The Seine used to be heavily polluted, with many factories dumping their waste directly into the river. By the 1950s there were only four or five species of fish left. Strict environmental regulations and water treatment technology have cleaned up the river, and today there are over three dozen species of fish (mostly silver carp, catfish, pike perch, eels, rainbow trout and perch) and an abundance of aquatic birds and plants. The Seine is still used by commercial shipping barges, although most of the boats passing under the scenic bridges of Paris are pleasure craft – such as sightseeing or dinner cruises.