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Genetic and Ecological Consequences of Fish Releases: With Focus on Supportive Breeding of Brown Trout Salmo trutta and Translocation of European Eel Anguilla anguilla
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Evolutionary Biology, Population Biology.
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Although the practice of releasing fish into the wild is common in the management and conservation of fish populations, the success of release programmes and the potential harmful genetic and ecological effects that may follow are rarely considered. This thesis focuses on genetic and ecological consequences of fish releases, exemplified by supportive breeding of brown trout (Salmo trutta) and translocation of European eel (Anguilla anguilla). Specific questions addressed include: What is the relative performance of hatchery produced fish released to support wild populations, and do released hatchery fish contribute to the natural productivity? What is the variation in reproductive success in the wild, and how does it affect the genetic consequences of a supportive breeding programme? Is there a spatial genetic structure in the European eel that must be considered in the management of this rapidly declining species?

Experiments conducted under natural and near-natural conditions in the River Dalälven, Sweden, suggest that hatchery produced trout can reproduce in the wild. In fact, when the pronounced variation between individual breeders was accounted for, there were no detectable differences between hatchery produced and wild born trout in reproductive success or offspring survival. These results were supported by molecular genetic data suggesting a pronounced gene flow from hatchery to wild trout in the river. Hatchery reared trout were, however, found to exhibit reduced survival rates immediately following release into the wild, an effect that was most likely due to phenotypic responses to the hatchery environment during ontogeny and a lack of experience of the wild.

In sharp contrast to recently published studies, the present genetic analyses of European eels sampled across the whole distribution range suggest no spatial genetic structure but a subtle temporal genetic heterogeneity within sampled locations. These results emphasise the need to consider temporal replication when assessing population structure of marine species.

The results obtained have general implications for the management and conservation of fish populations. First, supportive breeding of threatened salmonid populations might be successful, not only for boosting the census size and thereby reducing the short-term probability of extinction, but also for reducing the risks of inbreeding depression and loss of adaptive potential in future generations. However, the results also highlight the need to restore the natural productivity of a population under supportive breeding to avoid a potential reduction in fitness due to hatchery selection. Further, the lack of a detectable spatial genetic structure in the European eel suggests that the management strategy of translocating juvenile eels from locations were they are overabundant to other suitable freshwater habitats does not necessarily have to include genetic considerations with respect to the geographical origin of the translocated eels.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2003. , p. 36
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 906
Keyword [en]
Biology, conservation, fishery management, panmixia, genetic variation, effective population size, hatchery selection
Keyword [sv]
Biologi
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-3764ISBN: 91-554-5796-7 (print)OAI: oai:DiVA.org:uu-3764DiVA, id: diva2:163619
Public defence
2003-12-05, Ekman salen, Uppsala, 14:00
Opponent
Supervisors
Available from: 2003-11-13 Created: 2003-11-13Bibliographically approved
List of papers
1. Effects of sea-ranching and family background on fitness traits in brown trout Salmo trutta reared under near-natural conditions
Open this publication in new window or tab >>Effects of sea-ranching and family background on fitness traits in brown trout Salmo trutta reared under near-natural conditions
2003 In: Journal of Applied Ecology, ISSN 0021-8901, Vol. 40, no 2, p. 241-250Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-91038 (URN)
Available from: 2003-11-13 Created: 2003-11-13Bibliographically approved
2. Lack of molecular genetic divergence between sea-ranched and wild sea trout (Salmo trutta)
Open this publication in new window or tab >>Lack of molecular genetic divergence between sea-ranched and wild sea trout (Salmo trutta)
Show others...
2003 In: Molecular Ecology, ISSN 0962-1083, Vol. 12, no 8, p. 2057-2071Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-91039 (URN)
Available from: 2003-11-13 Created: 2003-11-13Bibliographically approved
3. Reproductive success of hatchery produced and wild born brown trout Salmo trutta in an experimental stream
Open this publication in new window or tab >>Reproductive success of hatchery produced and wild born brown trout Salmo trutta in an experimental stream
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2004 (English)In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 41, no 2, p. 355-364Article in journal (Refereed) Published
Abstract [en]

1.Although releases of hatchery-produced salmonids to support conspecific wildpopulations have increased dramatically during recent decades, little information isavailable about the performance in the wild of hatchery fish and their offspring.Important factors determining the success and genetic outcomes of supportive breedingprogrammes include (i) the relative reproductive success of released hatchery fish in thewild, and (ii) the extent to which the propagation affects the variance in reproductivesuccess in the population as a whole.2.We performed two field experiments on brown troutSalmo truttafrom the RiverDalälven in Sweden, where we examined reproductive success in an experimental stream.In experiment 1 we compared reproductive success between trout from a seventhgenerationhatchery stock of native origin and wild-born trout from the river. In experiment2, we compared reproductive success between seventh-generation hatchery troutand hatchery-reared trout derived from wild-born parents. Individual reproductivesuccess, based on the number of offspring assigned using microsatellite markers, wasassessed on three occasions after reproduction: immediately after hatching and after thefirst and second growth seasons.3.In experiment 1 there were no significant differences in reproductive success betweenseventh-generation hatchery trout and wild-born trout. In experiment 2, males from wildbornparents were more successful than males from the seventh-generation hatcherystock, but this difference was not observed among females.4.There was some evidence for a positive association between body size and reproductivesuccess among females but not males. For males, the number of mates was significantlyassociated with reproductive success, but this relationship was not evident among females.5.The variance in reproductive success was pronounced in both experiments, yieldingestimates of the ratio between the genetically effective size and the census size of ourexperimental populations ranging from 0·12 to 0·59.6.Synthesis and applications. Our results suggest that the reproductive success in thewild of hatchery-produced and wild-born trout with a common genetic backgroundmay be rather similar. These findings, in combination with the pronounced variancein reproductive success observed among breeders, indicate that supportive breedingcan be managed to increase not only the census but also the genetically effective sizeof small, endangered salmonid populations. However, to minimize negative effects ofhatchery selection, it is important to give priority to the restoration of natural habitatsand thereby increase the reproductive output from individuals in the wild.

Keyword
conservation, domestication, effective population size, microsatellite DNA, supportive breeding
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-91040 (URN)10.1111/j.0021-8901.2004.00895.x (DOI)
Available from: 2003-11-13 Created: 2003-11-13 Last updated: 2017-12-14Bibliographically approved
4. Survival, morphology and phenotypic plasticity of wild and sea-ranched brown trout stocked as eyed eggs or as 0+ parr
Open this publication in new window or tab >>Survival, morphology and phenotypic plasticity of wild and sea-ranched brown trout stocked as eyed eggs or as 0+ parr
Manuscript (Other academic)
Identifiers
urn:nbn:se:uu:diva-91041 (URN)
Available from: 2003-11-13 Created: 2003-11-13 Last updated: 2010-01-13Bibliographically approved
5. Lack of a temporally stable genetic structure in the European eel: the panmixia hypothesis revisited
Open this publication in new window or tab >>Lack of a temporally stable genetic structure in the European eel: the panmixia hypothesis revisited
Show others...
Manuscript (Other academic)
Identifiers
urn:nbn:se:uu:diva-91042 (URN)
Available from: 2003-11-13 Created: 2003-11-13 Last updated: 2010-01-13Bibliographically approved

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