Guy W. Fleischer
James R. Bence
Emily B. Szalai
2003
A concurrent increase in lakewide abundance and decrease in size-at-age of bloater (<i>Coregonus hoyi</i>) in Lake Michigan have suggested density-dependent growth regulation. We investigated these temporal patterns by fitting a dynamic von Bertalanffy model and lengthweight relationship with time-varying parameters to mean length- and weight-at-ages (ages 17) from annual surveys (1965-1999). We modeled yearling length, asymptotic size (<i>L</i>‰), and the parameters of a power relationship between mean weight and mean length (α and β) as changing slowly over time using a random walk model. The Brody growth coefficient (<i>k</i>) was modeled as a linear function of <i>L</i>‰ with year-specific random deviations. Our results support a positive relationship between <i>L</i>‰ and <i>k</i>, indicating that under conditions supporting larger asymptotic lengths, individuals approach the asymptote more rapidly. We explored the relationship between year-specific growth parameters and indices of lakewide bloater abundance and found evidence of density-dependent growth. However, in the most recent years, <i>L</i>‰ and yearling length have remained low in Lake Michigan despite low bloater abundances, suggesting the occurrence of a fundamental shift in the food web.
application/pdf
10.1139/f03-003
en
NRC Research Press
Modeling time-varying growth using a generalized von Bertalanffy model with application to bloater (Coregonus hoyi) growth dynamics in Lake Michigan
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