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  • 1990-1994  (5)
  • 1985-1989  (4)
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Materialart
Erscheinungszeitraum
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Schlagwörter
  • 1
    Digitale Medien
    Digitale Medien
    The ecology of brown trout Salmo trutta in English chalk streams (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 21 (1989), S. 0 
    Details
    ISSN: 1365-2427
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: SUMMARY. .1. Chalkstream trout are fast-growing, short-lived with a stable age structure that is a consequence of the lack of extremes in the abiotic environment, especially of water temperature and flow.2. Levels of secondary (invertebrate) production arc high and there is no evidence that interspecific or intraspecific competition for food resources limits growth.3. Dietary studies show a broad similarity between trout and other species, but indicate differences that reflect variations in the micro-habitat distributions between fish species.4. Trout numbers appear to be limited initially by the availability of gravel spawning areas, and then by areas suitable for newly-emerged fry. Reduction in stream discharge in the spring, either naturally or by man, can lower the number of 0+ trout that survive.5. Eels are not important predators on trout eggs or fry. but a reduction in pike numbers can lead to a decrease in the mean weight of pike. Small pike do not pose a serious threat to stocked yearling trout.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2427.1989.tb01348.x
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  • 2
    Digitale Medien
    Digitale Medien
    Fast- and slow-growing pike, Esox lucius L., and problems of age-determinations from scales (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 21 (1990), S. 0 
    Details
    ISSN: 1365-2109
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract. River Frome pike, Esox lucius L., usually spawned in drainage channels connected to the main river. Most 0+ pike moved into the river during their first summer, but some remained in the channels until the following year. The latter group ate macro-invertebrates (chiefly Asellus), whereas their siblings in the main river were piscivorous. 0+ pike in the channels had slower growth rates than those in the river, but growth rates of the two groups in later years were similar. The presence of these initially slow-growing pike in the population caused problems in identifying the first annulus on the scales. The problem was identified by batch-marking 0+ fish in different years and examining scales from individuals that were subsequently recaptured. The interpretation of true annuli and false checks in older fish was aided by collecting sets of scales from individually tagged pike which were recaptured at intervals over a number of years. The study emphasized the importance of validating age determinations by obtaining information from more than one source.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1365-2109.1990.tb00485.x
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  • 3
    Digitale Medien
    Digitale Medien
    On the accuracy of age-determination using scales from rudd, Scardinius erythrophthalmus (L.), of known age (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 26 (1985), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Six scientists from five European countries each examined 29 sets of scales from rudd of known age. The material contained 174 scales from both fast and slow growing fish and, with the exception of one participant, the scientists missed the first annulus when it was formed close to the scale centre. Sixty-eight scales were misread in this way, but only 12 were incorrectly aged because of confusion between true and false annuli. Comparisons of back-calculated lengths with observed lengths at each age were used to identify which false annuli had been incorrectly identified as true annuli, and vice-versa. The results confirmed the necessity of having information from other sources, e.g. seasonal length-frequency distributions of 0-group fish, to support the subjective interpretation of the scales.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1985.tb04302.x
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  • 4
    Digitale Medien
    Digitale Medien
    Effects of impoundment on populations of bullhead Cottus gobio L. and minnow, Phoxinus phoxinus (L.), in the basin of Cow Green Reservoir (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 38 (1991), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The distribution, growth and reproduction of bullhead, Cottus gobio, L., and minnow, Phoxinus phoxinus (L.), were studied at Cow Green Reservoir, Upper Teesdale, for 10 years following impoundment in 1970. Comparisons were made with pre-impoundment results. The length-for-age of bullheads increased after impoundment. The length-for-age of minnows decreased. In winter both species were confined mainly to deep water or to the stone facing of the earth dam. In summer they were found throughout the reservoir though bullheads were scarce in the littoral zone. Female bullheads became sexually mature at an earlier age (84% at age-group I) than before impoundment (33% at age-group I) but no change was apparent amongst males (67–62% in age-group I). The post-impoundment sex ratio did not differ from 1:1 and individual fecundity did not change after impoundment. There was a significant reduction in individual fecundity of the minnow. The mean instantaneous rate of mortality (Z) for bullhead of age-groups II to IV was 0.96 ± 0.34 year−1, compared with 0.85 ± 0.29 year in the Tees before impoundment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1991.tb03161.x
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  • 5
    Digitale Medien
    Digitale Medien
