The consequences of individual variability in moulting probability and the aggregation of stages for modelling copepod population dynamics
Souissi, S.; Ban, S. (2001). The consequences of individual variability in moulting probability and the aggregation of stages for modelling copepod population dynamics. J. Plankton Res. 23(11): 1279-1296
In: Journal of Plankton Research. Oxford University Press: New York,. ISSN 0142-7873; e-ISSN 1464-3774, more
Individual variability in development rates of the calanoid copepod Eurytemora affinis was studied using previously published data that are here normalised for the effects of food and temperature. The late-developing individuals died before reaching the adult stage. The development of individuals was studied using two different stage aggregations. In the one case, the stages were aggregated into four groups: early nauplii (N1-N3), later nauplii (N4-N6), early copepodites (C1-C3) and later copepodites (C4-C5). In another case, only total nauplii (N1-N6) and total copepodites (C1-C5) were used. The distributions of development time in the first groups obtained from the normalised data show distinct asymmetry. The gamma density function is asymmetrical to fit the distributions of development in the different groups under different experimental conditions. For one experimental condition (103 cells ml-1, 15°C) the development of E. affinis was simulated using an age-within-stage model together with the fitted distributions of moulting probabilities. We showed that the asymmetrical gamma distribution was an adequate parameterization of the transfer process. It was also useful to simplify the life cycle representation by lumping developmental stages. However, the comparison of the simulated abundance with two life cycle representations showed another source of error due to the heterogeneity of stage-specific mortality rates. The error of the estimation increases in proportion to the difference of mortality rates between two successive stages.
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