Population ecology of landlocked Arctic charr, Salvelinus alpinus L ., in the Canadian High Arctic
The thesis describes fieldwork conducted during the Joint Services Expeditions to Ellesmere Island 1988, 1991 and subsequent modelling activities. Four landlocked populations of Arctic charr, Salvelinus alpinus L., were surveyed at 81 oN, close to the northerly extreme of the species range. They wer...
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| Format: | Thesis |
| Language: | unknown |
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The Open University
1996
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| Online Access: | https://dx.doi.org/10.21954/ou.ro.0000e0d8 http://oro.open.ac.uk/id/eprint/57560 |
| Summary: | The thesis describes fieldwork conducted during the Joint Services Expeditions to Ellesmere Island 1988, 1991 and subsequent modelling activities. Four landlocked populations of Arctic charr, Salvelinus alpinus L., were surveyed at 81 oN, close to the northerly extreme of the species range. They were single-species populations consisting of two distinct size modes, "Dwarf" and "Normal" charr, but with major differences both in size and relative numbers between the lakes. Tentative correlations between population structure, growth rate variation and possible genetic divergence are suggested by this fieldwork and the models examine their credibility. The key hypothesis is that the alternative life history strategies represented by Dwarf and Normal charr represent different solutions to the problem of energy limitation within a size-structured population. Major findings of the models are that alternative life history strategies should be expected to be optimised at different growth rates; density dependence implies that Dwarfs and Normals have equal fitness; a high average juvenile growth rate is likely to lead to a large number of Normals relative to Dwarfs; and that maximum individual fitness is probably achieved in bimodal populations within a "semi-speciated" condition. A combination of evidence further suggests that cannibalism is a likely mechanism for maintenance of the bimodal population structures; and the form of a reaction norm for choice of life history strategy is predicted and found to be similar to one experimentally determined for smolting in Atlantic salmon, Salmo salar L .. |
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