[Peculiarities of the biology and parasite fauna of juvenile Atlantic salmon (Salmo salar L.) in the Pista River (White Sea Basin), according to the Gyrodactylus salaris infestation].

Juvenile salmon Salmo salar m. sebago Girard from the Pista River system (the White Sea Basin) was investigated. The data on species composition and occurrence peculiarities of Gyrodactylus salaris Malmberg, 1957 are given. This monogenean is the alien species for the river system and it is recorded for the first time. It is shown that the distribution of the parasite abundance is can be described as the negative binomial distribution; variations of its parameters (k and p) were also characterized. Parasitological data obtained, as well as the data describing the characteristics of growth and age structure of juvenile salmon population, suggest the potential influence of G. salaris infection on the degree of survival of fishes in the lake-river system examined.

[An example of anthropogeneous succession in the ecosystem of the Verkhnetulomsky Water Reservoir (the Tuloma River Basin, the Kola region)].

The destruction of initial biocenoses in the ecosystem of the Verkhnetulomsky Water Reservoir caused deep succession processes. As a result of the loss of the amphipod group in the benthos, replacement of the trophic links in fishes took place in the biocenosis of the reservoir. Benthos feeders changed over to the feeding on zooplankton and, as a result, became the constituent of the predators'diet. The structure of parasitic systems has changed. The parasites using amphipods as intermediate hosts have been and, on the contrary, the abundance of parasites infesting fishes through feeding of the latter on zooplankton has increased. Among the parasites, Triaenophorus crassus Forel became the cause of the appearance of stable triaenophorosis focus.

[Ecological-faunistical review of fish parasites in the Umbozero Lake (the Kola Peninsula)].

Data on fish infestation by parasites in the Umbozero Lake are given. 90 species of parasites were identified including 16 species of Myxosporea, 2 Suctoria, 18 Peritricha, 12 Monogenea, 13 Cestoda, 18 Trematoda, 5 Nematoda, 2 Acanthocephala, 2 Hirudinea, and 2 species of Crustacea. Character of parasites' distribution in fishes of this lake and ecological peculiarities in the host-parasite system are demonstrated.

[Long-term changes in the epizootic of juvenile salmon (Salmo salar L.) in the Keret River (White Sea basin) depending on the invasion of Gyrodactylus salaris Malmberg, 1957].

Results of long-term investigations on the population dynamics of juvenile Atlantic salmon (Salmo salar L.) in the Keret' river (White Sea drainage basin) depending on the invading of Gyrodactylus salaris (Malmberg, 1957) and mass infestation of salmon with this parasite are presented. Gyrodactylus salaris was for the first time recorded in the Keret' river in 1992. During the period lesser than five years the parasite spread along the river. The rise in the infestation of salmon parr with G. salaris caused death of the fish host. As the abundance of juveniles decreased, adult salmon stocks dropped more than 25 times. It was shown, that after the decreasing in number of salmon juveniles following acute epizootic, infestation parameters dropped, and in some years G. salaris was not even found at all.

[Parasite fauna of young landlocked salmon (Salmo salar m. Sebago girard) in the Pista River (the White Sea Basin)].

A native population of landlocked salmon of the Pista River was investigated in 2000-2002. Adult salmon in Pista River has smallest size among other populations of landlocked salmon in Karelia. Data on the biology and parasite fauna of young salmon are presented. The presence of local salmon populations in lakes of the river system is apparently one of the mechanisms keeping the magnitude of population. The presence of Gyrodactylus salaris, a harmful parasite of the young landlocked salmon, is established in this territory for the first time. This monogenean species is believed to have been introduced into the Pista River via stocking from Finland.

[Parasite fauna of the burbot Lota lota L. in body of water of the Kol'skii peninsula].

The results of a parasitological study of the burbot Lota Iota L. inhabiting the Kola region are presented. 51 species of parasite were found on burbot in 16 waterbodies belonging to the White Sea and Barents Sea basins (Muxosporea - 7, Suctoria - 1, Peritricha - 6, Monogenea - 1, Cestoda - 6, Trematoda - 13, Nematoda - 6, Acanthocephala - 5, Hirudinea - 3, Bivalvia - 1 and Crustacea - 2 species). Data on the infestation of burbot by different parasite species and their prevalence in investigated waterbodies were obtained.

[Parasite fauna of the perch fishes Percidae in waterbodies of the Kola Region].

