Technical contribution Length–weight and length–length relationships for cavedano chub Squalius squalus (Bonaparte, 1837) in Italy By D. Giannetto 1 , A. Carosi 1 , L. Ghetti 2 , G. Maio 3 , E. Pizzul 4 , L. Pompei 1 , P. Turin 5 and M. Lorenzoni 1 1 Dipartimento di Biologia Cellulare e Ambientale, Universit  a di Perugia, Perugia, Italy; 2 Regione dell’Umbria, Servizio Programmazione Forestale, Perugia, Italy; 3 Aquaprogram s.r.l., Vicenza, Italy; 4 Dipartimento di Scienze della Vita, Universit  a di Trieste, Trieste, Italy; 5 Bioprogramm s.c., Padova, Italy Summary Data of 31496 specimens of cavedano chub Squalius squalus were collected in 89 different waterbodies distributed geo- graphically throughout Italy and used to provide length– weight and length–length relationship for this species. The linear relationship between total length (TL) and standard length (SL) was described by the equation TL (cm) = 4.007 + 0.874 SL (cm). The resulting total length– weight equation for cavedano chub in Italy was: log 10 W = À2.121 + 3.083 log 10 TL (cm). Introduction Analyses of length–weight relationships can provide impor- tant insight into the ecology of a species and the assess- ment of its populations (Froese, 2006). For example, it allows between-region comparisons of life histories of a certain species (Moutopoulos and Stergiou, 2002), or the evaluation of biomass through length (Tsoumani et al., 2006). Cavedano chub Squalius squalus (Bonaparte, 1837) is a cyprinid endemic in the Italian peninsula and the Balkans (Skadar and Ohrid basins) (Kottelat and Freyhof, 2007), inhabiting the intermediary stretches of the watercourses (Lorenzoni et al., 2006). Although it is one of the most widespread freshwater fishes in Italy (Pompei et al., 2011), information on this species in Italian waterbodies is limited (Lorenzoni et al., 2011) also because it was assimilated with the congeneric European chub S. cephalus (Linnaeus, 1758) (Giannetto et al., 2012). It is only recently that studies based on mor- phological and molecular analysis confirmed the separation of cavedano chub and European chub into two different species (Kottelat and Freyhof, 2007; Gigliarelli et al., 2012), and no estimates on length–weight relationships for this species are available in FishBase (Froese and Pauly, 2012). The main aim of this study was to provide length–weight and length–length relationship for cavedano chub S. squalus in Italy. Materials and methods Length and weight data on cavedano chub were collected by electrofishing in different waterbodies throughout Italy. For all fish caught in the field, total length (TL in cm) was mea- sured to the nearest millimeter and weight (W in g) was determined with a digital balance to an accuracy of 0.1 g. After measurement, all fish were released at the site of capture. Conversion of lengths measured in terms of standard length (SL) to total length (TL) was done using the linear regression model, developed by using all fish in the dataset for which SL and TL measurements were recorded: TL ðcmÞ¼ 4:007 þ 0:874SLðcmÞ ðR 2 ¼ 0:998; P < 0:001; n ¼ 1087Þ: Weights and lengths were log transformed and the LWR for the total sample was determined by the equation log 10 W = log 10 a + b log 10 TL (cm), where a is the intercept on the Y-axis of the regression curve and b is the regression coefficient. The difference between the value of b of the LWR and the value of isometric growth (b = 3) were then compared by t-test. Finally, a LWR was determined for each population separately and a linear plot between the slopes (b) against all intercepts (a) of all populations was calcu- lated. Results and discussion During the research 31496 specimens were analyzed from 89 waterbodies throughout Italy. Captured fish ranged in size from 2 to 49.4 cm (mean Æ SE = 147.973 cm Æ 80.042) and in weight from 0.1 to 1855 g (mean Æ SE = 66.9 g Æ 118.005). The LWR based on the total dataset was: log 10 W ¼À2:121 þ 3:083 log 10 TLðcmÞ ðR 2 ¼ 0:986; P < 0:001; TL range 2–49:4 cm; n ¼ 31496Þ: The value of b of the LWR (3.083) was higher than 3, indicating an isometric growth. This emphasized a positive J. Appl. Ichthyol. (2013), 1–2 © 2013 Blackwell Verlag GmbH ISSN 0175–8659 Received: April 17, 2013 Accepted: October 10, 2013 doi: 10.1111/jai.12384 Applied Ichthyology Journal of