We took advantage of an opportunity to sample populations of non-native predatory fish in one of the marshes created and managed by the Natomas Basin Conservancy when the marsh was drained for routine maintenance purposes. Both largemouth bass and green sunfish were present in the marsh. Green sunfish appear to be too small to pose a significant risk of predation to giant garter snakes, although they may compete with giant garter snakes for prey. Largemouth bass pose a greater risk to giant garter snakes and management actions to control their populations may become necessary in the future.