Vera Nikolić

Re‐evaluation of Salmo data by Gridelli (1936)—description of stocking, hybridization and repopulation in the River Soča basin

History of stocking in Salmo marmoratus habitat in the Adriatic region and its effects are poorly known due to data deficiency. Well‐documented research from 1936 based on trout external morphological characters was compared with research of extant trout populations based on genetic markers in an attempt to clarify the impact of stocking in the River Soča basin. Application of multivariate statistical methods reveals a similar pattern of native and non‐native trout distribution in 1936 and after a recently started S. marmoratus repopulation project. Remnants of initial stocking from 1906 were detected in one stream in the upper Soča basin. Gridellis samples of S. dentex, one of the least researched trout species of the Adriatic region, were also re‐analysed and were found to differ from all other trout populations used in the study.

RISKS TO STOCKS OF NATIVE TROUT OF THE GENUS SALMO (ACTINOPTERYGII: SALMONIFORMES: SALMONIDAE) OF SERBIA AND MANAGEMENT FOR THEIR RECOVERY

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.

Molecular and ecological features of the soft-muzzled trout Salmo obtusirostris (Heckel, 1852) in the Zeta River, Montenegro

This paper reports about the occurrence of soft-muzzled trout in Montenegro. It was found only in the Zeta River, at three localities, always in low abundance. Results of genetic investigation on twelve microsatellite loci (i.e., high Fst and high heterozygozity values) as well as lack of hybridization with the putative brown trout unequivocally confirm that the soft-muzzled trout from the Zeta River is a species distinct from the putative brown (Salmo cf. farioides) and marble (Salmo marmoratus) trout that live in sympatry with it. This paper also confirms high genetic diversity of Zeta River soft - muzzled trout population. Habitat and feeding analyses revealed that soft-muzzled trout reduce the competition with syntopic putative brown trout by displacing as the bottom-dweller in their common type of habitat, as well as by narrowing its feeding niche and feeding dominantly with the benthic macroinvertebrates, the Gammarus shrimps as their far dominant feeding item. Results also revealed that they did not share the same habitat with marble trout. Due to this population low abundance and their importance on species level, Zeta River soft-muzzled trout conservation needs are urgent in terms of in situ protection and repopulation measures.

Ichthyofauna of the River Sava System

On the survey of the recent records, the fish and lamprey fauna of the River Sava catchment consists of 74 species, 15 of which being considered alien. The indigenous species diversity, explained using the relation N = 0. 546 A 0.232, fits well into the range common for large catchments in Europe. Both taxonomic and ecological diversity, as well as the character of fish communities in streams and rivers, are strongly correlated with the stream order. On the relative abundance of species in fish communities, the upper rhithron fish communities cluster distinctly from those belonging to the middle rhithron, within which several subgroups of fish communities were distinguishable. Fish communities of the middle rhithron character in streams and small rivers stand distinctly apart from those belonging to particular sections of large rivers (e.g., the Rivers Sava, Drina, Vrbas, and Bosna), with the transitional type of middle rhithron fish community in larger rivers (e.g., those in the Rivers Una and Sana) that resemble more to the fish communities common in middle rhithron streams. Fish communities in the middle section of the River Sava in Croatia and in the bordering area with Bosnia and Herzegovina mainly belong to the lower rhithron, attaining the character of potamon in the most downstream, Serbian section. River Sava’s fish communities strongly interact with the ones occurring in the most downstream sections of their largest tributaries, e.g., the Rivers Una, Vrbas, Bosna, Drina, and Kolubara, which makes them very similar in structure in the areas of river mouths. Classification of fish communities based solely on the presence and absence of species revealed similar general pattern of fish community classification, though with the more sharp delimitation between those belonging to the upper and middle rhithron on one and to the lower rhithron and potamon on the other side. That was supported by the determination of fish communities belonging to the upper rhithron with brown trout Salmo cf. trutta, European bullhead Cottus gobio, and minnow Phoxinus phoxinus as the most common fish species. Fish communities belonging to the middle rhithron were determined mainly with chub Squalius cephalus and spirlin Alburnoides bipunctatus, whereas brook barbel Barbus balcanicus and stone loach Barbatula barbatula occurred in both upper rhithron and middle rhithron. Nase Chondrostoma nasus were associated with both middle and lower rhithron fish communities. The most common fish species that determine the lower rhithron fish communities were common bream Abramis brama, ide Idus idus, and bleak Alburnus alburnus, with the northern pike Esox lucius, Balon’s ruffe Gymnocephalus baloni, and racer goby Neogobius gymnotrachelus as significant species explaining fish communities of both lower rhithron and potamon. The level of production of fish in the River Sava varies remarkably within the sections with the similar ecological features, as well as between the sections that differ for the type of fish community. The greatest biomass and annual natural production were recorded in the sections homing the potamon and lower rhithron fish communities, especially in the flooding areas of side arms and oxbows which serve as spawning areas and nurseries. A total of 15 alien fish species was recorded in the River Sava catchment, the Prussian carp Carassius gibelio and brown bullhead Ameiurus nebulosus being assessed the most invasive in the areas with the potamon fish community. A strong impact from both long-term and recent stocking with alien hatchery-reared brown trout strains and rainbow trout in the upper rhithron fish communities was recently recognized. Mudminnow Umbra krameri and huchen (or Danube salmon) Hucho hucho are considered the two most threatened fish species of the River Sava catchment, where various types of riverbed modifications, especially the damming, were seen the most prominent threatening factors for fish diversity.

