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UBC Theses and Dissertations

Some aspects of environmental variability in relation to stock recruitment systems Tautz, A. F.

Abstract

For a variety of stock-recruit systems in which environmental variability is simulated by random normal deviates used as multipliers or divisors Ricker (1958) and Larkin and Ricker (1964) demonstrated the benefits of complete stabilization of escapement as opposed to removal of a fixed proportion of the stock each year. Part I is primarily concerned with the response of these same systems to a pattern of stochastic modification which is more regular in form, a pattern such as might be imagined to result from long-term trends in environmental conditions. In addition, some mathematical properties of these systems are discussed. Part II considers the stock-recruit relationship from a more reductionist or mechanistic point of view. Evidence for differential utilization of spawning areas is presented and spawner distributions in three different environments are compared. These results are discussed in terms of their relevance to existing stock-recruit theory. Also, observations on egg retention and social facilitation are presented.

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