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The difference between the VTEC values obtained from the Global Navigation Satellite System (GNSS) and satellite altimetry is much more noticeable over the ocean and the sea due to less coverage of the GNSS observations. Previous research shows that differences can go up to 15 TECU. The main problem is calculating VTEC from raw data which is ambiguous. This paper presents filtering methods for estimating the differences between mentioned datasets. By using this solution, it is possible to achieve better accuracy on a global estimation of the deviation. The International Reference Ionosphere values were used for validation of the results.

This study aims to analyze the quality of several local reference quasigeoid surfaces obtained from several Global Geopotential Models (GGM) relative to the official quasigeoid solution of Serbia (SQM2011) and GNSS/dh observations for the territory of Serbia. Therefore, validation and comparison of the derived surfaces from the three GGM’s were made based on comparisons of height anomaly derived from GGM’s, SQM2011, and the GNSS/dh observations at the points of the high-precision leveling network. The selected publicly available GGM’s in this study are GOCO05c, SGGUGM-2, and XGM2019e. Primarily, at 1001 points of the high-precision leveling network, the differences between GGM and GNSS/dh height anomaly were calculated. The final translation parameters were calculated in the iteration procedure, which was then used to calculate the final values of the estimated height anomaly for all GGM’s at 143207 points of the regular grid of spatial resolution 0.5' × 0.5' on the entire territory of Serbia. From the estimated height anomaly, three GGM-derived surfaces were modeled relative to the SQM2011. According to the results of the calculations, SGG-UGM-2 provides the best approximation of the quasigeoid SQM2011, where the remaining differences have a mean value of 0.01 m, a standard deviation of 0.06 m, and a span of 0.67 m

This paper presents a research on students’ attitudes towards the use of Wikipedia in teaching. The sample was comprised of students from the Pedagogical Faculty in Vranje, a higher education institution affiliated with the University of Niš, Serbia. Students were assigned to write articles on Wikipedia as an alternative to writing their standard term papers. That way the Wikipedia content became significantly enriched. They positively evaluated Wikipedia as a teaching tool. The results confirmed that students preferred creating articles on Wikipedia to writing standard term papers. Those results may contribute significantly to further improvement and modernization of university teaching., Este artículo presenta una investigación sobre las actitudes de los estudiantes hacia el uso de Wikipedia en la enseñanza. La muestra estuvo compuesta por estudiantes de la Facultad Pedagógica de Vranje, una institución de educación superior afiliada a la Universidad de Niš, Serbia. Se asignó a los estudiantes a escribir artículos en Wikipedia como una alternativa a la redacción de sus trabajos de término estándar. De esa manera, el contenido de Wikipedia se enriqueció significativamente. Valoraron positivamente a Wikipedia como herramienta de enseñanza. Los resultados confirmaron que los estudiantes preferían crear artículos en Wikipedia a escribir trabajos de término estándar. Estos resultados pueden contribuir significativamente a una mayor mejora y modernización de la docencia universitaria.

Carp is the dominant species grown in Serbia and makes up over 80% of the total fish production. The aims of the present study were to analyze changes of protein, lipid, ash and moisture in dorsal muscle, adipose tissue and liver in common carp additionally fed complete pellets during four months in natural carp ponds. Twenty fish from four ponds were sampled. Analysis of variance showed that protein content was the highest in dorsal muscle and adipose tissue and was the smallest in liver (P < 0.05). The percentage of protein was quite stable and reached a plateau value (18.42–19.49%) in dorsal muscle. Total lipid content in common carp was the highest in liver (14.79–17.24%) and smaller in dorsal muscle (1.92–5.42%) (P<0.05). More interested were how the fish mass increased during breeding. The proximate composition of fish tissues was expressed as absolute content by weight of each fish. Simple regression resulted in relationships between protein content (g/fish) and body weight (g) indicating strong association (r = 0.965). Simple regression resulted in not strong relationships between lipid content (g/fish) and body weight (g (r = 0.784). There was a strong relationship between moisture content (%) and lipid content (%) (r = 0.962). The protein content (g/fish) was strongly associated with body weight in dorsal muscle and adipose tissue since coefficients of regression were high (>0.95), as were t-tests of significance (13.69, 18.04), and in the liver there was also an association since the coefficient of regression was 0.952 and the t-test was high (11.72).

