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  • 1
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Science Ltd
    Journal of fish biology 62 (2003), S. 0 
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Radio tagged common carp Cyprinus carpio in a Namibian reservoir, where this species has been introduced, experienced 100% mortality or tag loss ( n = 13) with surgically implanted transmitters and 100% survival ( n = 5) with externally attached transmitters at water temperatures of 24–25° C. It seems that the negative effects of the tagging were greater for surgical implantation than for external attachment. The body shape of common carp make them well suited for external tagging, and this tagging method is recommended for common carp studies at high water temperatures or under other stressful conditions.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 60 (2002), S. 0 
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Within smolt ages there was a strong negative correlation between pre- and post-smolt growth in wild three-sea-winter female Atlantic salmon Salmo salar. This indicates that trait values providing, or resulting from, increased growth in one environment may cause growth to decrease in the other, potentially constraining growth rate evolution.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 19 (1988), S. 0 
    ISSN: 1365-2109
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract. In this study we aged eels, Anguilla anguilla (L.), from a pond in the Netherlands stocked with elvers in 1966. Yellow eels were sampled from the pond in 1981. Burning and cracking the otoliths of these eels gave the expected age (15 years) in 27% of the cases, with a mean estimated age of 12·3 years. As some immigration of young eels into the pond must have occurred after stocking, the percentage of correctly determined specimens is even higher. Clearing the otoliths in ethanol was not a good method for these eels, giving a mean estimated age of 7·7 years and no age over 10 years. The use of the burning and cracking technique is recommended.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 33 (1988), S. 0 
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Oxford, UK; Malden, USA : Blackwell Science Ltd
    Journal of fish biology 65 (2004), S. 0 
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Thirty Atlantic salmon Salmo salar parr (mean 135 mm total length, LT) in the River Alta, Norway, were radio-tagged and tracked during a 11–13 day period. The parr stayed within defined home ranges with a 95% probability of localization within an average area of 1286 m2(241–3484 m2). On average, each parr had overlapping home ranges with 7·7 other parr, and the overlap between pairs of fish covered on average 24% of their home range areas. Mean length of the river stretch used was 90 m (22–383 m). On average, during 38%(16–77%) of the tracking surveys, the fish had moved 〉10 m since the previous survey. Mean total distance moved during the whole study was 402 m (208–862 m). The Atlantic salmon were most often recorded in riffles, but 27% of the parr alternated between riffles and pools. The extensive movements, flexible habitat utilization and relatively large home ranges, together with the fact that all the parr had home ranges partly overlapping with other radio-tagged parr, indicate a flexible and variable behaviour and, thereby, a more complex social structure than a rigid defence of a fixed territory. Thus, Atlantic salmon production seems not to be limited by the highest potential number of territories for large parr in a given area.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 38 (1991), S. 0 
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The vendace Coregonus albula (L.) populations in the lakes Mjøsa and Osensjøen exhibited fluctuating year-class strength. In Mjøsa, a strong year-class emerged every third year, except for the four year period between the strong year-classes 1969 and 1973. The difference between the strong and weak year-classes decreased from the 1960s, through the 1970s to the 1980s. The Mjøsa vendace matured sexually at age 2 +, and more than ten sexually mature age-groups were present in the population. Growth ceased at maturation, and asymptotic length was 23.6 cm. In Osensjøen, one strong year-class (1969) dominated the population during the period 1976–1987. The Osensjøen vendace matured sexually at age 3, and more than 15 sexually mature age-groups were present in the population. Growth ceased at maturation, and asymptotic length was 28.4 cm. In both lakes, vendace fed on crustacean zooplankton in the epilimnion throughout summer and autumn. Our data indicate that regular year-class oscillations occur as a result of the juvenile survival being negatively correlated to the number of adults.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 30 (1987), S. 0 
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Pennate diatoms, especially Aslerionella spp. and Tabellaria fenestrata, were the most important food items for smelts in Lake Mjøsa during the first month of external feeding; rotifers and early stages of copepods were eaten occasionally. Later, during summer and autumn, crustacean zooplankton (cladocerans and copepods) were the most important food items; selected species were Polyphemus pediculus, Eudiaptomus gracilis, Limnocalanus macrurus, Heterocope appendiculata. Leplodora kindti, and Bythotrephes longimanus; some smelts larger than 7.4 cm fed on Mysis relicta. In 1979 and 1980, mean lengths of smelts in October-November were 4.7 cm and 7.2 cm, respectively. A difference in length increment between the two years may have resulted from summer water temperatures being higher in 1980 than in 1979.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Administration of thyroxine to hatchery-reared Atlantic salmon smolts raised blood serum thyroxine levels 24 h later to exceed those in controls. Treatment also slowed downstream movement when smolts were released into a stream above a fish trap. The descent of smolts released immediately after being challenged with high-water flows for several hours was also slowed, and proportionately fewer challenged fish than controls were captured at the fish trap. These findings were consistent in each of two years. Only in one year, however, could flow-challenge be shown to raise endogenous thyroxine levels in blood serum. It is concluded that exogenous thyroxine treatment and flow-challenge before release have qualitatively similar effects on downstream movement but that this similarity is possibly not a consequence of the common effect of increased serum thyroxine raised either exogenously or from the thyroid system itself.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 55 (1999), S. 0 
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Brown trout in Lake Femund migrated from the nursery streams mainly at 2 years old, but ranging between 1 and 8 years. Brown trout switched to piscivory from 3 years onwards, and a body length of 17·5 cm, according to back calculation from scales. Fast growers switched to piscivory at a younger age and smaller size than slow growers. The most slow-growing trout switched to fish feeding at 9 years old and a mean body length of 36 cm. The growth of the invertebrate feeders was almost rectilinear to c. 45 cm and 11 years of age. Switching to a fish diet induced increased growth rates. Age at sexual maturity increased with the age at which the fish became piscivorous. The invertebrate feeders matured at an age similar to that of the most fast growing piscivorous trout. The mortality rate of sub-adults and adults did not differ significantly between fish and invertebrate feeding trout. Longevity of piscivorous trout was estimated at 11 years and of invertebrate feeders at 10 years.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Oxford, UK : Munksgaard International Publishers
    Ecology of freshwater fish 14 (2005), S. 0 
    ISSN: 1600-0633
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract – During 6 November to 24 December 2000, 23 tigerfish [(Hydrocynus vittatus), 30–54 cm] were tagged with radio transmitters in the Zambezi River (Namibia) to record habitat utilisation during low, rising and high water levels. The fish were tracked, on average, every fourth day during 23 November to 18 May. Two movement patterns were detected. Approximately 50% of the fish moved 〈1000 m among tracking surveys, staying within ‘defined’ home ranges. The remaining fish showed consistent site fidelity for periods, with long distance movements (〉1000 m) to new areas among residency periods. Overall, mean distance moved between tracking surveys was 1447 m. Home range size varied among individuals, with a 95% probability of localisation within an average area of 276,978 m2. The fish utilised a mean river stretch of 18,836 m (range = 90–71,840). All the fish were recorded in the main stem, and on average, 95% of the fixes were in the main stem during low water. However, the fish used temporary flooded areas to an increasing extent during the rising and high water period, but did not undertake long-distance migrations into the floodplains. Fish were sometimes near vegetation, but were never recorded into or under vegetation.
    Materialart: Digitale Medien
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