| Abstract [eng] |
SUMMARY Distribution, biology, population and genetic patterns of brown trout (Salmo trutta fario L.) in Lithuanian evaluated on this master thesis. Data were collected during 2002-2005 years in 15 rivers in the Neris, Sventoji, Venta, Zeimena and Merkys river basins. There are more than 180 rivers where lively populations of brown trout are found in Lithuanian. Those rivers comply with Salmon rivers requirements and have favourable characteristics for salmonidae fishes: low average annual water temperature (<+12oC); fine oxygen regime all-year round (disolved oxygen amount > 7 mg/l); low level eutrophication and flow exceeding 0,3 m/s. 32 species of fishes and cyclostomata subject to 7 orders and 12 families were found in the investigated rivers. Majority of species (16) belongs to Cyprinidae family. Brown trout, bullhead, stone loach, minnow and dace were most abundant constant species and form core in fish communities in investigated rivers. Mean annual density of brown trout was 8,57 ind./100m2 and varied from 6,00 to 10,54 ind/100m2 , mean biomass was 313,35 g/100m2 and varied in 251,04-359,06 g/100m2 range. 0+ and 1+ age brown trout were most abundant among all age groups (take 51,30 and 34,03% part on population), biomass dominant age groups were 1+ and 2+ (38,27 and 29,15 %). Maximum pace or growth observed on first year living. 0+ age group trout reached 9,12 cm of length (L) and 7,9 g weight (Q, g); 1+ - 16,77 cm length and 50,1 g weight. Pace of growth depends on climatic conditions, intraspecific and interspecific competition. Differences on pace of growth and density on different age groups in climatic regions of Lithuania can be explained by intrapecific and interspecific competition. Fastest growth rate of young age group (0+ and 1+) brown trout was observed in Southeast region, where species richness were poorest, slowest growth rate observed on Middle and Zemaiciai region, where species richness were best. There were given observation about brown trout diet. Estimated that main part of 0+ age group brown trout diet consist of Chironomids; for 1+ trout age group – spineless complex (Ephemeroptera-Plecoptera-Tricoptera-Diptera); come age trout become real predators and prefer large prey (fish fry, large invertebrates). Study of brown trout genetic pattern in Lithuania rivers were based on mtDNA polymorphism. There 4 haplotips was found: AAAAA (0,4 - density in population), ABCAB (0,4); BACAA (0,13) and BADAA (0,07). Comparison between Sea trout and Brown trout reveal fact that the same haplotips dominate, but density of it in populations differs. |