In the last 60 years, pond farming of common carp (Cyprinus carpio) in Europe has gradually intensified, which has increased the stocking density and amount of supplementary feed, resulting in higher yields. Additionally, compound feed has been introduced to semi-intensive farming to increase the growth of farmed fish. Feed quality affects growth directly through conversion efficiency and indirectly by influencing fish physiology. In the present study, juvenile common carp were grown in net cages in a fishpond for 80 days and fed the same amount of different supplementary feed: wheat, pelleted, or extruded feeds or fish relied only on the available natural food (control group). Growth, microanatomy of the liver and distal intestine, and morphology of erythrocytes were evaluated. Compound feed had beneficial effects on the growth and histological parameters compared to the control group and fish fed wheat. This included higher surface areas of erythrocytes and hepatocytes` nuclei, longer intestinal folds, and thicker tunica muscularis in the distal intestine. The study showed that increased growth and use of compound feeds did not cause any physiological trade-offs that would be depicted in quantitative histomorphometry, and there was an absence of histopathological changes.

U cilju ostvarenja većeg prihoda po jedinici površine (zapremine) ribnjačkog objekta, proizvođači ribe se sve češće opredeljuju za intenziviranje proizvodnje. Intenzivnija proizvodnja najčešće podrazumeva veći broj nasađenih jedinki po jedinici površine/ zapremine proizvodnog ribnjačkog objekta. Veća gustina ribe po jedinici površine/ zapremine ima za posledicu pogoršanje kvaliteta vode u ribnjaku, smanjenje raspoloživog prostora za svaku gajenu ribu, potrebu za češće manipulacije sa ribom (probni izlovi, sortiranje i čišćenje ribnjačkih objekata), a to su ujedno i faktori stresa, koji ne retko, predstavljaju inicijalne okidače za razvoj različitih bolesti. Ukoliko navedenim stresorima dodamo i činjenicu da se u gušćim nasadima, bolesti lakše prenose sa jedne na drugu jedinku, jasno je da se intenziviranjem proizvodnje riba povećava rizik od obolevanja riba, a samim tim i od finansijskih gubitaka u proizvodnom procesu. Postavimo li pitanje da li se na drugi način može povećati prihod na ribnjačkim farmama, jedan od odgovora je svakako u diverzifikaciji korišćenja ribnjačkih farmi. Diverzifikacija ribnjačkih farmi podrazumeva korišćenje raspoloživog ribnjačkog prostora za druge oblike proizvodnje (poput gajenja kalifornijskih glista na pastrmskim ribnjacima, gajenja vodenih ptica na šaranskim ribnjacima, gajenja vodenih beskičmenjaka, gajenja ovaca i drugih vrsta domaćih životinja na nasipima šaranskih ribnjaka i proizvodnju električne energije) ili pružanja raznličitih usluga (ugostiteljstvo, lov, ribolov, plovidba, veslanje i turizam), čime se prihodi mogu značajno uvećati, a bez intenziviranja proizvodnje i povećanja rizika od bolesti riba.

Within this paper, we evaluated the quality of three Global Geopotential Models entitled: EGM96, EGM2008, and GOCO05c. The models were evaluated by using 1001 terrestrial discrete values of height anomalies determined by Global Navigation Satellite Systems and normal heights, which we considered to be true values within this research. In addition to the quality evaluation, we tailored the models by using more than 80000 free air anomalies. The results obtained from the evaluation and tailoring indicate that by using the GOCO05c it is possible to determine a set of anomaly heights across Serbia, which are in agreement with terrestrial values with an average value of -7 cm, the standard deviation of ±9 cm and with the range of 44 cm., У оквиру рада оцењен је квалитет три глобална гепотенцијална модела: EGM96, EGM2008 и GOCO05s. Квалитет модела је тестиран коришћењем 1001 условно тачних вредности дискретних вредности аномалија висина које су претходно одређене применом (комбиновањем) Глобалних навигационих сателитских система и нормалних висина. Поред наведеног, модели су и прилагођени територији Србије коришћењем више од 80000 аномалија слободног ваздуха. Резултати добијени из наведених одређивања указују да се применом модела GOCO05c могу одредити аномалије висина на територији Србије које апроксимирају терестрички одређене аномалије висина са средњом вредношћу од -7 cm, стандардном девијацијом од ±9 cm и то у оквиру распона од 44 cm.

