public hunting areas. Water management The wetland managers for both the private hunting clubs and the state's public land take water from major and minor sloughs throughout the marsh. Montezuma Slough, one of the largest, is open at both ends, and its flood tide current is longer and stronger than its ebb tide current, causing a net west-to-east flow which draws higher saline water eastward from Grizzly Bay. The flood tide pushing through the slough takes half an hour longer to traverse the marsh than does the matching flood tide following the more direct route in the main Suisin Bay channel. Thus, high tide at the east end of the slough arrives out of phase with high tide in the main channel, and rather than being pushed back, as it would be in the main channel or in a dead-end slough, the slough water keeps flowing eastward, drawing more saline water with it. To meet the salinity requirements stipulated by the California Water Resources Control Board to support "beneficial uses" in Decision-1485, the California State Water Project and the federal Central Valley Project built the Montezuma Slough Salinity Control Gates. They began operation in 1989. The gates span Montezuma Slough near the Roaring River intake and are periodically operated from October to May to meet the more recently established salinity standards set by Decision-1641, to block the salty flood tide from Grizzly Bay but allow passage of the freshwater ebb tide from the mouth of the Sacramento-San Joaquin Delta. Because the Salinity Control Gates are more effective than anticipated other proposed salinity control measures were abandoned. The gates operate as needed from October through May. Fish Although the Suisun Marsh is managed for waterfowl, it is also an important fish habitat, especially for wild salmon. Monitoring stations throughout the marsh measure the impact of water management activities on fish populations, and fish screens prevent the diversion and entrapment of fish in the waterfowl ponds. The Marsh supports 80% of the state's commercial salmon fishery by providing important tidal rearing areas for juvenile fish allowing them to grow twice as fast as those reared in the upper watershed, thus, greatly enhancing their survival. And is an important area for native fishes including the delta smelt which is protected by the federal Endangered Species Act. Flora Suisun Marsh is home to the only two known occurrences of the Suisun thistle, Cirsium hydrophilum