This thesis focuses on the implications of exploitation pattern (population selectivity) and population resilience for fisheries sustainability in the NE Atlantic. Novel metrics of exploitation pattern and resilience are introduced and the effects of juvenile protection and resilience erosion on stock size, structure and yields are investigated. Analysis of both empirical and simulated data suggested that high selection of juveniles negatively affects both stock size and yield. A meta-analysis of empirical data for 38 fish stocks showed that fishing mortality of juveniles exceeding half that of mature fish leads to overfishing. Simulation-based analysis illustrated that a mean age-at-capture more than two years higher than mean age-at-maturity secures high yields at low levels of stock depletion. The effects of exploitation pattern on stock status are weaker than those of exploitation rate when empirical data are considered, both at an individual-stock and a cross-stock scale. However, simulation-based analysis revealed that for higher levels of juvenile protection than the ones observed in most empirical stocks, exploitation pattern would be more influential than exploitation rate. These findings suggest that there is a high unfulfilled potential to promote sustainability by protecting juveniles. Besides exploitation pattern, population resilience is another factor whose role in fish population dynamics was examined here. A resilience assessment of Barents Sea cod was carried out using a novel integrated approach combining multivariate analysis and bifurcation theory. This way, the occurrence of a population state shift in 1981, associated with climatic and exploitation effects, was identified. The approach implemented in this resilience assessment is reproducible to any other data-rich population and can be also used at the community- and ecosystem-levels to explain and predict state shifts. As Europe is currently moving towards a more holistic approach in fisheries management through the reform of the Common Fisheries Policy, such quantification and investigation of stock/exploitation attributes beyond stock size and exploitation rate is of great importance.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:619166 |
| Date | January 2013 |
| Creators | Vasilakopoulos, Paraskevas |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=211300 |
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