New spectral templates for rhodopsin and porphyropsin visual pigments

A four-parameter model of spectral sensitivity curves was developed. Empirical equations were designed for A(1)- and A(2)-based visual pigments with the main a-band maximum absorptions (lambda(max)) from 350 nm, near the ultraviolet, up to 635 nm in the far-red part of the spectrum. Subtraction of the alpha-band from the full absorbance spectrum left a "beta-band" described by a lambda(max)-dependent Gaussian equation. Compatibility of our templates with A(1)- and A(2)-based spectra was tested on the electroretinographic (ERG-derived) scotopic action spectra recorded in dogfish shark, eel, Prussian carp and perch. To more precisely estimate the accuracy of our model, we compared it with widely used templates for visual pigments. There was almost no difference between the tested models in fitting the above-mentioned spectral data. One of the advantages of our model is that in the fitting of spectral sensitivity data it uses non-transformed wavelengths and the shape of the curve remains the same for a broad range of lambda(max) values. Compared to multiparameter templates of other authors, our model was designed with fewer (four) parameters, which we believe can bring us closer to understanding the true nature of the absorption curve

NEKE BIOLOŠKE ODLIKE SOMA (SILURUS GLANIS) IZ AKUMULACIJE „UVAC”

Som je najveća primarno slatkovodna vrsta ihtiofaune Srbije i u staništima koja naseljava predstavlja vrhunskog predatora. Ova vrsta ne spada u nativnu ihtiofaunu u vodama Rezervata Uvac, a vreme introdukcije, količina i uzrasni sastav unetih riba su nepoznati. Generalno, podaci o biologiji prirodnih populacija soma u otvorenim vodama u Srbiji su siromašni i do sada ne postoje studije o populaciji u akumulaciji Uvac. Ciljevi ovog istraživanja su određivanje starosne i polne strukture populacije somova i njegove distribucije u akumulaciji. Definisane su tri zone akumulacije u kojima je vršeno uzorkovanje, i to: zona I (gornji kanjonski deo akumulacije), zona II (srednji deo akumulacije sa ulivima dve pritoke) i zona III (donji deo akumulacije u oblasti brane). Mrežarskim alatima ulovljeno je ukupno 20 somova. Među ulovljenim jedinkama 7 je bilo mužjaka, 9 ženki i kod 4 jedinke nije bilo moguće makroskopski odrediti pol. Dužina je varirala od 60-86 cm kod mužjaka; 66-113 cm kod ženki i 51-57.5 cm kod polno nezrelih jedinki. Težina ulovljenih primeraka kretala se u opsegu 993-4 000 g kod mužjaka; 1 520-9 000 g kod ženki; i 652-984 g kod polno nezrelih jedinki. Među mužjacima su dominirale jedinke starosti 3+, dok su kod ženki sve starosne klase bile jednako zastupljene (2+-7+). Sve polno nezrele jedinke su bile starosti 2+. Som u akumulaciji Uvac dominantno naseljava gornji (kanjonski) deo, a na osnovu starosne structure populacije pretpostavlja se da je som u akumulaciju introdukovan pre više od 10 godina

SEASONAL VARIATION OF FISH COMMUNITY IN RIVERS PEŠTAN AND BELJANICA

Terenska istraživanja obavljena su na rekama Peštan i Beljanica tokom 2011. i 2012. godine, i obuhvatila su analizu sastava i strukture zajednica riba. Rezultati ukazuju na dominaciju ciprinidnih vrsta riba. Zajednica riba na ispitivanim lokalitetima je pod intenzivnim opterećenjem, te su podaci ovih istraživanja od važnosti za očuvanje i zaštitu ribolovnog resursa (područja).Field research of rivers Peštan and Beljanica have been done during 2011 and 2012, and were surveyed for ichthyofauna composition and structure. The results indicate the dominance of cyprinid fish species. Data on fish species diversity of the researched localities under high pollution is of value for conservation and protection of fishery sources

Diet Analysis of the Amur Sleeper (Perccottus glenii) from the Danube River Drainage Channel (Serbia)

