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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 46 (1995), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Data are presented from a 10-year (1984 to 1993) study of a Salmo trutta population in the Afon Cwm, a small tributary of the Afon Dyfi, mid-Wales. The stream is a spawning and nursery area for sea trout. Growth of trout within the stream can be summarized by a von Bertalanffy growth coefficient (K) of 0·310, with asymptotic length (1∞) 21·6 cm and with length at age 1 of 7·6 cm. Mean population density in the whole stream varied from year to year between 0·05 and 0·60 0-group trout m−2 and between 0·05 and 0·70 older trout m−2. Mean biomass varied, between years, from 0·1 to 3·5 g m−2 for 0-group and from 1·3 to 10·4g m−2 for older trout. Loss between 3 and 5 months of age appeared to be proportionate at about 50 to 60% and instantaneous loss rate from 5 to 53 months of age varied from 0·04 to 0·10 month−1 and was positively correlated with cohort number at 3 months of age. Production between 3 and 53 months of age varied between cohorts from 3 to 8 g m −2 live weight.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 21 (1989), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 17 (1986), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. The Freshwater Biological Association has operated a salmon counter on the River From, Dorset. England since 1970. In this calcareous river, false upstream counts generated by mats of aquatic macrophytes floating downstream have proved the main constraint to the accuracy of the installation. In addition, time-delays in the counter logic circuitry prevent the use of still photography to check the identity of downstream records. This paper gives a full description of the technical details and basic program listings for an inexpensive microcomputer-based system to record the out-of-balance voltage signals from the resistivity counter. Comparison with still photographs indicates that the totals recorded can be corrected on the basis of differences in the form of signals generated by salmon and by other objects, including weed-mats. The fast response time of the microcomputer-system made it passible to confirm that most objects which generated downstream counts on Ihe River Frome resistivity counter were either salmonids or eels.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 21 (1990), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 11 (1980), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A simplified Seaburg sampler was used to obtain stomach contents from anaesthetized pike. Well-digested remains of fish prey were identified from pharyngeal bones (Cyprinidae) or the skeletal structure of the caudal region, by comparison with type material collected from fresh fish. The original lengths of the prey were estimated from linear relationships between fish length and size of the caudal fin, or size of the pharyngeal bone. Estimation of prey size from scales or otoliths using length-for-age data gave only approximate values.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 25 (1984), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Otoliths from 640 flounders from the River Frome, a chalk river in southern England, were used for age and growth studies together with length-frequency data. Mean lengths at ages I–V were 89, 151, 225, 304 and 323 mm respectively; these are higher than have been reported for marine populations. All flounders caught were immature and, on reaching the sea, both sexes probably became sexually mature a year older than did the marine populations. Flounder diets in freshwater comprised largely aquatic insects, Mollusca and Crustacea but there were differences between large and small fish; seasonal changes in diet largely reflected prey availability. It is suggested that competition for food and space in estuaries between 0 group flounders have given rise to the migration into fresh water.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A novel cross river, self cleansing system for the remote monitoring of downstream and upstream migration of PIT tagged fishes past a fixed point in deep, fast flowing rivers is described.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 21 (1982), S. 0 
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: A first report and description is given of the formation of‘mirror’ scales on dace, Leuciscus leuciscus (L.), Cyprinidae; a similar scale formation in carp, Cyprinus carpio, Cyprinidae is often associated with decreased growth rate, but this was not observed in the dace.
    Type of Medium: Electronic Resource
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