A continuous diphasic model for prediction of survival of cultivated populations when affected by disease: the case of shrimp and white spot disease

Abstract

High mortalities following disease outbreaks can importantly reduce cultivated populations and result in economic losses. In this study, we present a continuous diphasic model (CDM) for dynamic prediction of survival of shrimp population, when affected by white spot disease (WSD). The model allows describing a smooth transition between two phases that correspond to survival before and after die-offs caused by the disease. The CDM is statistically compared with a discontinuous diphasic model (DDM) reported by us in a previous investigation. Data from intensive commercial ponds were used for model comparison. Residual sum of squares ranged from 3.1 to 105.7 (CDM) and from 3.9 to 270.1 (DDM), indicating better fitting and higher flexibility of the CDM in all the cases analysed. The CDM was more adequate for describing the transition between phases, regardless of either the time when the transition occurred, the speed of the transition and the total mortality occurring during the transition. We provide scripts in MATLAB code of the procedure to fit the CDM. We conclude that the CDM is adequate to dynamically modelling survival of cultivated shrimp populations when affected by WSD. The model could be tested for other cultivated populations when affected by disease.