The stomach content of 277 Amur sleeper individuals has been analyzed to present its feeding habits. Fish were sampled using electrofishing from July to November 2017 in the Danube River drainage channel near Veliko Gradište (Serbia). Fish age was estimated by otoliths examination. Ingested prey organisms were identified to the lowest reliable taxonomic level. The biotic indices: vacuity index (VI), frequency of occurrence (F), abundance (Cn), index of importance (PV), Shannon’s diversity index (H’), and equitability index (Eh) were calculated. A total of 18 prey categories and 1144 individual prey were identified in the fish diet, dominantly aquatic macroinvertebrates. There were no significant difference in diet composition between sampling months as well as 0+, 1+, and 2+ age groups (both 3+ and 4+ had one individual). Only eight individuals were found with empty intestines, thus VI was low (2.9). In average, each fish had 4.1 prey items in their intestines. For whole sample, H′ was 1.84 and Eh was 0.64. Trichoptera, Ephemeroptera, and Gastropoda were the most frequent,dominant, and abundant. The greatest diversity of prey items was recorded for fish sampled in October as well as for 2+ individuals, and the lowest for fish from August and 0+ individuals

ASSESSMENT OF THE ECOLOGICAL STATUS OF RESERVOIRS IN PROTECTED AREA ″UVAC″ BASED ON THE FISH COMMUNITY

Istraživanja zajednica riba obavljena su u oktobru 2019. godine u akumulacijama Uvac, Zlatar i Radoinja na području Specijalnog rezervata prirode ″Uvac″. Ukupno je registrovano prisustvo 12 vrsta iz pet familija. U svim akumulacijama zabeležena je dominacija ciprinidnih vrsta. Vrednosti indeksa saprobnosti (S) varirale su od 1,87 (Radoinja) do 1,95 (Uvac), što odgovara β mezosaprobnim vodama II klase boniteta (umereno zagađene vode). Najveći diverzitet zabeležen je za akumulaciju Uvac, a najmanji za Radoinju. Akumulacija Radoinja imala je ekološki potencijal koji spada u III-IV klasu, dok je kod ostalih akumulacija zabeležena II-III klasa. Ekološki status u ispitivanim akumulacijama je zadovoljavajući.Ichthyofaunistic surveys were conducted in October at Uvac, Zlatar, and Radoinja reservoirs in the area of Special natural reserve ″Uvac″. The presence of 12 species from five families was recorded. The dominance of cyprinid species was recorded in all reservoirs. The values of the saprobic index (S) varied from 1.87 (Radoinja) to 1.95 (Uvac), which corresponds to β mesosaprobic waters of the II quality class (moderately polluted waters). The greatest diversity was recorded for the Uvac reservoir, and the lowest for Radoinja. Radoinja reservoir had an ecological potential that belongs to the III-IV class, while the other reservoirs had a II-III class. The ecological status in the studied reservoirs is satisfactory

DIET COMPOSITION OF BROWN TROUT (SALMO TRUTTA L., 1756) FROM THREE RIVERS WITHIN SPECIAL NATURAL RESERVE «UVAC»

Ispitivana je ishrana potočne pastrmke iz tri vodotoka na području Specijalnog rezervata prirode „Uvac”: Mali Uvac (gornji deo toka Uvca); Tisovica i Zlošnica. Aparatom za elektroribolov ulovljeno je ukupno 29 primeraka pastrmke (14 iz Uvca, 11 iz Tisovice i 4 iz Zlošnice). Pregled crevnog sadržaja obuhvatio je identifikaciju konzumiranih kategorija plena i njihovu brojnu zastupljenost. Na osnovu dobijenih podataka izračunati su indeksi učestalosti, abundantnosti i značajnosti za svaku od utvrđenih kategorija plena. Utvrđeno je da pastrmke iz istraživanih voda, u pogledu diverziteta plena, odlikuje relativno širok spektar ishrane. Generalno, pastrmke iz ovih voda pretežno se hrane akvatičnim beskičmenjacima, pri čemu larve Trichoptera predstavljaju najznačajniji element ishrane. Kao vizuelni predator, pastrmka ispoljava jasan afinitet ka krupnijem i mobilnijem plenu. Dobijeni rezultati, budući da se radi o relativno malim uzorcima prikupljenim tokom jednog mesečnog izlaska (septembar), mogu se smatrati preliminarnim i iziskuju dalja istraživanja.The brown trout (Salmo trutta Linnaeus 1756) inhabits almost all rivers and streams running through the area of Special Natural Reserve «Uvac» (southwest of Serbia). In some of them it represents the only present fish species, and studies of its diet are important issue to understand its biology. Analysis of its diet provides information on its trophic requirements, interactions with other species, and habitat use in the investigated ecosystem (Oscoz et al., 2005; Ruginis, 2008). There are numerous studies concerning feeding of brown trout in European waters and elsewhere (Kara and Alp, 2005; Osoz et al., 2005; Montori et al., 2006; Ruginis, 2008; and references therein). On the contrary, such studies are scarce in Serbia and, to the best of our knowledge, in last 25 years only one paper concerning this matter was published (Skorić et al., 2012). The aim of this study is to describe diet composition of brown trout in the three rivers within the area of the Special Natural Reserve «Uvac»

