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A unified treatment of top-down and bottom-up control of reproduction in populations

Authors

  • Stephan B. Munch,

    1. Center for Stock Assessment Research, Department of Applied Mathematics and Statistics, University of California Santa Cruz, CA 95064, USA
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  • Melissa L. Snover,

    1. Pacific Fisheries Environmental Laboratory, NOAA Fisheries, 1352 Lighthouse Avenue, Pacific Grove, CA 93950, USA
    2. Joint Institute for Marine and Atmospheric Research, University of Hawaii, 1000 Pope Road, Honolulu, HI 96882, USA
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  • George M. Watters,

    1. Pacific Fisheries Environmental Laboratory, NOAA Fisheries, 1352 Lighthouse Avenue, Pacific Grove, CA 93950, USA
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  • Marc Mangel

    Corresponding author
    1. Center for Stock Assessment Research, Department of Applied Mathematics and Statistics, University of California Santa Cruz, CA 95064, USA
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E-mail: msmangel@ucsc.edu

Abstract

Generalizations describing how top-down and bottom-up processes jointly influence the production of offspring (recruitment) and the number of reproducing adults are lacking. This is a deficiency because (1) it is widely recognized that both top-down and bottom-up processes are common in ecosystems; and (2) the relationship between the number of individuals recruiting and number of reproductively active individuals present in that population is of fundamental importance in all branches of ecology. Here we derive a model to consider the joint effects of top-down and bottom-up forcing in any ecosystem. In general, during the lifetime of a cohort, bottom-up effects are likely to limit recruitment over longer periods of time than top-down effects. Top-down effects are likely to be most important early in the life history when potential recruits are small in size, and such effects will be more recognizable in small cohorts comprised of slowly growing individuals.

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