Alosa to detect ultrasound (at frequencies above 20 kHz, which is the limit of human hearing). This was first discovered by fisheries biologists studying a type of shad known as blueback herring, and was later verified in laboratory studies of hearing in American shad. This ability is thought to help them avoid dolphins that find prey using echolocation. "Alosa" species are generally pelagic. They are mostly anadromous or semianadromous with the exception of strictly freshwater landlocked species. "Alosa" species are generally migratory and schooling fish. Males usually mature about a year before females; they spawn in the late spring to summer.
Malden River They can be caught from the Malden River with simple food baits—such as corn or bread—on the bottom of the river. Another fish is the alewife and its cousin, the blueback herring, collectively known as river herring or simply herring. Both migrate from the ocean into the fresh water of the Malden River every spring to spawn. Striped bass, a prized saltwater fish, also come in from the ocean to spawn and prey on the herring. Other fish, like bluegill, largemouth bass, and catfish, are less common. The Native Americans and settlers used the Malden River for recreation and commercial