Length-weight relationship in adult huchen Hucho hucho (L., 1758) from Drina River, Serbia

Huchen Hucho hucho from the Drina River (Serbia) revealed recently the decrease in breakpoint values for both standard length (Sl) and weight (w) in relation to the values recorded in 1999 from 110 cm to 98.4 cm and from 16.5 kg to 10.5 kg, respectively. That might indicate to the change in certain population parameters that could have an influence to the growth in the adult period of life.

Occurrence of Chilodonella hexasticha (Ciliophora, Protista) on farmed rainbow trout (Oncorhynchus mykiss) throughout the season.

An examination of rainbow trout Oncorhynchus mykiss for ectoparasites, on three not so distant fish farms with independent water supply in Eastern Serbia from March to November 1998, resulted in finding three ciliate (Chilodonella hexasticha, Ichthyophthirius multifiliis, Apiosoma piscicola var. minor), one trematode (Gyrodactylus sp.) and one mould (Saprolegnia sp.) species, making a total of five parasite species. The Chilodonella hexasticha was recorded only on one of the farms, being in the highest extensity in May. This appeared to be the most prominent occurrence in the independent pattern of infestation dynamics of other parasites (Apiosoma, Gyrodactylus, Saprolegnia) recorded on that fish farm, as derived by Correspondence Analysis. The Friedman ANOVA test revealed a significant difference in extensity of occurrence of different parasites through the season, due to the significantly greater infestation with Gyrodactilus and significantly lower extensity of infestation with Saprolegnia.

Diversity of brown trout Salmo cf. trutta in the River Danube basin of Western Balkans as assessed from the structure of their mitochondrial Control Region haplotypes

The part of the River Danube basin in the Western Balkans region (11 sampled localities and 57 in total with using of published data) revealed the remarkable diversity of brown trout assessed using the Control Region (CR) of mitochondrial DNA (mtDNA) as a molecular marker. The greatest number of brown trout populations holds brown trout of the Da1 haplotype. Particular distinct haplotypes are limited to isolated brown trout stocks. There are haplotypes of Danubian (Da), and those of Atlantic (At), Adriatic (Ad) and marmoratus (MA) lineages introduced there. Phylogenetic relationships inferred between them implicate the plesiomorhic character of Da*Vr, Da*Dž and Da-s6 haplotypes that were resolved as ancestral clades, with the intermediate position between clades holding haplotypes of the non-Danubian lineage and more advanced haplotypes of the Danubian lineage. A uniform rate of evolution was found for all clades. The recent widespread distribution and exclusivity of Da1 haplotype imply its ancestral character among advanced Danubian haplotypes. Populations in the Sava, Drava, Una and Drina revealed an expansion, whereas those in the Kupa and Zapadna Morava catchments revealed both stability in size and great differentiation. Gene flow between stocks was found to be negligible.

