Evidence of Life Cycle Diversity of River Herring in the Penobscot River Estuary, Maine

Abstract

Alewife Alosa pseudoharengus and Blueback Herring A. aestivalis—collectively referred to as river herring—exhibit complex life histories, exploiting freshwater and marine biomes to complete their life cycles. We investigated distribution patterns of river herring in the Penobscot River estuary, Maine, USA, from April through September in 2012 and 2013 and found both species in relatively low-salinity portions of the estuary in all months sampled. River herring made up the majority of samples in terms of abundance and biomass for most months. We developed age–length keys for monthly catches and found consistent presence of age-1 and age-2 river herring, especially during spring. We found seasonal patterns in age distribution with age-1 fish and older most abundant in spring and summer and age-0 fish only occurring in late summer through fall. These observations provide direct evidence of life cycle diversity for juvenile river herring, complementing other recent observations in other parts of their native range. Lastly, our findings suggest further consideration should be given to the importance of connectivity between marine, estuarine, and freshwater habitats for age-1 and age-2 river herring and to the more complex ecological roles of age-1 and age-2 river herring given their intermediate trophic level and presence in relatively fresh components of the Penobscot River estuary.