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Title: Fish and their scales : on the power laws of aggregation, size distribution and trophic interaction
Author: Cobain, Matthew Robert David
ISNI:       0000 0004 7431 3229
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 2018
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Power law relationships are ubiquitous in ecology, and complex systems in general, and can be used as metrics to describe many aspects of ecosystem structure and function. While ecological interactions and processes predominantly occur at the individual level of biological organisation, currently, most ecological studies aim to estimate “typical” ecosystem behaviour over large spatial and temporal scales. This disconnect results in the under- appreciation of ecosystem dynamics that are potentially important for developing ecological theory and ecosystem modelling. The research presented herein aims to estimate within-ecosystem dynamics, as quantified by power law relationships, to test whether expected ecological dynamics can be captured effectively at smaller scales. I show that Taylor’s power law, a metric of aggregation, varies systematically, both spatially and temporally within the North Sea fish community, with the abiotic environment when populations were considered as cohorts of individual body sizes. By combining estimates of the power law distribution of body size in fish with stable isotopes that can be used to infer trophic interactions, I show that seasonal trends in fish movement patterns and the incorporation of pulsed phytoplankton production can be quantified in a highly dynamic estuarine environment. Estimates of the in situ community predator-prey mass ratio, which describes trophic behaviour, and the apparent trophic transfer efficiency are then derived and shown to exhibit strong seasonal variation, indicative of an estuarine food web that is temporally variable. Finally, I quantify the degree of individual specialisation, a mechanism by which intraspecific competition is modulated, in the diet of a commercially important but over-exploited fish species to inform conservation efforts. This work shows that ecological dynamics can be captured by a range of ecosystem metrics and that, therefore, small scale behaviours can be tested for empirically to direct ecosystem models and theory.
Supervisor: Trueman, Clive Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available