SOCIAL, ECONOMIC, FISHERY AND CONSERVATIONAL ISSUES FEATURING FLY FISHING COMMUNITY IN SERBIA

Modern fly fishing, mainly for brown trout and grayling, has been done on a local scale and in low extensity in Serbia for over 50 years. Data obtained from 117 fly fishermen filling out an online questionnaire, with 30 questions processed using multivariate analysis, revealed that most fishermen who had started fly fishing since 2000 were under 40. Only few who were under 20 started to fish initially with the fly fishing equipment. They turned up committed to and skilled in fly fishing. Most of them live in large municipalities with much better economic opportunities. Their level of education is above average in Serbia. Economic power, place of residence and level of education outline their fishing capabilities, frequency of fishing outings, distance they travel to fly fish, as well as their attitudes towards fishery policy, conservation of native brown trout and grayling stocks, management of streams and communication with other fly fishermen. CODEN RIBAEG ISSN 1330-061X

Analysis of genetic structure of huchen (Hucho hucho) in Serbia inferred from mitochondrial and nuclear DNA.

Abstract The purpose of this study was to assess the genetic diversity of Serbian huchen and provide guidelines for conservation and management. Fourteen huchen individuals were collected from six localities. For all individuals the mitochondrial DNA control region and the NADH1 gene were sequenced, and two microsatellite loci were genotyped. Sequencing of two mtDNA loci showed the presence of the same haplotypes (Hh_CR_1 and Hh_ND1_1) in all investigated specimens and the complete absence of genetic variability at inter- and intra-populational level. However, analyzed individuals from Serbia have the largest number of control region repeats (average 8.7) compared to all other huchen populations from the Danube basin. Microsatellite data show that the most of Serbian huchens were placed in the “eastern” cluster except one individual from the Drina River which clustered with “western” samples, most likely a consequence of stocking. In spite of only two loci used, four unique alleles found in the studied Serbian and Drina basin population indicate that the Danube basin may possess more region specific alleles than previously thought, which could be of great importance for efficient species management in the future. Abstract Cilj ovoga rada je bio da se izvrši procena genetičkog diverziteta mladice u Srbiji, i da se na osnovu dobijenih rezultata daju preporuke za buduće očuvanje i upravljanje fondom mladice. Za ovu svrhu sakupljeno je 14 jedinki sa šest lokaliteta. Za sve sakupljene jedinke sekvencirana je kontrolna regija, NADH1 gen mitohondijske DNK i genotipizirana su dva mikrosatelitska lokusa. Sekvenciranjem dva mtDNK lokusa utvrđeno je prisustvo istih haplotipova (Hh_CR_1 i Hh_ND1_1) kod svih ispitanih jedinki, odnosno, potpuno odsustvo genetičke varijabilnosti na inter- i intra-populacionom nivou. Međutim, analizirane jedinke iz Srbije karakterišu se najvećim brojem ponovaka kontrolne regije (prosečno 8,7), u poređenju sa svim ostalim populacijama mladice iz dunavskog sliva. Analizom mikrosatelitskih podataka, utvrđeno je da se gotovo sve jedinke iz Srbije svrstavaju u “istočnu” grupu, izuzev jedne jedinke iz Drine, koja je svrstana sa “zapadnim” uzorcima, što je najverovatnije posledica poribljavanja. Kod analiziranih jedinki sa teritorije Srbije i iz celokupnog sliva Drine pronađena su četiri jedinstvena alela, uprkos analizi samo dva mikrosatelitska lokusa. Dobijeni rezultati ukazuju da dunavski sliv može posedovati više regionalno specifičnih alela nego što se ranije smatralo, što bi moglo biti od velikog značaja za uspešno upravljanje fondom mladice u budućnosti.

Morphological differentiation of trout (subf. Salmoninae) based on characteristics of head skeleton

Abstract Investigation of trout (subf. Salmoninae) for their continuous osteological characters of head that included analyses of elements from skull and visceral (jaws, gills and gill covers) bones revealed the unambiguous distinction between the autochthonous and admixed brown trout Salmo trutta stocks of the Danube River drainage area in Serbia for the characters on vomer, skull height, pterotic and premaxilar bones. Rainbow trout Oncorhynchus mykiss and Ohrid Lakes belvica trout Salmo (Salmothymus) ohridanus were also examined as outgroup taxa in order to understand better the overall variability and to reduce bias in the methodology applied. Belvica trout were more similar to the admixed than to the autochthonous brown trout populations, especially concerning the characters on the bones of the skull. Rainbow trout appeared clearly distinct from all brown trout (autochthonous and admixed) on their elements of skull (its height and width at the sphenotic level), being similar to the autochthonous brown trout on the elements of visceral skeleton, whereas on the elements of visceral skeleton, belvica trout were the most distinct from the brown trout and the rainbow trout, mainly due to the difference in the length of the premaxilar and maxilar bones.