    Environmentally-induced fluctuations in year-class strength and their implications for management (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 27 (1985), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Data for river populations of common freshwater species including dace, chub, roach, gudgeon and pike are examined to assess the magnitude of natural density-independent fluctuations in the strength of year-classes. Both in the cyprinid populations and in those of some salmonids, only occasional years give rise to large cohorts of adult fish. Correlations with temperature indicate that for the cyprinid populations these are often years when temperatures are high. In the River Frome, Dorset there is a significant relationship between the growth of O-group dace and subsequent year-class strength. Faster-growing larvae may be better able to avoid predation. Both the habitat and feeding requirements of these young fish are different from those of the adults. A practical approach to improving recruitment in a population of a given species would be to first characterize, and then increase, the availability of suitable habitats and food organisms for the larval stages.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1985.tb03243.x
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  • 6
    Digitale Medien
    Digitale Medien
    A pike management strategy for a trout fishery (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 27 (1985), S. 0 
    Details
    ISSN: 1095-8649
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: The efficiency of pike removal from a chalkstream trout fishery, by an angling society using electrofishing, was estimated over five successive autumns using mark-recapture methods. It averaged c. 50% for pike aged 1+ years or more. Numbers of 3+ and older pike decreased from 3.7 ha-1 (1980) to 1.4 ha-1 (1984), but there was no corresponding reduction in recruitment success. Both pike immigration and an inverse relationship between natural and fishing mortality could have reduced the effect of the pike culls. The mean weight of 0+ pike increased from 19.4 g to 48.2 g over the 5 years, but there was no change in the growth rates of older pike. Only the larger pike were able to eat the larger trout stocked, and the reduction in numbers of 3 + and older pike appears to have reduced the predation pressure on the trout population. Angling effort increased more than three-fold over the 5 years studied and rod-catches more than doubled, but catch-per-unit-effort was extremely variable between years. The increased rod catch occurred despite the decrease in numbers of large (〉 33 cm) trout stocked in the spring and early summer. Compared with pre-cull years, the angling society saved about ş850 (present day prices) by stocking fewer trout.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1095-8649.1985.tb03244.x
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  • 7
    Digitale Medien
    Digitale Medien
    Comparative growth and diet of tench Tinca tinca (L.) larvae and juveniles from river floodplain biotopes in France and England (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Ecology of freshwater fish 2 (1993), S. 0 
    Details
    ISSN: 1600-0633
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: The growth and diet of larvae and 0 + juveniles of riverine tench Tinca tinca (L.) were compared in two stagnant floodplain biotopes from the upper River Rhône, France, and the River Great Ouse, England. The diet of tench was generally similar at the French and English sites, with Cladocera being the predominant prey of young larvae (English site only). Cladocera and Copepoda were the principal prey of older larvae and 0 + juveniles, though the latter took a variety of other, larger prey items. Ontogenetic changes in diet at both sites probably reflect prey availability. Protracted spawning at the French site contrasted a single spawning effort in the English backwater. Fluctuations in growth rate and condition were observed to coincide with shifts in diet, suggesting that tench developing in riverine biotopes may be vulnerable to competition at particular transitional intervals in their early ontogeny.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1600-0633.1993.tb00084.x
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  • 8
    Digitale Medien
    Digitale Medien
    The biology of the eel Anguilla anguilla (L.) in an English chalk stream and interactions with juvenile trout Salmo trutta L. and salmon Salmo salar L. (1991)
    Springer
    Hydrobiologia 218 (1991), S. 65-76 
    Details
    ISSN: 1573-5117
    Schlagwort(e): eels ; salmonidae ; competition ; chalk streams
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The age, growth, annual production and diet of the eel Anguilla anguilla were examined in a chalk stream in southern England. Growth in length fitted the von Bertalanffy model: L t = 708(1 − exp( − 0.064(t + 0.625))), where L t is the mean length (mm) at age t years. Annual length increments over the first 10 years averaged 31 mm, and annual production was 3.43 g m−2 y−1 (range 3.13–3.75). This fell to 2.09 (1.75–2.34) over two years as result of successive eel culls. Comparisons of eel diets with those of juvenile salmon Salmo salar and trout S. trutta showed that eels preyed more on benthic invertebrates, whereas the salmonids took more mid-water and surface prey. Piscivory was most marked in eels 〉400 mm, but few salmonids were eaten; most fish prey were the sculpin Cottus gobio. Attempts to reduce the eel population by successive eel culls were only partly successful because of the upstream immigration of elvers and downstream migration of silver eels into the study area. We conclude that, in this salmonid nursery stream, eels do not have a measurable effect on the salmonid population through predation or by utilizing the same food source.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00006419
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  • 9
    Digitale Medien
    Digitale Medien
    Production of juvenile Atlantic salmon,Salmo salar, in natural waters (1994)
    Springer
    Reviews in fish biology and fisheries 4 (1994), S. 262-263 
    Details
    ISSN: 1573-5184
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00044134
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