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  • 1
    Electronic Resource
    Electronic Resource
    Individual variation in progeny size and quality in rainbow trout, Oncorhynchus mykiss (Walbaum) (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 27 (1996), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Early life history traits of fish are very variable as a result of both genetic and environmental factors. In this study, we examine individual variation in early life history traits in progeny of seven females crossed with one male rainbow trout, Oncorhynchus mykiss (Walbaum). Individual eggs were followed from fertilization through hatching until death of the larvae by starvation. Larvae and yolksac size (size was shown to be a good indicator of energy content) increased with increasing egg size, but there were still differences between families after variation in egg size was accounted for. Incubation time was not correlated with egg size, and did not differ between families. The progeny from the different families utilized the available energy differently, as both longevity and growth-rate without food was independent of yolk-sac size, but strongly dependent on family. The observed between-family differences in early life history traits in rainbow trout were mainly caused by genetically based effects; egg size and thus probably egg quality, which differed strongly bet ween females, could not adequately explain these differences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2109.1996.tb01260.x
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  • 2
    Electronic Resource
    Electronic Resource
    Reading otoliths of eels, Anguilla anguilla (L.), of known age from Kolderveen, The Netherlands (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 19 (1988), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2109.1988.tb00588.x
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  • 3
    Electronic Resource
    Electronic Resource
    Temperature-dependent activity of brackish water yellow eels, Anguilla anguilla L. (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 17 (1986), S. 0 
    Details
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Female yellow eels, Anguilla anguilla L., were caught with fyke nets in the brackish water bight Hallangspollen, Norway during 1983 and 1984. Fishing was performed continuously for a variable number of days (defined as the fishing period), and the nets were monitored at uneven intervals during the fishing period. The eel activity, expressed as catch per unit effort (CPUE), was positively correlated (R2= 0·74; P 〈 0·001) with water temperature (defined as a regression of temperature variation during the fishing period). The multiple regression model of CPUE on water temperature was improved by including the number of fishing days in each fishing period in the regression model (R2= 0·91; P 〈 0·001). With high fishing efforts the predicted CPUE decreased below that which was predicted by the temperature model alone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2109.1986.tb00103.x
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  • 4
    Electronic Resource
    Electronic Resource
    Year class variation in fluctuating asymmetry in perch (Perca fluviatilis L.) from an acidic aluminium-rich lake (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Ecology of freshwater fish 4 (1995), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Fluctuating asymmetry is the random deviation from perfect bilateral symmetry owing to developmental perturbation, proposed as an indicator of sublethal environmental effects. This was measured in perch (Perca fluviatilis L.) from an acidic aluminium-rich lake. Eleven paired meristic and morphometric characters were scored for fluctuating asymmetry. Level of fluctuating asymmetry differed significantly between year classes for two of the meristic characters, lower extra gill rakers and upper extra gill rakers, and also for an index summarizing number of asymmetric meristic characters per individual. This year class variation in fluctuating asymmetry is probably due to large variation in water quality during early development of perch embryos in spring. For future work on fluctuating asymmetry on fish we recommend the use of as many year classes as possible in the analyses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0633.1995.tb00126.x
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  • 5
    Electronic Resource
    Electronic Resource
    Small-scale spatial variation in age and size at maturity of stream-dwelling brown trout, Salmo trutta (2005)
    Oxford, UK : Munksgaard International Publishers
    Ecology of freshwater fish 14 (2005), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract – This study documents substantial small-scale spatial variation in age and size at maturity of brown trout (Salmo trutta) found either in allopatry (above major waterfalls) or in sympatry (below waterfalls) with the Alpine bullhead (Cottus poecilopus) in forest streams in south-east Norway. Within two streams, female brown trout above waterfalls tended to delay the onset of sexual maturity, as compared with females from neighbouring sites below the waterfalls. Four additional streams were represented with either an allopatric or a sympatric site. There was considerable variation in age and size at maturity among these streams, but no consistent difference between allopatric and sympatric sites. It is suggested that the spatial variation in maturity responses is influenced by local opportunities for growth, and possibly also survival. Earlier studies in these streams have linked spatial variation in brown trout behaviour and demography to the presence or absence of the Alpine bullhead.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0633.2005.00094.x
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  • 6
    Electronic Resource
    Electronic Resource
    Individual variation in early life-history traits in brown trout (2000)
    Copenhagen : Munksgaard International Publishers
