Climate changes alter species composition in both aquatic and terrestrial ecosystems. For establishment of species in a fish community, dispersal barriers, habitat structure and interactions between species act as a filter. The aim of this study was to examine changes in the fish community in Lake Tåkern, Sweden, by repeating a test-fishing in a lake 40 years after a previous test-fishing. Special interest was directed towards the possible establishment of bream (Abramis brama) and (Cyprinus carpio) which recently had been found in the lake. In addition, a decline of the low oxygen tolerant species crucian carp (Carassius carassius) and tench (Tinca tinca) was expected. Test-fishing was performed in June and August 2019 and combined with analyses of Environmental-DNA from samples in September 2019. A comparison with the average catch of 1978-1979 together showed that all cyprinid species had decreased in 2019. The hypoxic tolerant crucian carp decreased 16-fold in numbers, which was expected due to fewer events of cold winters and hypoxia. One bream was caught from the test-fishing and was also detected through eDNA-analysis. The ecological status of the fish community was classified as moderate but showed a high proportion of piscivore percids contra cyprinids, compared to six other shallow lakes in Sweden with similar characteristics. The high proportion of piscivore percids is probably contributing to the stability of the present clear-water state of the lake.

<p>Hemometrijskim metodama (deskriptivna statistika, analiza glavnih komponenti, ve&scaron;tačke neuronske mreže i fazi optimizacija) analizirani su rezultati procesa osmotske dehidratacije mesa srebrnog kara&scaron;a, sa ciljem unapređenja efikasnosti osmotskog tretmana i pronalaženja optimalnih tehnolo&scaron;kih parametara.<br />Osmotski tretman se odvijao u tri osmotska rastvora (vodeni rastvor natrijum hlorida i<br />saharoze, kombinacija vodenog rastvora natrijum hlorida i saharoze i melase i melasa &scaron;ećerne repe) različitih koncentracija, na četiri temperature (10&deg;C, 20&deg;C, 35&deg;C i 50&deg;C) i pri tri vremena procesa (1, 3 i 5h). Posmatrani su sledeći odzivi sistema: gubitak vode, prira&scaron;taj suve materije, povećanje sadržaja suve materije, sniženje aktivnosti vode i promena sadržaja minerala (Na, K, Ca i Mg). Karakterizacijom osmotski dehidriranog ribljeg polupoizvoda, poja&scaron;njeni su efekti osmotskog tretmana i inovatinog osmotskog rastvora na senzorne osobine, hemijski i mikrobiolo&scaron;ki profil tretiranog mesa ribe. Rezultati ispitivanja pokazuju da se primenom procesa osmotske dehidratacije povećava gubitak vode, prira&scaron;taj suve materije i sadržaj suve materije u svim uzorcima mesa srebrnog kara&scaron;a. Za sva tri osmotska rastvora, najveće vrednosti dobijene su nakon 5 časova, pri najvi&scaron;im temperaturama i u najvećim koncentracijama rastvora.<br />Povećavanjem temperature procesa, koncentracije rastvora i vremena trajanja procesa, povećan je sadržaj posmatranih minerala u tretiranom mesu ribe. Rezultati<br />ANOVA testa pokazali su da na vrednosti posmatranih odziva statistički značajno utiču<br />sva tri parametra: vreme, temperatura i koncentracija. PCA analizom procesa utvrđeno je da su pri izračunavanju prve glavne komponente najveći uticaj imale vrednosti svih odziva osim aw vrednosti, dok je ona najvi&scaron;e uticala na proračun druge glavne komponente. Iako su modeli ve&scaron;tačkih neuronskih mreža kompleksniji od modela polinoma drugog reda, mreže su pokazale bolji učinak usled visoke<br />nelinearnosti razvijenih sistema. Primenom fazi optimizacije postignute optimalne vrednosti procesnih parametara za vodeni rastvor natrijum hlorida i saharoze su bile na nižim temperaturama i nižim koncentracijama rastvora, dok su za rastvore sa melasom &scaron;ećerne repe optimalne vrednosti na maksimumima posmatranih opsega temperature i koncentracije rastvora. Procesom osmotske dehidratacije smanjen je inicijalni broj bakterija u mesu srebrnog kara&scaron;a. Hemijskim i senzorskim analizama utvrđeno je da je melasa &scaron;ećerne repe zbog svog kompleksnog nutritivnog sastava<br />povoljnije je delovala na promenu hemijskog sastava i senzorne osobine uzoraka u odnosu na druga dva rastvora.</p> / <p>Chemometric methods (descriptive statistics, principal components analysis, artificial neural networks and fuzzy optimization) were used to analyze the results of osmotic dehydration of silver crucian carp, with the aim of improving the efficiency of the osmotic treatment and finding the optimal technological parameters.<br />The osmotic treatment was carried out in three osmotic solution (aqueous sodium chloride and sucrose solution, sugar beet molasses and the combination of these two solutions) of varying concentrations, at four temperatures (10&deg;C, 20&deg;C, 35&deg;C and 50&deg;C) and at three processing times (1, 3 and 5 h). The observed system responses were: water loss, solid gain, increase in dry matter content, reduction of water activity<br />and changes in mineral content (Na, K, Ca and Mg). The characterization of dehydrated fish, explained the effects of osmotic treatment on its sensory properties, chemical and microbiological profile. Results have shown that the application of osmotic dehydration increases water loss, solid gain and dry matter content in all samples of fish meat. For all three osmotic solution, the highest values were obtained after 5h, at the highest temperatures and in the highest concentration of the solution. By increasing the process temperature, concentration and time, increased the mineral content in the fish meat. The results of the ANOVA test have shown that the values of the observed responses significantly affect all three parameters: time, temperature and concentration. PCA analysis process has found that on calculation of the first principal component all response values except aw value had the greatest impact, while aw value had the most influence on the calculation of the other major component. Although models of artificial neural network models are more complex than second order polynomial, the network showed better performance due to the high nonlinearity of the developed system. Application of fuzzy optimization obtained optimal values of the process parameters for aqueous solution of sodium chloride and sucrose were at lower temperatures and lower concentrations of the solution, while the solutions with molasses optimal values of the maxima observed ranges<br />of temperature and solution concentration. The process of osmotic dehydration has reduced the initial number of bacteria in meat silver carp. Chemical and sensory analyzes have shown that the sugar beet molasses due to its complex nutritional composition has a better effect on changing the chemical composition and sensory characteristics of the samples.</p>