Институт суспензивног вета председника републике сматра се једном од класичних тема уставног права, која до сада пак није побудила продубљеније интересовање наше уставноправне науке. Сразмерно томе колико је пажње у литератури посвећено неким другим председничким овлашћењима, може се рећи да је ситуација слична и када је реч о иностраним ауторима. Он пак заслужује већу пажњу и то не само због свог значаја у уставноправном поретку (ради се о овлашћењу које је важан чинилац међусобног односа највиших власти), већ и због чињенице да је теоријски гледано интересантан – услед свог порекла, те различите еволуције широм света, суспензивни вето се данас јавља у готово свим републикама на свету, али у веома различитој форми, са различитим одликама и сврхом. Из разлога такве хетерогености приметна су значајна одступања у дефинисању и теоријским квалификацијама овог института у доктринама разних земаља, које су по правилу окренуте „ка унутра“, тј. превасходно ка сопственом уставном решењу овог института. Закључци изведени таквим приступом су зато најчешће непримењиви универзално. Како уставно право као наука тежи да прикупи, обради и научно систематизује знања из своје области, извлачећи када је то могуће и генералне закључке, поставило се у писању овог рада питање да ли се конкретно институту суспензивног вета може прићи на начин који би успео да га у задовољавајућој мери објасни у читавом свету, једним универзалним приступом. Покушај давања одговора на ово питање је подразумевао опсежно упоредноправно и доктринарно истраживање пре свега са циљем изналажења објашњења шта је суспензивни вето, шта све он може да подразумева и какво његово дејство у конкретном систему може бити. Суспензивни вето је у САД, земљи у којој је у својој модерној форми и настао, данас једно моћно политичко средство у рукама председника, које чини важан елемент система „кочница и равнотежа“. Са друге стране, нпр. у Немачкој овај институт постоји у једној својој најсведенијој форми, која је обимом и квал, The institute of presidential veto is considered to be one of the “classical” topics of constitutional law. However it has not caused a more substantial interest in our doctrine. Considering the amount of attention given to other presidential powers in literature, one can conclude that there is a similar situation among foreign scholars as well. Nevertheless it certainly requires greater attention, not only for its significance for constitutional legal order (this power is an important element and determent of relations between highest powers), but also for the fact that it presents one interesting institute from the theoretical aspect – due to its origin and different evolution worldwide, presidential veto power is today present in almost all the republics in the world, albeit in rather different forms, with different features and purposes. Due to such heterogeneity, there are great variations in definition and theoretical qualifications of this institute in the doctrines of different countries, which are however by default turned primarily towards their own constitutional solution for this institute. The conclusions derived by such approach are therefore often not universally applicable. As constitutional law as a science strives to collect, process and scholarly classify the knowledge from its field, deriving general conclusions when possible, the author of this paper considered whether the institute of presidential veto could be observed in such a manner so as to sufficiently explain it worldwide, through one universal approach. The attempt to provide an answer to this question included a comprehensive comparative law and principled research, primarily with a view to explaining the meaning of presidential veto power, all its possible implications and possible effect in a particular system. In the US, being the country of origin of presidential veto in its modern form, it is a powerful political means in the hands of the president and an important element of the

Elevated concentrations of heavy metals in water can cause deformities of the mouthparts in chironomid larvae reared on artificial sediment. This investigation is an attempt to study effects of increased copper concentrations on mouthparts deformities of Chironomus plumosus larvae reared on natural sediment obtained from carp pond. Since the bioavailability of heavy metals is greater in artificial substrates than in natural ones usage of carp pond sediment, especially due to its low heavy metals content according to sediment quality guidelines, should provide more realistic assessment of biomarker potential of chironomid mouthparts deformities in biomonitoring of copper sediment pollution. It is demonstrated in the experiment that an increase of copper concentration in sediment leads to progressive increase in the frequency and severity of deformities of the mentum in C. plumosus larvae. Thus, shortening of median teeth in 2.0 +/- 0.2% individuals was the only deformity recorded in control tanks (at 15 mu gg-1 Cu), at 30 mu gg-1 Cu its frequency increased to 16 +/- 2%, and shortening of median-lateral teeth appeared at the same frequency, while at 60 mu gg-1 Cu frequency of both deformities increased to 24 +/- 2% and 28 +/- 4%, respectively, in addition to the appearance of tooth loss in 16 +/- 3% of individuals.

