  The growth of Aeromonas hydrophila and aerobic natural flora (APC) on
gilthead seabream surfaces was evaluated during the refrigerated storage (21
days). The related growth curves were compared with those obtained by a
conventional third order predictive model obtaining a low agreement between
observed and predicted data (Root Mean Squared Error = 1.77 for Aeromonas
hydrophila and 0.64 for APC). The Lotka-Volterra interspecific competition
model was used in order to calculate the degree of interaction between the two
bacterial populations (\beta_{Ah/APC} and \beta{APC/Ah}, respectively, the
interspecific competition coefficients of APC on Aeromonas hydrophila and
vice-versa). Afterwards, the Lotka-Volterra equations were applied as tertiary
predictive model, taking into account, simultaneously, the environmental
fluctuations and the bacterial interspecific competition. This approach allowed
to obtain a best fitting to the observed mean growth curves with a Root Mean
Squared Error of 0.09 for Aeromonas hydrophila and 0.28 for APC. Finally,
authors carry out some considerations about the necessary use of competitive
models in the context of the new trends in predictive microbiology.
