More than 500,000 people tour the Carl Hayden Visitor Center at Glen Canyon Dam each year. The Bureau of Reclamation provides guided tours of the dam; stringent security measures have been in place since the September 11, 2001 terrorist attacks. The base of the dam can also be reached via boat from Lee's Ferry. Because of the cold, clear water released from Lake Powell, the stretch of the Colorado River between Glen Canyon Dam and Lee's Ferry has become an excellent rainbow trout fishery. Trout are not native to the Colorado River system; they were stocked in the river below Glen Canyon Dam after the dam was built. Other non-native fish such as smallmouth bass, striped bass, largemouth bass and black crappie were planted in Lake Powell to provide sport fishing opportunities.