Предмет докторске дисертације су гарантије независности судија уставних судова. Оне представљају битну појаву у сваком друштву. Њима гарантујемо да ће одлуке које се доносе у уставним судовима бити донешене у складу са уставом и законима и правилима струке, без могућности уплива било каквих утицаја. Независност судија уставних судова можемо посматрати у теоријском, историјском и позитивноправном контексту. Ову појаву можемо изучавати кроз три вида вањски, унутрашњи и мјешовити, у зависности да ли независност посматрамо као однос судија уставних судова према спољним, унутрашњим или паралелно према оба наведена субјекта. Временски оквир истраживања је смјештен у период од 19. вијека до данас, јер се настанак функције контроле уставности везује за почетак 19. вијека. Просторни оквир истраживања су државе чланице Савјета Европе у којима постоје посебни уставни судови. Дисциплинарно истраживање можемо смјестити у уставноправну научну област, подобласт судска контрола уставности. Циљ истраживања је идентификација свих гарантија које су битне за независност судија уставних судова и проучавање на који начин дјелују на независност. Методи истраживања који се користе у овом истраживању су: нормативни метод, догматички метод, метод анализе садржаја, дедуктивни метод, индуктивни метод, метод анализе, метод синтезе, компаративни метод и историјски метод. Истраживање указује да независност судија има теоријски, историјски и позитивноправни контекст и вањски, унутрашњи и мјешовити вид. О независности судија уставних судова могуће је говорити само у државама гдје се поштује принцип подјеле власти. Историјски контекст независности видимо у еволуцији принципа подјеле власти и успостављању контроле уставности. У позитивноправном смислу најбоље рјешење је посебно и изричито нормирање кроз уставе и законе да су судије уставних судова независне., The subject of the doctoral thesis are guarantees of the independence of judges of the constitutional courts. This represents an important phenomenon in any society. It guarantees that decisions taken in the constitutional courts to be made in accordance with the Constitution and the laws and rules of the profession, without the possibility of any interference. The independence of judges of the constitutional courts can be considered in the theoretical, historical and legal context. This phenomenon can be studied through three types of external, internal and mixed aspects, depending on whether we consider independence as the relation of judges of the constitutional courts with external subjects, internal subjects or parallel with both. The time frame of the research is located in the period from the 19th century to the present, because the occurrence of judicial review in early 19th century. The spatial framework of the research are the Member States of the Council of Europe in which there are special constitutional courts. Disciplinary research can be placed in the scientific field of constitutional law, in the subfield judicial control of the constitutionality. The aim of the research is to identify all the elements that are essential to the independence of judges of the constitutional courts and study in what way they affect the independence. The methods of research used in this research are: normative, dogmatic, content analysis, deductive, inductive, analysis, synthesis, comparative and historical method. Research indicates that the independence of judges has theoretical, historical and legal context and external, internal and mixed aspect. The independence of judges of the constitutional courts can be considered only in the countries which respects the principle of separation of powers. Historical context of independence can be seen in the evolution of the principle of separation of powers and the establishment of judicial review. In legal context best solutio

This paperwork is dedicated to the research of the quality of height anomalies derived from the Global Geopotential Models GOCO over the Serbia territory. Three different types of approaches for the same model were considered: time wise, space wise and direct approach. The quality of the mentioned models is determined by comparison with terrestrial data of height anomalies, that are relate to the second high precision leveling network of the Republic of Serbia (the period of realization of tide gauges observations for determining the vertical position of the reference surface of the height reference system of the Republic of Serbia is 1971.0 years) and European Terrestrial Reference System 1989, realization ETRF2000, epoch 2010.63. By direct comparison, it was established that all models give almost identical data on the territory of Serbia and that with the application of the model one can approximate height anomalies at the territory of Serbia with a mean value of maximum 7 cm and with a standard deviation of 20 cm. Besides of this, models are compared in their spectral domains, with each other and with the model EGM2008, by comparison their degree and error degree variances.

