout, Salmo trutta, into Adriatic trout, Salmo farioides in a stream at the drainage area of the Adriatic Sea basin of Montenegro

“…In the Adriatic region, only MA, AD, and ME phylogenetic lineages are considered autochthonous (Giuffra et al 1994, Apostolidis et al 1997, Snoj et al 2000. The use of mitochondrial DNA (mtDNA) markers (Berg and Ferris 1984, Gyllensten and Wilson 1987, Bernatchez 2001, Suárez et al 2001, Snoj et al 2002, Sušnik et al 2004, Cortey et al 2004, Bardakci et al 2006, Turan et al 2011, Simonović et al 2015 and nuclear markers (Ferguson and Fleming 1983, Antunes et al 2002, Hashemzadeh Sagherloo et al 2012, Pustovrh et al 2014, Araguas et al 2017 revealed that the genus Salmo is genetically a highly structured taxon and therefore, effective conservation strategies need to be focused on the population level. Genetic screening of variation in brown trout, Salmo trutta Linnaeus, 1758, has been largely applied towards evaluating introgression of hatchery strains into wild populations (Hansen and Loeschcke 1994, Arias et al 1995, Largiadèr and Scholl 1995.…”

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

“…This is supported by the fact that Romanian rivers are exclusively inhabited by brown trout of the Danubian lineage (Popa et al, 2013). Brown trout of the At lineage have so far been found scattered in Serbia, e.g., in the Gradac River, in the main bed of the Danube River near Veliko Gradište (1059th river kilometer), in the Brankovačka River (Marić et al, 2006), and in the Jerma River (Simonović et al, 2015). Brown trout in streams of the narrower Iron Gate area have never been investigated for their mtDNA haplotypes thus far, only those from the Rečka and Vratna Rivers in the broader Iron Gate area (Marić et al, 2006).…”

“…There is no evidence of their natural occurrence south and southeast of the Alps; regardless, they predominate as native in the headwaters of the upper Danube in Bavaria and in numerous drainages of the Austrian Danube. One possible explanation for the presence of At haplotypes could be uncontrolled stocking with allochthonous, hatchery-reared brown trout of the Atlantic clade, which were introduced in this way into many streams and rivers throughout the Balkans (Marić et al, 2006;Jadan et al, 2010;Simonović et al, 2015) and Europe (Largiadèr and Scholl, 1996;Osinov and Bernatchez, 1996;Hansen et al, 2000;Weiss et al, 2000Weiss et al, , 2001. Two specimens of the same H3 haplotype were recorded in 2010 in the Danube riverbed by Marić et al (2012) near the city of Veliko Gradište at river kilometer 1059.…”

Alien freshwater fish species in the Balkans—Vectors and pathways of introduction

“…Supportive evidence for this can be found in the Danube River basin, that is introgression of alien At1 haplotype of Atlantic brown trout (Marić, Sušnik, Simonović, & Snoj, 2006), which caused the loss of intraspecific variability, following the introduction of alien strains and a change in genetic composition of native brown trout stock of Danube lineage (Simonović et al, 2014). Considering the impact of introduced foreign-sourced brown trout on native brown trout stocks in Serbia, brown trout of the Atlantic lineage was found to be the most invasive alien brown trout strain in Serbia (Simonović et al, 2015).…”

“…Stocking with alien species has been banned by legislation in many Balkan countries(in 2000 in Serbia; in 2001 in Croatia), although dispersal via the Danube River as a prominent southern Invasive Corridor (Bij de Vaate, Jazdzewski, Ketelaars,Gollasch, & Van der Velde, 2002) continues. However, unintentional introductions of alien fish species and alien trout strains(Simonović et al, 2015) still occur in certain countries, such as Serbia.…”