Ecology and management of range edge populations: the case of toothfish species at the South Sandwich Islands
Current theory suggests that the life history of a species will vary in a predictable way from the range centre where habitat is likely to be optimal, to range peripheries where it is not. Moving towards cold water, high-latitude range edges, life history theory contends that individuals should exhi...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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Division of Ecology and Evolution, Imperial College London
2012
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| Online Access: | http://hdl.handle.net/10044/1/9969 https://doi.org/10.25560/9969 |
| Summary: | Current theory suggests that the life history of a species will vary in a predictable way from the range centre where habitat is likely to be optimal, to range peripheries where it is not. Moving towards cold water, high-latitude range edges, life history theory contends that individuals should exhibit reduced growth rates to an increased average maximum length, with delayed maturation and reduced somatic condition. In addition, increased recruitment variability should be observed towards range edges. Toothfish species Dissostichus eleginoides and D. mawsoni are large deep-water finfish predators of the Southern Ocean region. Both are found at the South Sandwich Islands in the South Atlantic Ocean, where they are situated on the edge of their distributional range. In this study, data collected on board commercial fishing vessels were used to describe the ecology, life history and dispersal patterns of range-edge toothfish populations, compared with those of range centre populations (South Georgia D. eleginoides and Ross Sea D. mawsoni). Two main research questions were addressed: 1. What limits the distribution of toothfish species populations at the South Sandwich Islands and how do range edge life history and population dynamics differ from those of range centre populations? 2. How can we use this information to more effectively manage the toothfish fishery at the South Sandwich Islands and other fisheries on range edge populations? A bioregional analysis made use of commercial longline data to resolve the position of the ecotone between the Antarctic and Subantarctic bioregions at the South Sandwich Islands. An abrupt transition was observed between the two bioregions around Saunders Island and this was spatially coincident for finfish and invertebrate communities, indicating a dramatic change in habitat type at this location. A correlative modelling analysis suggested that the formation of toothfish species range edges is influenced by the extent of sea ice cover and winter seawater temperature near the ... |
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