THE EVALUATION OF ECOLOGICAL STATUS OF SMALL MOUNTAIN- WATERS/STREAMS IN THE AREA OF RESERVE “UVAC” BASED ON FISH COMMUNITIES

Ihtiofaunistička istraživanja obavljena su na osam vodotokova na području Specijalnog rezervata prirode „Uvac”. Ukupno je registrovano prisustvo 15 vrsta iz 5 familija. Na osnovu vrednosti primenjenog indeksa saprobnosti vodotoci Uvac, Vapa i Kladnicu su svrstani u I-II klasu ekološkog statusa, Grabovica i Jablanica su II-III klasa, dok su Tisovica, Vrševina i Zlošnica kategorisane kao I klasa ekološkog statusa. Istraživane tekućice odlikuje prisustvo nativnih ihtiozajednica, što je od posebnog značaja za očuvanje originalnog diverziteta.Ichthyofaunistic surveys were conducted on eight small streams in the area of Special natural reserve ”Uvac”. A total of 15 species from 5 families have been identified. Based on the value of the applied saprobity index, watercourses Uvac, Vapa and Kladnicu are classified as I-II ecological status class, Grabovica and Jablanica are II-III class, while Tisovica, Vrševina and Zlošnica are categorized as I ecological status class. Native fish communities characterize investigated streams

Seasonal weight-length relationship of Amur sleeper (Perccottus glenii Dubowski, 1877) in the Danube River drainage channel

The Amur sleeper (Perccottus glenii), an indigenous species to the Russian Far East, northern China and the northern part of Korean Peninsula, has been considered an invasive alien species to European waters, where it may have negative impact on eggs and larvae of native fish species, on aquatic macroinvertebrate and larval amphibians. There were a few findings of the Amur sleeper specimens in Serbia during 2001-2003. The first record of established population was from the Danube River flood plain zone (1139 river km) in 2005. Our study includes 85 specimens collected in the Danube River drainage channel near Veliko Gradište (Serbia), in 2015-2016. The body length of specimens range from 35.78 mm to 140.68 mm, while the body weight range from 0.5 g to 40 g. Based on scale analyses, specimens have been determined at age of 0+, 1+ and 2+. The length-weight analysis does not show any differences between the regression slopes of samples from the two season

STRATIFIKACIJA POKAZATELJA KVALITETA VODE AKUMULACIJE „UVAC” (SEZONA SREDINA LETA – RANA JESEN 2017)

Cilj rada je da se opiše dubinska distribucija odabranih parametara kvaliteta vode (temperatura, koncentracija rastvorenog kiseonika, pH, konduktivitet i koncentracija hlorofila-a) u vodi akumulacije „Uvac” tokom sezone sredina leta – rana jesen 2017. godine. Tokom posmatranog dela vegetacione sezone vodu ove akumulacije odlikuje direktna termička stratifikacija.The aim of the study was to describe the depth distribution of selected water quality parameters (temperature, dissolved oxygen content, pH, conductivity and chlorophyll – a concentration) in the "Uvac" reservoir during the middle of the summer to early autumn 2017. During observed part of the vegetation season, direct thermal stratification of water was recorded. Depth distribution of other water quality parameters closely followed the thermal stratification

CHLOROPHYLL-A CONCENTRATION AND TROPHIC STATE INDEX OF "UVAC RESERVOIR"

Tokom četiri sezone (sredina leta, kraj leta, rana jesen i sredina jeseni) obavljeno je merenje koncentracije hlorofila-a duž vodenog stuba od 30 m (interval 2 m). Analizirano je variranje vrednosti kao i dubinska distribucija merenog parametra. Tokom perioda direktne stratifikacije akumulaciju odlikuje metalimnionski maksimum koncentracije hlorofila-a. Vrednosti TSI varirale su u opsegu 36,9 – 49,5 dajući indikaciju o oligotrofnom, odnosno mezotrofnom statusu akumulacije u zavisnosti od sezone.During 4 seasons (middle of summer, late summer, early autumn, middle of autumn) measurements of chlorophyll-a have been conducted, along a 30 m water column (2 m interval). Variability of chlorophyll-a concentrations and their vertical distribution were analyzed. During the thermal stratification period, maximal concentrations of measured parameter were recorded in the metalimnion layer. TSI values varied within 36.9 – 49.4, thus indicating oligotrophic and mesotrophic status of reservoir depending on season