Fish survey in Angitola lake: in field non-invasive evaluation of weight

The Angitola FISH2O project, granted by Calabria FEP 2007-13 (Code 02/BA/12), aim to survey biodiversity in aquatic ecosystems, in which fishes should represent the main trophic resource within the various food chains relative to the Angitola lake. The final objective is to obtain a monitoring of various species by means of non-invasive techniques. According to Water Framework Directive (2000/60/EC), capturing and manipulations of animals were minimized, and the subjects captured were promptly released. Two areas, unequivocally identified by GPS coordinate, were selected at 4 and 10 meters of depths, in which fishing nets1 were positioned. Captured fishes were all manipulated as follows: 1) removed by nets by cutting wires and minimizing stress; 2) placed in basins filled with water; 3) weighted, with an electronic scale, and measured; 4) photographed; 5) clinically evaluated; 6) released as soon as possible. The dead subjects (n=28) were preserved in a portable fridge; they belonged to the following species: Carassius carassius (n=10), Perca fluviatilis (n=8), and Squalius cephalus (n=10). Data collected allowed developing a linear relation between length and weight. The resulting prediction equations and the correlation coefficients (r2) are summarized in table 1. Such equations are intended to have the precision reported only in the species and the sizes described. Even if a more accurate method, which might include all three dimensions of fishes, should be analyzed, accuracy of this method, proved by the high values of r2 is fully acceptable not only in common species but even more in vulnerable and endangered species.