Abstract

Demographic responses of a commensal annelid of freshwater crayfish, Stratiodrilus aeglaphilus, to a sublethal organic enrichment were tested. Censuses of the S. aeglaphilus population were performed every 3 days during a 27 days period. The demographic variables were estimated using a quadratic programming method. Population growth rate (λ) was 1.0230 in the control, and 0.9145 in the organic enrichment treatment, it was indicating positive growing and decrease, respectively. Decomposition analysis showed an antagonistic response of the demographic parameters to organic enrichment, with negative contributions from eggs and juveniles stasis and growing probabilities, and positive contributions from adults survival and fecundity. After the organic enrichment, the positive effect on adults could not compensate the adverse effect on the early stages, thus causing a reduction of the population density of S. aeglaphilus. © 2007 Springer Science+Business Media B.V.