Invasive species plaque Venice Lagoon

It was interesting to hear Professor Pastres of the University of Venice talk about invasive species in the Venice Lagoon and their effect on the fisheries.  He talked about the introduction of Manila clams in aquaculture, there rapid rise in population and the resulting collapse from over harvest.  He also hinted at an invasive species which preys on the native fish population and is decimating the local fishery.  he was not able to provide any economic data on the effects of invasive species on the local economy.