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Four cranial bones (supraethmoid, glossohyal, premaxilla, vomer) of nine-month-old reciprocal hybrids of Salmo salar and Salmo trutta and the arrangement of the opercular bones in reciprocal hybrids aged from 4 to 24 months were analyzed. The supraethmoid bone in the majority of the hybrids studied was similar to that of salmon. In some hybrids, an atypical additional process was found on the lower part of the supraethmoid bone. The large process of the premaxilla bone had a short base in the two groups of hybrids as in salmon, and it was low as in trout. The shape of the vomer plate was intermediate between a triangle (as in trout) and a pentagon (as in salmon) in the majority of salmon x trout hybrids and almost half of the trout x salmon hybrids. The glossohyal in some hybrids had an uneven number of teeth in each row, and these rows of teeth were uneven.
The last remaining salmon population in Poland went extinct in the mid 1980s. The salmon restoration program in Poland in based on Daugava salmon, and the first eyed Daugava salmon eggs were imported to Poland in 1985, and they continued to be imported in subsequent years. Spawners were reared in net cages in the Gulf of Gdańsk. Salmon smolts have been released into Pomeranian rivers and the Vistula River since 1994. Between 1994 and 1999, 1, 644, 936 salmon smolts were released, of which 63, 602 were tagged. Overall, there was a low recovery rate of tagged specimens, and from many experiments there were no recoveries at all. The highest recovery rate was 4.5%. Tagged salmon migrated throughout the Baltic Sea, but the highest concentration of catches were in the Gulf of Gdańsk, near Bornholm and in the Gulf of Finland. In the first winter, the tagged salmon attained an average length of 62.9 cm and an average weight of 2.9 kg, in the second winter theses figures were 76.1 cm and 5.3 kg, and in the third they were 90.7 cm and 7.6 kg.
Background. Early maturation of salmon males (Salmo salar L.) affects the reduction of fish physical condition and culture Materials and Methods. Atotal of 145 salmon males belonging to a group of low growth rate specimens that had not smoltified during the first spawning season were sampled from the "Aquamar" Fish Farm (Miastko, Poland). The study was based on light microscopy examination of histological sections and a standard procedure of milt quality evaluation. The gonadal development stage was determined with Billard and Escaffre ′s 9-grade scale modified by Dziewulska. Results. The mean fork length of males was 10.45 cm. Three groups of males were distinguished: non-maturing (stage I); beginning spermatogenesis (inactive substage II); and precocious (stages VI to IX plus maturing males classified as undergoing "attempted spermatogenesis"). The groups contained 72.4, 4.8, and 22.8% of the males examined, respectively. The gonadosomatic index recorded in the three respective groups ranged from 0.010 to 0.164 (mean 0.040); 0.050 -0.155 (0.089); and 0.058 -6.219 (1.358). The gonadosomatic index is not an accurate indicator of gonadal activity. The precocious males semen contained from 6.1 to 23.0 million spermatozoa per mm 3 (13.41 million on the average). Spermatozoa performing progressive movements constituted 80-90%. Results. On the other hand, precocious male can fertilize mature eggs. The aim of this study was to estimate the magnitude of precocious maturation and to evaluate semen characteristics in a group of cultured 1-year-old salmon. Conclusion. Among non-maturing males and males beginning spermatogenesis, precocious individuals were detected, the latter produced semen of good quality.
