Daily Patterns of River Herring ( <i>Alosa</i> spp.) Spawning Migrations: Environmental Drivers and Variation among Coastal Streams in Massachusetts

The timing of life history events in many plants and animals depends on the seasonal fluctuations specific environmental conditions. Climate change is altering regimes disrupting natural cycles patterns across communities. Anadromous fishes that migrate between marine freshwater habitats to spawn are particularly sensitive shifting conditions thus vulnerable effects climate change. However, for anadromous fish species mechanisms driving migration spawning not well understood. In this study, we investigated upstream migrations river herring Alosa spp. 12 coastal Massachusetts streams. By analyzing long-term data sets (8–28 years) daily counts, determined local influence factors compared run dynamics among Our results suggest water temperature was most consistent predictor both presence–absence abundance during migration. We found inconsistent streamflow lunar phase, likely due anthropogenic manipulation flow connectivity different systems. Geographic thermal more northerly runs region relatively occurring later spring season, at warmer temperatures approach maxima, a narrower temporal window southern runs. phenology their reliance indicate populations these may benefit from management practices reduce within-stream manipulations maintain coolwater refugia.