    Ecology of freshwater fish 9 (2000), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract – We studied the variability of early life history traits in individually raised progeny of brown trout Salmo trutta L. Eggs from two dams were each fertilized with sperm from 10 sires, producing 20 full-sib families. Each individual progeny was followed from fertilization until death without exogenous food. Egg size was positively correlated with a number of life-history traits, especially length and yolk sac volume at hatching and length at death, and these traits were strongly influenced by maternal effects. We found significant additive genetic variance for growth rate, length at death and life span without external food. Thus these early life-history traits may be modulated by natural selection. We found positive phenotypic and genetic correlations between most early life-history traits. However, life span without external food was negatively correlated with growth rate, indicating a genetic trade-off./〉
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0633.2000.eff090407.x
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  • 7
    Electronic Resource
    Electronic Resource
    Body depth variation in crucian carp Carassius carassius: an experimental individual-based study (2004)
    Oxford, UK : Munksgaard International Publishers
    Ecology of freshwater fish 13 (2004), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract –  Induced morphological defences, where individuals develop morphological structures as a response to signals from sympatric predators, are common among invertebrates. Such defences have also been reported in a freshwater fish, the crucian carp Carassius carassius. In crucian carp, the presence of piscivorous fish presumably induces the development of a deep body as a defence mechanism. We tested how the growth rate (in body depth, length and mass) of individually tagged crucian carp responds to pike Esox lucius odours and control water. In general, crucian carp exposed to pike odour grew better (both in length and mass) than control fish. The treatment crucian carp also developed deeper bodies than control crucian carp. Further, there was a strong positive relationship between individual growth rate and the rate of change in body depth and this relationship did not differ between control and treatment fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0633.2004.00048.x
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  • 8
    Electronic Resource
    Electronic Resource
    Life-history variation in perch (Perca fluviatilis L.) in five neighbouring Norwegian lakes (2002)
    Oxford, UK : Munksgaard International Publishers
    Ecology of freshwater fish 11 (2002), S. 0 
    Details
    ISSN: 1600-0633
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract – We have studied the population dynamics and reproductive biology of perch (Perca fluviatilis L.) from five neighbouring lakes in Norway. The lakes vary in water quality, varying from strongly acidified (pH≤5.0) to not acidified (pH≥6.0). Estimated annual survival rates did not differ among populations. There was no strong relationship between age at maturity in female perch and acidification. However, age at maturity was lower for female perch from the most acidic lake (c. 2 years) compared with perch in the four other lakes (2.5–3.5 years). There was no relationship between acidification level and size-adjusted egg size, fecundity or reproductive investment (Gonadosomatic index – GSI). Perch in the most acidified lake showed large variation in egg size, the lowest length-specific fecundity, the highest GSI, and the lowest age at maturity. Environmental stress, such as acidification, induces a number of changes to a lake community. It is therefore difficult to predict how acidification will influence the population dynamics and reproductive biology of a perch population.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1600-0633.2002.00023.x
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  • 9
    Electronic Resource
    Electronic Resource
    Geographic variation in life–history strategy of female roach, Rutilus rutilus (L.) (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 37 (1990), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Variation in growth rate, age at maturity, reproductive life span and reproductive investment was investigated in females only in seven populations of roach, Rutilus rutilus, in Norway. The growth rates of mature female roach were low, varying for most populations between 10 and 14 mm year.1 At the most northern locality the growth rate was only 5.6 mm year1. Individual fecundity and gonadosomatic index (GSI) varied unsystematically between populations, but it was evident that the population with the lowest growth rate also had the lowest individual fecundity and GSI. Egg weight also varied between populations, the most northern population had a medium egg weight, thus, in harsh climatic conditions egg number is sacrificed for a relatively high egg weight. We found no further evidence for a trade-off between egg number and egg size. Fecundity increased with length in all populations, whereas the variation in egg size and GSI for most populations did not covary with length or age. This fact, together with the high age at maturity in all populations and the long reproductive life spans supports the bet-hedging theory of life-history evolution. This is further supported by the fact that we did not find any correlation between the growth rates and the different descriptors of fitness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1990.tb03589.x
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  • 10
    Electronic Resource
    Electronic Resource
    Age determination and growth of yellow eels, Anguilla anguilla (L.), from a brackish water, Norway (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish biology 26 (1985), S. 0 
    Details
    ISSN: 1095-8649
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: This paper describes the age determination of European yellow eels from a brackish water area in south-east Norway. Two different methods were used; clearing in 96% ethanol or burning and cracking. When reading the otoliths twice using the same method, the same age was found in 40% of the readings, a discrepancy of 1 year was found in another 40% of the readings (both methods). Burning and cracking yielded age estimates which were on average 1.25 years higher than those obtained by clearing.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1095-8649.1985.tb04292.x
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