Size selectivity of gill-nets and growth of roach

The analysis of catch selectivity of fishing equipment is a crucial step for the management of alien species in freshwater ecosystems. Roach Rutilus rutilus was introduced in many waterways in Italy often becoming the dominant species of the fish community and it is now considered potential pest. In Piediluco lake the species was first found in 2004 and its abundance has increased at a level that creates concern for the other fish species present in the lake. The growth of R. rutilus and the selectivity of gill-nets on its population were examined in Piediluco lake by analysing the selectivity of gill-nets of different mesh size. Sampling was conducted from January 2011 to October 2012 by means of gill-nets of different-sized mesh (8, 10, 12.5, 15.5, 19.5, 24, 28, 35, 45 and 55 mm). The results showed that R. rutilus in Piediluco lake had a growth faster and higher than in many other lake environments. The results of gill-nets selectivity gave important information to design a plan to control this species and confirmed that the use of suitable fishing techniques could be useful to manage the population of this alien species in Piediluco lake as well as in other similar environments.