This paper presents the combined method of determining the deflection of vertical components ? and ? based on the precise levelling and GNSS measurements. In general, there are several methods, but the combined method simplifies data collecting and subsequent processing of results in comparison with other methods. Components determination was performed on the high precision levelling network in Serbia, by calculating undulation on each point, so as azimuth and length for each side of the network starting from reference point. The length of sides is in the range of 20 km to 300 km. A point approximately located in the middle of the network was chosen as a reference point. By applying least-squares method, the estimated values of the components were obtained. In addition to the statistical evaluation of the deflection of vertical components, the paper shows a comparison of the obtained values with the values from the global Geopotential models, which justifies using the combined method for networks of similar design.

Šaran (Cyprinus carpio) je kao slatkovodna vrsta široko zastupljena kada je u pitanju farmsko gajenje riba u centralnoj i istočnoj Evropi. Na području Srbije, “klasična” poluintenzivna proizvodnja je dominantan tip gajenja riba, sa preko 95% ukupno proizvedenog šarana, a zasnovana je na kombinaciji prirodne i dodatne hrane (žitarica i smeša koncentrata). Kada je reč o gajenju različitih kategorija šarana u okviru jednog proizvodnog objekta, uglavnom se pristupa gajenju samo jedne kategorije. Razlog tome su jednostavniji i manji manipulativni procesi prilikom izlova kao i sama ishrana riba, naročito kad su u pitanju žitarice i ručno hranjenje. Cilj ovog istraživanja je bio da se analiziraju mogućnosti gajenja mešanog nasada različitih kategorija šarana u odnosu na gajenje samo jedne kategorije. Eksperiment je realizovan na proizvodnom ribnjaku OZZ “Despotovo“ iz Despotova. U toku jedne proizvodne sezone, na ribnjačkim površinama A, B i C, analiziran je uticaj kombinovanog i nezavisnog gajenja dvogodišnjeg (S1+) i konzumnog šarana (S2+) na proizvodne karakteristike u poluintenzivnom sistemu gajenja, upotrebom peletirane hrane. Na osnovu dobijenih podataka o masi riba i količine potrošene hrane, dobijeni su rezultati ostvarenog prirasta (BWG) i koeficijenta konverzije hrane (FCR). Gajenjem jedne kategorije šarana ostvaren je bolji BWG nego kombinovanim gajenjem dve uzrasne kategorije riba u okviru istog proizvodnog objekta. Rezultati ostvarenog prirasta pokazali su razlike između jezera (A = 2 287 kg/ha; B = 1 399 kg/ha; C = 988 kg/ha). Razlog tome je potencijal prirasta nasađenih kategorija riba, jer se kod S1+ ostvaruje oko 3 puta veći prirast nego pri gajenju starije kategorije (S2+). FCR je takođe bio najniži pri gajenju samo S1+ (2.26). Pri kombinovanom gajenju S1+ i S2+ vrednost FCR bila viša (2.41) nego u jezeru A, ali i znatno niža nego pri gajenju S2+ u jezeru C (3.2). Korišćenje peletirane hrane sa višim sadržajem proteina (35/7), dodatno je uticalo na postiz