Results of the parasitological investigation of two species of perch fisches (perch Perca fluviatilis and ruff Gymnocephalus cernuus) from Kola Region are given. 63 species of parasites were found on perch in 16 waterbodies belonging to the White Sea and Barents Sea basins (Myxosporea--3, Pleurostomata--1, Suctoria--2, Peritricha--21, Protozoa incertae sedis--1, Monogenea--2, Cestoda--6, Trematoda--10, Nemadota--8, Acanthocephala--4, Hirudinea--1, Bivalvia--1, Crustacea--3). 33 species of parasites were found on ruff in 5 waterbodies belonging to the White Sea basin (Cyrtostomata--1, Hymenostomata--1, Peritricha--8, Monogenea--2, Cestoda--6, Trematoda--9, Nematoda--2, Acanthospehala--2, Bivalvia--1, Crustacea--1). Data on the infestation of perch and ruff by different parasite species are obtained, occurrence of the parasites in the examined waterbodies is shown.

[Seasonal dynamic of the infestation of young landlocked salmon (Salmo salar morpha sebago, Girard) by the monogenean species Gyrodactylus salaris].

Seasonal dymanic of the infestation of young landlocked salmon (Salmo salar morpha sebago, Girard) by the monogenean species Gyrodactylus salaris Malberg, 1957 was studied in the river Lizhma, Karelia. It is established, that the temperature optimal for the development and reproduction of the parasite is about 3-8 degrees C. It is stated, that the abundance of G. salaris in the river Lizhma do not reach so high values, as it was observed in the regions outside the natural area of the parasite.

[Parasite fauna in sticklebacks (Gasterosteidae) from bodies of water of the Kola region].

The results of a parasitological study of the two species of sticklebacks (Pungitius pungitius and Gasterosteus aculeatus) inhabiting the Kola region are presented. The 42 and 14 species of parasite were found in the nine-spined and three-spined stickleback, respectively. The paucity of the parasite fauna in the three-spined stickleback is observed. Distribution of parasites in Kola waterbodies and ecological peculiarities in system "parasite-host" are presented.

[Parasite fauna of the landlocked Atlantic salmon Salmo salar L. in the basin of Namsen river]. / Osobennosti parazitofauny presnovodnogo lososia Salmo salar L. basseina r. Namsen.

The 26 specimens of the landlocked Atlantic salmon Salmo salar L. from Namsen river and its tributary Melingselva river (central Norway) were studied by the method of complete parasitological examination in the period of 1997-1998. The 15 parasite species have been recovered. Ration of parasite with a direct and complex cycle is approximately equal, 6 and 9 respectively. Larval stages of parasites predominate among the parasites with a complex cycle. The parasite fauna fond in the landlocked Atlantic salmon is most similar to that in youngsters of the lake salmon (Salmo salar morpha sebago Girard) and the migrating Atlantic salmon (Salmo salar L.).

[Chloromyxum schurovi sp.n.--new myxosporidian species (Myxosporea: Sphaerosporidae) from salmonid fishes (Salmonidae)]. / Chloromyxum schurovi sp.n.--novyi vid miksosporidii (Myxosporea: Sphaerosporidae) lososevykh ryb (Salmonidae).

New species of the myxosporidian genus Chloromyxum is described from salmonid fishes collected in Karelia, Norway and Finland in 1992-1998.

[Formation of parasite fauna in the bullhead (Cottus gobio L.) (Pisces: Cottidae)]. / Formirovanie parazitofauny obyknovennogo podkamenshchika (Cottus gobio L.) (Pisces: Cottidae).

The formation of parasite fauna in the bullhead Cottus gobio L. in different water bodies was examined. The largest number of parasite species including specific parasites was observed in the Onega and Ladoga lakes. It is suggested that the host and their parasites migrated namely from these water bodies to other part of the range of the bullhead.

[Characteristics of the parasite fauna of the Atlantic salmon fry (Salmo salar L.) in the Teno river system of North Finland]. / Osobennosti parazitofauny molodi Antanticheskogo lososia (Salmo salar L.) rek sistemy reki Teno (severnaia Finliandiia).

The diversity of parasite fauna of the Atlantic salmon parr from the Teno River and its tributaries recovered in 1993-1995 is discribed. 35 parasite species were found, the majority of them are represented by the parasites with a direct cycle of development. High prevalence of infection with Chloromyxum januaricus wes detected.

Effect of naturally occurring visual acuity differences between two eyes in stereoacuity.

