Abstract
In this thesis, I examine two important aspects surrounding salmonid reproductive
ecology, namely: (i) the problems with passing obstructions during
migratory spawning runs and (ii) how the early life stages in boreal
streams are influenced by increased levels of fine-grained particulate matter from drained
peatlands. These aspects are not only critical to salmonid reproductive success but have
grave implications regarding environmental quality and species conservation.
Spawning runs can be re-established by constructing fishways at obstructions
but the efficiency of fishways depends on several factors. The passage of multi-sea-winter
salmon was enhanced in the Isohaara fishway by increasing its water flow and by creating a
small waterfall at the entrance. The fishway, which consists of vertical slot and Denil
sections, proved to be unsuitable for most freshwater fish, whitefish and river lamprey,
whereas salmonids, once they had entered, successfully negotiated the fishway. In fishway
design, the migratory behaviour and the demands of the species of interest should be
considered. For salmonids, priority should be given to the attractiveness of the fish
entrance.
When there is a migration corridor, the availability and the quality of
spawning and rearing habitats has a major effect on the success of restoration projects. In
the humic rivers studied, the survival of incubated brown trout eggs was lower in riffles
susceptible to increased levels of fine-grained particulate matter from drained peatlands.
Additionally, an increase in the Fe content of high molecular weight dissolved organic
matter followed by its precipitation and sedimentation was proposed to be involved.
Correspondingly, the recapture rates of stocked yearling salmon were lower in the affected
riffles, individual salmon being smaller and thinner and having less food in their stomachs
than reference salmon. Based on these results, it seems probable that peatland drainage, by
influencing the incubation success of salmonid embryos and the foraging, growth and survival
of juveniles, eventually affects the number and quality of smolts produced. In future, such
water pollution control measures should be implemented that would enhance the success of
natural spawning and help ensure environmental quality.
| Identifer | oai:union.ndltd.org:oulo.fi/oai:oulu.fi:isbn951-42-5953-X |
| Date | 09 April 2001 |
| Creators | Laine, A. (Anne) |
| Publisher | University of Oulu |
| Source Sets | University of Oulu |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:eu-repo/semantics/publishedVersion |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess, © University of Oulu, 2001 |
| Relation | info:eu-repo/semantics/altIdentifier/pissn/0355-3191, info:eu-repo/semantics/altIdentifier/eissn/1796-220X |
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