Независност земаља Латинске Америке наступила је као својеврсни ехо револуција у Северној Америци и Француској. Стога је и писана уставност, као супротност дотадашњој апсолутистичкој власти вицекраљева представљала „чедо“ галопирајућег и надолазећег либерализма. У Аргентини, Мексику, Венецуели и Бразилу она је уско скопчана и са федералним уређењем - као додатним механизмом за вертикално ограничавање централне власти. Територијално пространство, границе колонијалних провинција и идеолошки разлози представљали су добар основ за рецепцију северноамеричког уставног модела, који је поред федерализма укључивао и председнички систем. Међутим, милитаристичка традиција снажних обласних господара и одсуство политичке културе резултираће бројним деформацијама овог модела-узора. Неоколонијални положај зависности довешће до економског заостајања Латинске Америке за земљама „центра“ те дубоким друштвеним поделама. Политичка нестабилност читаве регије биће појачана и спољним фактором, те ће током друге половине XX века читава регија постати позорница хладноратовских чарки. Сва три начела федерализма у великој мери су нарушена као колатерална штета војних хунти и централизирајуће економске политике развоја. Крај осамдесетих година обележен је јењавањем насилних пучева и постепеним повратком на демократске процедуре. Превазилажење огромних регионалних дисбаланса захтевало је да се приликом доношења одлука на савезном нивоу јасно чује и глас федералних јединица. Са редемократизацијом и потребом за ефикаснијим привредним управљањем и „зупчаници федерализма“ стидљиво покренути. Сам процес је скопчан са бројним потешкоћама, те је текао неједнако у свакој од четири поменуте земље. И док је у једнима до тада празна „уставна љуштура“ испуњена новим садржајем, дотле је у другима додатно огољена кроз још снажнију концентрацију одлучивања у центру. Специфичности државне структуре и динамични односи центрифугалних и центрипеталних сила дају подстрек ка истраживању уставних оквира и државних у, The independence of Latin Amеrican nations was a chain reaction of the revolutions in North America and France. Consequently, written constitutions, as opposite to the former absolute powers of viceroys, became the “child“ of galloping and upcoming tide of liberalism. In Argentina, Mexico, Venezuela and Brazil, this was also related with the federal arrangements - as an additional mechanism for vertical constraining of central government. Territorial vastness, former colonial borders of provinces and ideological reasons were steady grounds for reception of North American constitutional framework, which beside the federalism, includes the presidential system. However, militaristic regional strongman tradition and absence of political culture resulted in many deformations of original role model. Neocolonial position of dependence triggered off economic stagnation in comparison to a central core of capitalist countries and accompanying serious social disruptions. Political instability in the region was additionally increased with the external factor, and the whole of the area became a platform for a string of Cold War scrimmages during the second half of 20th century. All three principles of federalism was mostly infringed as a collateral damage of military juntas and centralizing development policies. The end of the 80`s was marked with the decrease in the number of violent putsches and with the gradually recovery of democratic procedures. For overcoming of vast regional imbalances it was necessary to hear the voice of federal units during the national decision-making processes. With the democratization and necessity for efficient economic management, “the gear weels“ of federalism carefully began to spin round. The process was linked with many difficulties, so it went in a different ways depending on the country concerned. Although in some cases until then empty “constitutional shells“ was filled with new contents, other countries additionally striped it naked with t

This paper presents the determination of the vertical deflection components using the Global Geopotential Model EGM2008. The components are defined in two groups of points: 4083 points are relatively correctly distributed across the territory of Serbia and 46 Laplas and geoid points defined in Serbia in the past century, from the set of institutions. All presented determinations in this paper are related to the Geodetic Reference System 1980 (GRS80), with the coordinates of all the points used to refer to the International Terrestrial Frame 1996 (ITRF96). Analysis of the results of the determination showed that the EGM2008 can be used to approximate the astrogeodetic determination with the agreement of several arc seconds., U okviru rada prikazano je određivanje komponenti odstupanja vertikala primenom Globalnog geopotencijalnog modela EGM2008 (Earth Gravitational Model 2008). Komponente su određene u dve grupe tačaka: 4083 tačke relativno pravilno raspoređene po teritoriji Srbije i 46 Laplasovih i geoidnih tačaka koje su određene u Srbiji u prošlom veku, od stane niza institucija. Sva prikazana određivanja u okviru rada odnose se na Geodetski referentni sistem 1980 (Geodetic Reference System 1980 - GRS80), pri čemu se koordinate svih korišćenih tačaka odnose na Međunarodni referentni okvir za epohu 1996 (International Terestrial Frame 1996 - ITRF96). Analizom rezultata određivanja pokazano je da se EGM2008 može koristiti za aproksimaciju astrogeodetskih određivanja sa saglasnošću od nekoliko lučnih sekundi.

The aim of this study was to assess the accumulation and seasonal variations of 20 toxic and trace elements in the abdominal and dorsal muscle (DM), liver and gut contents (GCs) of Cyprinus carpio, and in the sediments and zooplankton from semi-intensive aquaculture ponds during a six-month production season (from May to October). Sediments showed the highest concentrations of the measured elements, followed by zooplankton, fish GCs and livers, while the lowest levels were present in fish muscles. Correspondence analysis revealed that the elemental composition of the fish GCs was mostly similar to that of the sediment and zooplankton. The element concentrations of carp liver and muscles were more similar to each other. Overall, the results indicate that fish liver was the main target organ accumulating Cu, Se and Zn, regardless of their initial amounts in the environment. A seasonal decrease of a range of elements in fish liver (Al, Co, Fe, Li, Mn, Ni, Pb and Sr) was evident towards the end of the investigation period. In addition, the fish DM showed a seasonal accumulation of Sr and Li. However, toxic elements i.e. As, B, Ba Hg and V did not show such a seasonal variation, and were evenly distributed between fish liver and muscles. The concentrations of some elements, such as As, in fish tissues were similar or even higher than in literature data from polluted sites, but none of them exceeded the maximum acceptable concentrations prescribed by Serbian legislation or by FAO or EU regulation.

