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Schaarschmidt, U.

Publications and source records attributed to Schaarschmidt, U..

2 recordsLinked to original sources

Discrete Time Modeling of Stock-Recruit Relationships with Life-History Stanzas

The stock-recruit relationship is a foundational concept in fisheries science, bridging the connection between parental populations (stock) and progeny (recruits). Traditional approaches describe this relationship using closedform analytical functions, which represent only a restricted subset of the broader class of possibilities. This paper advocates for a novel approach that integrates discrete time modeling with a life-history cycle framework, incorporating distinct stanzas and developmental processes. By breaking down the life cycle into identifiable stages, we capture the step-wise progression of life history traits and the factors influencing recruitment outcomes. Through numerical simulations, we explore the advantages of this approach, including complexity handling, dynamic behavior modeling, and scenario exploration. Our simulation results show that we are able to generate a broad spectrum of stock-recruit relationships (including the traditional ones), which best reflect variability observed in nature. We demonstrate how this framework allows for the identification of critical stages, and integration of various factors that influence recruitment. This holistic approach enhances our comprehension of the intricate interactions shaping stock-recruit relationships and advances our understanding of sustainable population dynamics. HighlightsO_LIA novel multi-stage life-cycle model is presented. C_LIO_LIModel simulations reveal three different Stock-Recruitment (SR) patterns. C_LIO_LIOur approach contributes to enhanced understanding of SR relationships. C_LI

ecology↗

Mathematical Preconditions for Existence of the Stock-Recruitment Function

For marine species, several life stages link parents to their progeny (recruits), through a process referred to as recruitment. Current stock recruitment (SR) functions encapsulate this multi-stage relationship in a closed-form mathematical expression, which explicitly relates the biomass of parents, to the number of recruits. This functional relationship (between parents and recruits) is required for management purposes. No study, however, has investigated the conditions that validate the existence of the SR functions when all life history stages are incorporated into a model. In this study, we represent the processes leading to recruitment by a stage-and age-structured discrete-time population dynamic model. We show that in general, a SR function does not correctly represent the parent-progeny relationship. A valid relationship must incorporate information across the complete life cycle over several time periods. For populations with simple life cycle history, a functional relationship may result, which is not necessarily consistent with current SR functions. We present a brief discussion of the relevance of our results to effective management of fisheries.

ecology↗