Proposed standard weight (Ws) equations for Telestes muticellus (Bonaparte, 1837) in the River Tiber basin

Relative weight (Wr) is a body condition index that enables the evaluation of the wellbeing of fish by comparing the actual weight of a specimen with the ideal weight of a specimen of the same species and same length, in good physiological condition, i.e., standard weight (Ws). Two methods of calculating standard weight are proposed in the literature: the RLP and the EmP method. The main aim of this study was to work out standard weight equations for Italian riffle dace, Telestes muticellus, in the Tiber River basin. To this end, length and weight measurements of 9,186 specimens from 57 watercourses in the Tiber River basin were analysed. The resulting standard weight equations were: log10 (Ws) = -5.085 + 3.081 log10 (TL) for RLP method and log10 (Ws) = -3.706 + 1.685 log10 (TL) + 0.349 [log10 (TL)]2 for EmP method. A further aim of this research was to compare the performance of the two proposed methods (RL P and EmP). The use of the EmP Ws equation to compute Wr of Italian riffle dace in the Tiber River basin is suggested, as it proved not to be influenced by length-related bias.