Vol 9, No 2 (2016)

Vendace (Coregonus albula (L.)) is a very plastic species of freshwater whitefish which is widespread in Europe. But in Latvia this species is included into the list of specially protected fish species with limited use. We examined cross-species amplification of 14 microsatellite loci (Cocl-Lav22, Cocl-Lav23, Cisco-59, Cisco-106, Cisco-90, Cisco-126, Cisco-157, Cisco-179, Cisco-181, Cisco-183, Cisco-200, BWF1, BWF2, and C4-157) which were successfully used for genetic studies, monitoring, protection and management of different Coregonus species. Five microsatellite markers (BWF1, Cisco90, Cisco126, Cisco157, Cisco 200) had a good representation in populations of vendace from seven Latvian lakes (Sventes, Rāznas, Nirzas, Dridzas, Stirnu, Aluksnes, Ežezers) and were used for genetic analysis of these populations. The mean number of alleles per locus (from 4.4 to 6.2), the observed (from 0.53 to 0.70) and expected (from 0.49 to 0.70) heterozygosity, population structure (F_ST and R_ST) and gene flow (Nm) were also analysed in Latvian vendace populations.

Coregonus peled (Gmelin) (Teleostei: Salmoniformes: Coregonidae), which is considered an important object of coldwater aquaculture, had been successfully introduced into an enclosed Western Mongolian lake Ulaagchny Khar in the early 1980s. At the same time larvae of two other Coregonus species—Baikal omul C. migratorius (Georgi) and least cisco C. sardinella Valenciennes—had also been released into the lake. Baikal omul was then reported as a naturalized species. This might have caused interspecific hybridization and gene introgression. Identification of coregonids by morphology can be problematic, so to determine which species was dominant in the lake (we presumed it was peled) and if its gene pool was affected by other introduced Coregonus species we sampled 40 individuals and analyzed them by sequencing a fragment of mtDNA cyt b and by allozyme electrophoresis. The analysis showed that all the fish belonged to C. peled with no evidence of admixture from other coregonid species. Taking into account mass release of both species in 1980s, it is evident that naturalization of peled in the lake was much more successful than that of Baikal omul.

The content of total lipids, total phospholipids, and fatty acids of total lipids in muscles and liver of juvenile Lake Baikal sympatric coregonid fishes have been analyzed for the first time under a common garden experiment. Baikal omul, Coregonus migratorius Georgi, is an active migrant of the pelagic zones of the lake. Baikal (lacustrine) whitefish, C. baicalensis Dybowski, is a colonizer of the bottom habitats, which are relevant to the pelagic zones of the littoral and underwater slope. Structural lipids (phospholipids and cholesterol) dominated in total lipids of the tissues of all fish under study. Spare lipids significantly prevailed in omul muscles when compared to whitefish. The highest variability of fatty acid composition was reported in muscles of coregonid fishes. Statistically significant differences were revealed in the content of the ω3 polyunsaturated fatty acids in muscles of lacustrine whitefish and omul. Associations of lipid compositions revealed in tissues of the whitefishes under the study with their respective ecotypes have been discussed.

The correlation between the energy and carbohydrate metabolism rate with the length and weight of salmon (Salmo salar L.) and whitefish (Coregonus lavaretus L., Coregonus albula L.) studied in nature and farmed rainbow trout (Parasalmo mykiss Walb.) has been investigated. The results of the study show that the largest and fastest growing fish had high activity of enzymes involved in aerobic energy metabolism (cytochrome c oxidase and malate dehydrogenase) and anaerobic metabolism (lactate dehydrogenase in muscles and 1-glycerophosphate dehydrogenase and glucose-6-phosphate dehydrogenase in liver). Age-related changes of the investigated parameters are caused by a general reduction of the aerobic metabolism rate and oxygen consumption during ontogenesis, increased lipid metabolism, and the amount of stored substances. It is also shown that pubescent male and female whitefish (4+ and 5+) have differences in the correlation between enzyme activity of cytochrome c oxidase, 1-glycerophosphate and glucose-6-phosphate dehydrogenases and the length and weight of individuals.

Structure and cytometric indices of red blood cells (RBC) and hemoglobin content (Hb) and oxygen capacity of the blood (OCB) of omul, whitefish, and hybrids thereof captured in Lake Baikal (wild) and incubated and grown in a freshwater aquarium complex (FAC) (farmed) have been analyzed. Cytometric parameters of red blood cells of wild omul, whitefish, and hybrids thereof exceed those of the cells of fish reared in aquariums under identical conditions. The effect of aquarium rearing on the shape of red blood cells is the least pronounced in Siberian whitefish and F1 progeny of Siberian whitefish females and omul males (f Sw x m Om). The erythrocyte size in hybrids of female Lacustrine whitefish and male omul (f Lw x m Om) is determined by the size of these cells in female parents, since female Lacustrine whitefish have the largest erythrocytes. Cytometric parameters of erythrocytes of all Coregonid fishes investigated are higher in fish reared in warm aquaria than in conspecifics reared in aquaria with cold water. Erythrocyte nuclei are smaller in artificially propagated hybrids than in parent fish captured in the wild or in whitefish and omul reared in aquaria under the same conditions. A distinct pool of erythrocytes from whitefish captured in the wild have a 20–30% higher content of functionally active mitochondria than erythrocytes of whitefish reared in aquaria; a disrupted mitochondrial structure is also observed in erythrocytes from the latter population of fish. The results show that distinctive features of metabolism related to oxygen transport in the Baikal coregonid fish that were investigated are determined by adaptation to the conditions of the ecological niches occupied by the fish.