Aquaculture is a type of food production with the highest rate of growth. Each year, compared with the previous, 9% more aquatic organisms are produced. Considering limited fish catch from world seas, increased consumption, as well as human population increase on the planet, it is realistic to expect that in the next period the need for fish from aquaculture will raise from year to year. However aquaculture importance is not only as food supply, but also reproduction and culture (farming) of aquatic organisms in order to protect and preserve endangered species of aquatic organisms in natural water ecosystems. Out of approximately 100 fish species inhabiting waters of the Republic of Serbia, 63 are under certain regime of protection (34 species in the status of "strictly protected" wild fish species and 29 wild species in the status protected"). Reasons for decrease of fish diversity in Serbia are many: often there is influence of various factors, seldom one can be sorted out as dominant. Factors most often influencing one or more fish species can be grouped as those originating from changes in the biotope, water quality deterioration, arrival of alochthonous fish species, spreading of diseases and increased pressure on fish resources from men and piscivorous animals. After elimination of factors endangering fish diversity, processes of natural recovery of the biocenosis, primarily fish fauna, mainly requires a long period. However natural recovery not only lasts too much, but this process can be unstable since fish abundance may vary, sensitivity can increase due to different reproductive characteristics, and different fish species have different diseases resistance. All this make natural recovery vulnerable to the negative influences. In such situation it is advisable to help endangered aquatic ecosystems. Among most simple ways, sometimes unique, is restocking with fish obtained from aquaculture. Aquaculture is of greatest importance for endangered fish species pr

Carp is cultured in all the 3 systems: extensive, semiintensive and intensive. Contrary to extensive rearing where weight gain depends exclusively on natural food, semiintensive and intensive systems are based on partial or complete reliance on added feed. During the rearing season the natural food in fish ponds with the semiintensive system has a prominent seasonality: in the period of natural food depression with optimal temperatures for carp growth (from mid June to the end of August) weight gain is primarily dependent on the quality and quantity of added feed. From an economical, and also an ecological point of view it is important to supply feed that will meet nutritional requirements of fish, and result in low feed conversion coefficient, high growth rate, good health condition, high quality of the final product – fish meat, and as low as possible load of the aquatic environment with organic matter, phosphorus, and nitrogen. Nutritional properties of fish feed are highly dependent on the protein and fat level. It is of utmost importance to stress that the amount of basic components in feed should not be fewer than the requirements of farmed fish, though, particularly from the economic point of view, this amount should’t be too high since the fish will not be able to utilise it. As the main building blocks, proteins are essential for body growth and a number of physiological processes. Their origin and quantity in feed mixtures are of crucial importance for the utilization of feed and growth of cultured fish. Fishmeal is the most desirable component of the feed that provides proteins with good amino acid composition in feed for carnivorous fish species, as well as for omnivorous fish in intensive production. Due to the deficit of this very important nutrient at the world market and their high prices, fishmeal and other feed of animal origin are combined or replaced with alternative sources of plant proteins. There is a constant tendency towards decreasing the s, Šaran se gaji u sva tri sistema gajenja: ekstenzivni, poluintenzivni i intenzivni. Za razliku od ekstenzivnog gde prirast ribe iskljuĉivo zavisi od prirodne hrane, poluintenzivni i intenzivni sistemi su bazirani na delimiĉnoj ili potpunoj zavisnosti od dodatne hrane. Kako tokom sezone gajenja, prirodna hrana u ribnjacima sa poluintenzivnim sistemom ima veoma izraţen sezonalni karakter, u periodu sa optimalnim temperaturama za rast šarana (od sredine juna pa do kraja avgusta) prirast je u najvećoj meri zavistan od kvaliteta i koliĉine dodatne hrane. Sa ekonomskog, ali i ekološkog aspekta vaţno je obezbediti hranu koja će zadovoljiti nutritivne potrebe riba, rezultirati niskim koeficijentom konverzije, visokim tempom rasta, dobrim zdravstvenim stanjem gajenih riba, visokim kvalitetom finalnog proizvoda, odnosno ribljeg mesa i što manjim opterećenjem vodene sredine organskim materijama, fosforom i azotom. Nutritivna svojstva hrane za ribe u velikoj meri zavise od udela proteina i masti. Veoma je vaţno da osnovnih komponenti u hrani za ribe ne bude manje od potreba gajenih riba, ali i sa ekonomskog aspekta da ih u hrani ne bude više od koliĉine koju ribe mogu iskoristiti. Proteini kao gradivne komponente, su veoma vaţni za izgradnju tela ali i za brojne fiziološke procese u organizmu. Njihovo poreklo, sastav, kao i koliĉina u smešama od presudnog su znaĉaja za iskoristivost hrane i prirast gajenih riba. Najpoţeljnija komponenta, kao nosilac proteina odgovarajućeg aminokiselinskog sastava, za proizvodnju hrane za karnivorne vrste riba, ali i za intenzivno gajenje omnivornih riba je riblje brašno. Zbog deficita ovog veoma vaţnog hraniva na svetskoj pijaci i visoke cene na trţištu, riblje brašno, kao i ostala hraniva animalnog porekla se kombinuju ili pak potiskuju sa alternativnim biljnim izvorima proteina, uz optimizaciju koliĉine u obroku i uz stalnu teţnju da se što veći procenat ribljeg brašna potisne iz hrane. Masti prisutne u hrani doprinose efikasnijem iskorišćavan

