Stress test of a biological early warning system with zebrafish (Danio rerio)

João Amorim, Miguel Fernandes, Vitor Vasconcelos, Luis Oliva Teles

The aim of this work was to develop a novel methodology to stress test the diagnostic capability of a video tracking system with zebrafish (Danio rerio), against two pre-established disturbances. Eight different treatments were tested varying the presence or absence of a toxicant (NaOCl) and two disturbances: the passing of a shadow (mimicking a predator) and entrapment of the fish. The concentration tested corresponded to a sublethal (1 % 24 h-LC50) and short term exposure (2 h). A total of 56 organisms were tested resulting in 112 diagnoses (before and after the contamination). A statistical model of diagnosis was developed using Self-organizing Map (SOM) and Correspondence Analysis (CA). Sensitivity, specificity, accuracy, false positive and false negative values were calculated to evaluate the diagnostic performance. The disturbances did not negatively affect the capability of the model. In the presence of at least one of these variables, the diagnostic performance was similar or even superior to the baseline results without disturbances. Furthermore, the system produced a large number of correct diagnoses, at an ecologically relevant concentration of exposure, in a non-invasive way.