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.
American herring gull American herring gull The American herring gull or Smithsonian gull ("Larus smithsonianus" or "Larus argentatus smithsonianus") is a large gull that breeds in North America, where it is treated by the American Ornithologists' Union as a subspecies of herring gull ("L. argentatus"). Adults are white with gray back and wings, black wingtips with white spots, and pink legs. Immature birds are gray-brown and are darker and more uniform than European herring gulls, with a darker tail. It occurs in a variety of habitats including coasts, lakes, rivers and garbage dumps. Its broad diet includes invertebrates, fish, and many other items.