U uslovima intenzivnog gajenja kalifornijske pastrmke (Oncorhynchus mykiss), troškovi ishrane čine 50 do 70% ukupnih troškova u proizvodnji. Tokom višegodišnjih istraživanja, došlo se do zaključaka da proteinska hraniva biljnog porekla u određenoj meri mogu da zamene riblje brašno (FM) i smanje troškove proizvodnje. Najčešće korišćeni biljni proteini u ishrani riba su sojini proizvodi. Međutim, uspešnost zamene ribljeg brašna zavisi od vrste ribe koja se gaji, uzrasta riba kao i tipa korišćenog sojinog proizvoda. Kao jedan od boljih alternativnih izvora proteina navodi se sojin proteinski koncretat (SPC). SPC se dobija ekstrakcijom proteina iz sojinog brašna i sadrži oko 70% proteina. U akvakulturi predstavlja dobru zamenu za riblje brašno, jer sadržaj i svarljivost proteina u SPC su slični kao u FM. Neutralnog je ukusa i standardno je dobrog kvaliteta u odnosu na promenljiv kvalitet FM. Istraživanje je sprovedeno u „Centru za ribarstvo i primenjenu hidrobiologiju“ ODPF Radmilovac. Mlađ kalifornijske pastrmke, prosečne nasadne mase 33,62g, hranjena je smešama koncentrata (44/20 Extra, proizvođača Veterinarski zavod Subotica) sa različitim procentualnim učešćem FM:SPC, i to: 100:0, 75:25, 50:50, 25:75 i 0:100. Na osnovu dobijenih rezultata, nakon 60 dana hranjenja riba smešama koncentrata sa različitim učešćem FM i SPC, mogu se konstatovati statistički vrlo značajne razlike u masi i dužini tela. Najbolju završnu masu, kao i BWG, SGR, TGC i FER uz najmanji FCR imale su ribe hranjene smešom gde je odnos FM:SPC bio 75:25. Nasuprot tome, ribe hranjene smešom koncentrata bez učešća FM, imale su statistički vrlo značajno niže vrednosti BWG, SGR, TGC i FER, pri čemu je FCR bio statistički vrlo značajno veći nego upotrebom drugih smeša. Dobijeni rezultati ukazuju da je u ishrani mlađi kalifornijske pastrmke najopravdanije koristiti smešu u kojoj je odnos FM:SPC bio 75:25, kako zbog proizvodnih rezultata tako i zbog smanjenja cene koštanja samog proizvoda.