Journal Article

Generalized compensation in stock-recruit functions: properties and implications for management

Elizabeth N. Brooks and Joseph E. Powers

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 64, issue 3, pages 413-424
Published in print April 2007 | ISSN: 1054-3139
Published online February 2007 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1093/icesjms/fsl046
Generalized compensation in stock-recruit functions: properties and implications for management

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Brooks, E. N., and Powers, J. E. 2007. Generalized compensation in stock-recruit functions: properties and implications for management. – ICES Journal of Marine Science, 64: 413–424.

A general stock-recruit function that explicitly defines density-dependent and -independent components of mortality over multiple stages is derived. By generalizing the stock-recruit function and the timing of density-dependent compensation, the impacts of different sources and magnitudes of mortality during the recruitment phase can be evaluated. Given reasonably comparable stage durations, compensation in early stages of a multistage process dominates density-independent effects; in later stages, density-dependent and -independent factors compete on a more even scale. Ratios of equilibrium statistics associated with the stock-recruit function under alternative compensation timing scenarios can be determined from the ratio of the compensation terms in the models when all scenarios assume the same type of stock-recruit function (Ricker or Beverton–Holt). This analytical result facilitates evaluation of proposed impacts or rehabilitation strategies without the need for a full stock assessment. Exogenous mortality has more impact on the maximum excess recruitment if that rate occurs later in the recruitment interval, especially if it takes place after compensation. Reparameterizing this generalized stock-recruit function in terms of steepness and virgin recruitment, we show that steepness is not influenced by the timing of compensation nor by the length of the recruitment interval; the level of virgin recruitment, however, is affected by both.

Keywords: bycatch fishing mortality; compensation; density-dependence; stock recruitment

Journal Article.  8501 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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