Factors affecting migration patterns of juvenile river herring in a coastal Massachusetts stream

摘要: Juvenile anadromous river herring (alewives, Alosa pseudoharengus, and blueback herring, aestivalis) spend 3–7 months in freshwater before migrating to the ocean, often exhibiting waves of early late migrations. Migratory patterns associated abiotic biotic factors were examined for both species 2003 from Herring River Bourne Massachusetts. Migrating grouped into two temporal periods separated by species. Relationships between (water temperature, lunar phase, precipitation) (size, age, growth rate, hatch date) timing out-migration (transition seawater) examined. Blueback migration coincided with a sharp decrease temperature consistent time year. Peaks alewive may reflect adaptive traits maximizing likelihood survival through seasonal marginal stream habitats also avoiding lethal water temperatures winter. bluebacks exhibited single migratory period (late September–October) which occurred pulses alewives. These represent distinct strategies alewives herring. Early be mechanism such as competition low food availability are mitigated. In contrast, environmental conditions during post hatching migrators allow size strategy that promotes nursery area possible.