Stereoacuity was measured in 30 subjects with a naturally occurring visual acuity (VA) difference between the eyes. The stereoacuity was measured by a modified Howard's apparatus using the staircase method and VA was measured with log MAR charts. Stereoacuity was worse in subjects with a large VA difference between the two eyes; the correlation between stereoacuity and VA difference was significant (r = 0.76, P < 0.001). Neither the VA of the worse eye nor of the better eye contributed to the reduction in stereoacuity. The deterioration was more obvious if VA difference between the two eyes was one line or more (correlation coefficient, r= 0.88, P < 0.001). This study also reinforces the use of a > or = 70% stereothreshold when attempt stereoacuity results to compare with other studies.

[The causes of the formation of an intensive focus of triaenophoriasis in the upper Tuloma River reservoir]. / O prichinakh formirovaniia intensivnogo ochaga trienoforoza v Verkhnetulomskom vodokhranilishche.

Observations on the Triaenophorus crassus invasion in Coregonus lavaretus and Esox lucius were carried out in the period of 1984 to 1989 in the upper Tuloma River [correction of Verkhnetulomsk] water reservoir and Pechozero water body (the Pecha River) which form a common basin. Significant differences were noted in the infection rate of fishes with this parasite in the above water bodies. In Pechozero, where there are preserved natural conditions and therefore an ecological equilibrium in the host-parasite system, T. crassus is not abundant and the infection rate of C. lavaretus and E. lucius with this parasite is low. In the upper Tuloma River [correction of Verkhnetulomsk] water reservoir, due to the dropping out of the amphipod group of benthos from the biocoenosis of the water body, there has been formed a close ecological connection between copepods, C. lavaretus and E. lucius that resulted in the increase of T. crassus and gave rise to Triaenophorus infection of C. lavaretus here.

[The life cycle of myxosporidians in fish of the Kola Peninsula]. / Zhiznennye tsikly nekotorykh miksosporidii ryb Kol'skogo poluostrova.

Monthly studies on the seasonal parasite fauna dynamics of pike, minnow and perch were carried out from May, 1974 to September, 1977. It was found out that the myxosporidian Henneguya creplini has a one-year life cycle. The infection of perch with this parasite takes place at a water temperature not exceeding 13 degrees. In other species (Chloromyxum esocinum, Ch. mitenevi, Myxobolus cybinae) the life cycle is shorter, in consequence of which fishes can be infected with these parasites several times a year and in different seasons. The nature of seasonal changes in abundance of myxosporidians depends to a great extent on weather conditions of each concrete year.

[Effect of hydraulic structures and water storage basins on the parasitic fauna of the Atlantic salmon (Salmo salar)]. / Vliianie gidrosooruzhenii i vodokhranilishch na parazitofaunu atlanticheskoi lososia (Salmo salar).

157 specimens of Salmo salar L. belonging to different age groups were examined in the region of the Lower-Tuloma hydropower-station. 13 species of parasites (of them 5 are freshwater) were found in anadromous migrants. The character of the parasite fauna and the structure of fishes' scale have shown that some salmons cannot get the fishrunning over and stay in summer months under the damb where become infected with freshwater parasites. 19 species of parasites (of them 14 are freshwater) were found in catadromous migrants. These fishes cannot penetrate through the damb of hydroconstruction beyond the limits of the reservoir and pass here to an active feeding that is indicated by a rich composition of freshwater parasite fauna. The infection of adult salmons with plerocercoids of Triaenophorus crassus during the spawning migration points to the presence of trienophorosis nidus in this water reservoir. Parasite fauna of salmon smolt, represented by 7 species, is not affected by the water reservoir and hydroconstruction. The smolt does not stay too long in the reservoir and early stages of its seaward migration do not coincide with the termination of the development of the invasional stages of procercoids of Pseudophylidae.

[Monogenea and fishes of some fresh water reservoirs of the Kol'sk peninsula]. / Monogenei s ryb nekotorykh presnovodnykh vodoemov Kol'skogo poluostrova

25 species of Monogenea were found in the basins of the Ponoi, Pjalitsa and Varzuga rivers. The belonging to faunistic complexes is indicated for 29 species of monogeneans known at present for water bodies of the Kola peninsula. On the basis of the distribution of Monogenea in the Ponoi and due to its hydrological regime and geological past the introduction of freshwater fauna into this water body via the Varzuga river is suggeste.

[Monogenea of fishes from various fresh water ponds of the Kola peninsula].

25 species of Monogenea were found in the basins of the Ponoi, Pjalitsa and Varzuga rivers. The belonging to faunistic complexes is indicated for 29 species of monogeneanus known at present for water bodies of the Kola peninsula. On the basis of the distribution of Monogenea in the Ponoi and due to its hydrological regime and geological past the introduction of freshwater fauna into this water body via the Varzuga river is suggested.