A review of migratory Alosidae marine ecology in the northwest Atlantic

Abstract

Migratory animals play a crucial role in connecting distinct habitats by transferring matter and energy across ecosystem boundaries. In the North Atlantic, anadromous species exemplify this through their movement between freshwater and marine environments. Alosids, including species such as alewife (Alosa pseudoharengus), blueback herring (Alosa aestivalis), and American shad (Alosa sapidissima), exhibit this migratory behavior to maximize growth and fecundity and are, therefore, vital components of Atlantic coastal ecosystems. Despite their ecological importance, these species have experienced considerable population declines. Due to a research focus on dams and the freshwater phase of their ecology, the marine ecology of Alosids remains much less understood, potentially hindering effective management. This paper synthesizes current knowledge on the marine ecology of anadromous alewife, blueback herring, and American shad in the northwest Atlantic, focusing on life-history aspects, migratory patterns, and foraging behavior at sea. The paper also outlines current fisheries management and the anthropogenic threats these species face during their marine phase. We identified knowledge gaps regarding marine distribution, migration routes, impacts of climate change on movement and behavior, population dynamics, and the identification of gaspereau. By identifying gaps in the literature, we highlight research needs, emphasizing the role of telemetry studies in tracking marine movements and the impact of climate change on habitat use. Addressing these gaps through targeted research on marine ecology and movement patterns is essential for developing informed management strategies aimed at increasing Alosid populations.

Keywords: anadromous; conservation; fisheries management; forage fish; migration; movement ecology.

FIGURE 1

(a) Alewife and blueback herring (photo credit: Christopher Bartlett) and (b) American shad (photo credit: Mikey Lennox).

FIGURE 2

Threats facing diadromous Alosids, including alewife, blueback herring, and American shad in marine environments. (a) commercial fisheries, (b) habitat degradation, (c) by‐catch in Atlantic mackerel and Atlantic herring commercial fisheries, (d) global climate change, and (e) misidentification and hybridization of alewife and blueback herring (collectively known as gaspereau and river herring; photo credit: [a]–[d] Canva, [e] Christopher Bartlett).