Temporal variations in Lago Maggiore and its fish assemblage: the role of trophic status, climate and fishery with emphasys on the slow growing coregonid C. macrophthalmus (Nusslin, 1882)

Lake Maggiore is the second largest and deepest lake in Italy and one of the largest lake in the Mediterranean Ecoregion. A long series of limnological, biological and fishery informations, garhered by the International Commission for the Protection of ItalinSwiss waters and the Italian Swiss Fishery Commission, exists. These data altoghther represents a good opportunity to investigate the links between environmental and anthropogenic stressors on its biotic community, including fish. Altrhough studies have been already carried on the long term changes of lower components of the food webs, fishes have been excluded until now. In this study we review historical published and unpublished informations in combination with most recent data from fishery and gillnet survey in order to describe long term changes in the fish community of Lake Maggiore. As a specific case study we focuse on the coregonid C. macropthalmus (Nusslin, 1882) the most abundant fish species in the commercial cathches. We analyze a body growth data series of 30 years collected by CNR Institute of Ecosystem Study from 1960 to 2010 which covers the period of eutrophication (ca 1960-1975), re-oligotrophication (1980-1995), warming (1995-2010) including the period of a fishing ban (1996-2003). The observed changes are then interpreted in the light of the environmental and authropogenic pressures