Background. The effect of the magnetic field on fish egg shells has not attracted major interest of researchers, even though it could have been predicted that such effect may be vital to fish embryogenesis. One of the hitherto-neglected aspects of the magnetic field action of fish eggs are the changes in the egg shell permeability and possible alteration of the process of embryogenesis. Studying this process and learning the associated phenomena may be important in explaining cases of substantial mortality of the embryos. Materials and Methods. Fish eggs (Atlantic salmon, Salmo salar L.; sea trout, Salmo trutta L.; and rainbow trout, Oncorhynchus mykiss (Walbaum, 1792) and isolated egg shells, in a custom-made osmometer setups, were subjected to the action of a stable magnetic field (2 mT). The ultrastructure of the egg-shells was studied using a scanning electron microscope (JEOL JSM 6100). Results. Stable magnetic field (2 mT), affecting fish eggs, caused statistically significant increase in the egg-shell permeability to water, in the period of the egg activation (and also less distinct increase during the entire embryogenesis). Conclusion. Weak, stable magnetic field increases egg-shell permeability to water affecting water management processes in fish eggs, during incubation. This phenomenon may have practical implications for fish hatcheries
Background. Arctic charr, Salvelinus alpinus (L.), are known to harbour significantly more sea lice, Caligus elongatus von Nordmann, 1832, than do Atlantic salmon, Salmo salar L. This research investigated whether this is due to differences in initial infection or to resettlement/loss of mobile adults. Skin mucus protein profiles and epidermal histology were also studied as two characteristics that might help explain interspecific differences in host susceptibility. Materials and Methods. Atlantic salmon and Arctic charr were sampled from the sea-pen after 12 weeks of exposure to natural infection. Fishes were examined for sea lice counts and mucus was analysed for protein profiles using standard methods of poly-acrylamide gel electrophoresis. Epidermal tissue of fishes around chalimus attachment sites was also examined by transmission electron microscopy. Results. Interspecific differences in host susceptibility were determined not to be due to differences in initial infection rate, as charr and salmon had similar numbers of attached chalimi. Adult parasites were significantly more numerous on charr as a result of resettlement of adults lost by other fishes in the area. Gel electrophoresis indicated that salmon had a greater abundance of skin mucus proteins than charr, particularly in the 30–42 and 67–94 kDa range. Ultrastructural analysis of epidermal tissue indicated that charr had more mucous cells and showed evidence of possible osmotic stress. Interspecific differences also existed in intercellular adhesion characteristics. Salmon and charr showed a similar absence of inflammation around chalimus attachment sites. Conclusion. Artic charr had a more intense infection with Caligus elongatus than did salmon corresponding to fewer potentially antagonistic proteins in the mucus. Perhaps also, the epidermis of charr provides more easily accessible food for the sea lice. Higher levels of stress in charr in sea water may also have predisposed them to higher sea lice infections.
Deteriorating environmental conditions and overexploitation in situations of insufficient fish stocking or a complete lack of it led to the extinction of salmon in Polish waters. The last population of salmon in the Drawa River disappeared in the mid-1980s. The aim of this work was to re-establish salmon in Polish waters. The salmon for this purpose came from the Daugava River, when in 1985 and 1987, 50 000 and 30 000, eyed salmon eggs were bought, respectively. Up to 1996, salmon spawners were in the floating reared net cages in of the Puck Bay. Since 1994, spawns of salmon have been reared in freshwater at the fish farm "Aquamar" at Miastko. Stocking of smolt started in 1994 and by the year 2001, 2 238 653 one- and two-year-old smolts had been released. Smolts were released into rivers in the Pomeranian region, the Drawa, and the Vistula and its tributaries. Between 1994 and 2000, 77912 one- and two-year-old tagged smolts were released together with untagged ones. The first salmon in the Vistula and Drwęca rivers were noted in 1996. From 1997 to 2000, salmon catches in rivers fluctuated between 413 and 9714 kg. From 1997 salmon spawners were captured for artificial spawning. The largest spawners were 120-cm long and weighed 17.5 kg. Alongside untagged spawners, single tagged salmon were also used for spawning purposes. In 1997, a total of 382 000 eggs were obtained. In later years the number of spawns obtained grew, and in 2000 the number of eggs collected was 2 260 000. In 1996, spawns from salmon raised in pools at Świerzenko were collected. In 2000, there were 1168 females (length 30 - 70 cm) from which 9 300 000 eggs were collected. From 1997, large nests were observed at the spawning grounds in the Drawa River. In next years salmon nests were observed in the Drawa River and also in Parsęta and Wieprza rivers. Percentages of recovers from tagged salmon were very low and varied from zero to 7.35. Tagged salmon migrated all over the Baltic Sea. The most often they were caught in the Gulf of Gdańskarea, near Bornholm Island and in the western part of the Gulf of Finland. Salmon entered rivers mainly into Vistula, Drwęca and Wieprza rivers for spawning purposes. Some spawners strayed and entered rivers to which they were not released as smolt. Higher percentage of homing were observed among smolt into Vistula i Drwęca rivers than among smolt released into Pomeranian rivers. Tagged salmon after the firs year reached average length of 59.4 cm and average weight of 2583 g, after the second year 81.8 and 6255 g, after the third year 102.4 cm and 11800 g respectively.
The authors investigated the carotenoids content in yellow, yellow-orange, and orange eggs of salmon (Salmo salar L.) and brown trout (Salmo trutta L.) entering Polish rivers for spawning or reared in fresh water. The study shows the presence of females of both salmon and brown trout with the M74 syndrome.
Ryby stanowią istotne źródło składników odżywczych, w tym witamin z grupy B. W niniejszej pracy oznaczano stężenie witamin B6 i cyjanokobalaminy w częściach łososi norweskich i bałtyckich pochodzących z rynku metodą wysokosprawnej chromatografii cieczowej (HPLC). W badaniach stwierdzono istotne korelacje (p<0,05; p<0,01; p<0,001) zawartości witamin B6 i B12 (cyjanokobalaminy) w badanych częściach łososi norweskich i bałtyckich.
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