Repopulacija linjaka Tinca tinca L. 1758 (Osteichthyes:Cyprinidae) u šaranske ribnjake i otvorene vode / Repopulation of tench Tinca tinca L. 1758 (Osteichthyes:Cyprinidae) into carp fish ponds and open waters

Tench Tinca tinca (L., 1758) is a cyprinid fish species for which a drastic decrease in number in open waters was detected, as well as complete exclusion from fish ponds in Serbia. As this species is native for our country, for some time now attention was given to its repopulation and its popularization in aquaculture. While working on defining the most suitable methods for the repopulation of this species in open waters and fish ponds, the aims of this study were to define the most suitable methods for repopulation and define the most appropriate methods for cultivation of tench of various age. Possibilities of in situ and ex situ conservation are discussed, as well as application of PRC-RFLP analysis in controling the selection of broodstock and possibilities of using cryopreservation in forming gamete banks for this species.PCR-RFLP analysis enabled the detection of origin of analyzed individuals and thei assigment to major tench phylogroups (eastern and western) which can in the future be used as one of criterion during artificial spawning. Analysis of variability of mitochondrial markers indicated that the Danube River is a natural barrier between the eastern and western phylogroups, while analysis of nuclear markers indicated the natural invasion of the western phylogroup. Analysis of mitochondrial markers also displayed the presence of a haplotype which denotes the rare western W2 phylogroup. In this study, the application of cryopreservation on fish gametes was considered for the first time on the territory of Serbia. Introduction of this modern method expands the possibilities of cultivation and selection of broodstock in aquaculture, as well as enables the formation of gene banks for native species. Experiments conducted on tench sperm determined the effects of different extenders and cryoprotectants on the viability of spermatoids and their motility and fertilization potential. Experiments conducted indicated that the Grayling extender is the best extender for cryopreservation of tench sperm, while there was no significant difference between methanol and DMSO as cryoprotectants.The most effective method for evaluation of maturity of gonadal follicles and readiness  of females for spawning, when considering the batch spawning of tench, is the histological method. Histological analysis displayed asynchronous maturation of follicles, indicated that vitellogenesis started during April and that at least one batch of eggs was released until July, as well as that one more will most likely be released.By monitoring the early development of tench, description and periodization of this process was possible. By comparing the development of tench with other cyprinid species, few specificities arose. The analysis of early development showed that morphogenesis is not finished with hatching, and that formation of jaws and pectoral fins, opening of the mouth and inflation of air baldder occur after hatching. Mathematical model describing the dependence of yolk volume from the time after fertilization indicated that the yolk reserves runs out during the 150th hour after fertilization.By testing different cultivation methods and meat quality of tench, it was demonstrated that low density stocking yilded much better production parameters than high density stocking because of better utility of available foodstuffs. Furthermore, aditional feeding with complete feed mixture lead to favourable meat quality with good fatty acid profile, high protein and low fat.The plan of repopulation of tench into open waters and fish ponds refers to the use of reliable and modern methods in selection of suitable broodstock and their cultivation. Determination of the most suitable localities for the in situ conservation or repopulation/reintroduction after artificial breeding in ex situ conditions is the most important tasks.