TABLE 1 Summary of life-history aspects and behavior in the marine environment for each alewife (Alosa pseudoharengus), blueback (Alosa aestivalis), and American shad (Alosa sapidissima). AspectAlewifeBlueback herringAmerican shadLife historyDietMainly prey on non-decapod crustaceansConsume both pelagic and benthic prey, but more selective than alewifeAdults cannibalize juveniles in nearshore areas on their migration back to seaAdults also feed on copepods and krillLarger individuals (> 20 cm) feed on mollusks,Juveniles primarily feed on zooplanktonAt sea, adults feed on copepods, mysids, and small fishcnidarians, and bony fishAdults also consume zooplankton, as well as small fishes, fish eggs, and small crustaceansGrowthEvidence of 114 – 127 mm of growth in their first year in the Chesapeake Bay estuaryAdults grow up to 197 – 322 mm in fork lengthJuveniles migrate to sea when they reach 38 – 114 mmFemales are larger than males; 289 mm and 277 mm, respectivelyShad are larger than alewife and blueback and reach up toAdults are sexually dimorphic; females spend longer at sea and reach a larger average length of 284.3 mm, whereas males average 271.6 mm760 mmGrowth rates plateau after spawning, and there is little growth between spawning eventsFemales are larger than malesNorthern populations are larger than southern contingentsMaturation at sea takes 3 – 6 yearsEnergetic trade-off between frequent spawning and at-sea growth (multiple spawners are smaller)Maturation at sea takes 2 – 6 years; males typically mature in 2 years, females mature in 3 – 4 yearsLower latitude populations are shorter lived and quicker to matureAverage VBGF growth parameters:VBGF growth parameters:Maturation at sea takes 4 – 5 years for females and 3 – 4 years for malesL ∞ = 481 mmL ∞ = 291.67 mm (males) – 310.48 mm (females)K = 0.44VBGF growth parameters:t 0 = 0.32K = 0.4 (females) – 0.441 (males)L ∞ = 231.33 mm (males) – 259.85 mm (females)t 0 = 0.103 (females) – 0.142 (males)K = 0.469 (females) – 0.590 (males)t 0 = 0.283 (females) – 0.338 (0.338)SpawningAdults exhibit spawning site fidelity and return to their natal stream or pond using olfactory cuesAdults return to their natal river to spawnAdults exhibit spawning site fidelity and return to their natal river to spawn; low levels (3%) of straying have been observedExhibit iteroparity and will spawn up to four timesHigher-latitude populations demonstrate more frequent iteroparityNorthern populations are iteroparous and can spawn up to five to seven times, whereas the southern populations are semelparousGravimetric fecundity positively correlates with age and decreases with increasing latitudeInterannual returns are higher among malesPrecede blueblack in spawning migrations of shared riversSpawning season lengthens with increasing latitudeSemelparity is observed only in St. Johns River, Florida, and Ogeechee River, GeorgiaSpawning can take place in brackish waterReturn to spawn later in the spring than alewifeMortalityLower-latitude populations live 3 – 4 years; northern counterparts live up to 9 – 10 yearsMaximum age of an individual observed in sampling studies were 8 and 12 years oldCan live up to 13 yearsNatural mortality rates differ based on latitude due to reproductive styles; northern populations live longerPredation is a primary cause of mortalityFemales live longer than malesEnergy movement and nutrient input in the marine environment are understudied but likely comparable to the contributions in fresh waterMales are more abundant in younger age classesPredation by sharks, several fish species, and marine mammals significantly contribute to adult mortalityPredation by fish, sea birds, and marine mammals is a leading cause of mortality in the marine environmentAdults commonly die during spawning migrationsKey driver of predator movement (i.e., Atlantic codand other gadids)BehaviorMigrationRange from Carolina to NewfoundlandMarine range from Florida to Nova ScotiaMigrate from Florida to NewfoundlandJuveniles join large schools of similar-sized individuals after they leave their spawning riverSome migratory contingents remain resident in estuaries near spawning rivers; some undertake offshore migrationsIntraspecific schools of juveniles and postspawning adults overwinter in deep waters offshore Florida, the Mid-Atlantic Bight, and along the Scotian ShelfSchooling with menhaden or blueback is commonMove northward and inshore in the spring and offshore and southward in the fallSummer aggregations consist of a mixed stock of contingents from multiple riversOverwintering aggregations are heterogenous mixtures of populations from many riversFound along the Mid-Atlantic coastline in the winter and springMove southward in the fall to aggregate offshore in deeper waters in overwintering sites in Mid-Atlantic Bight and along Scotian ShelfSpawning migrations occur when water temperatures are between 8 and 26 CMovement is regulated by zooplankton productivity and by abiotic factors, such as temperature, tidal currents, salinity, and depthSouthern populations begin northward spawning migrations in January, and northern populations begin spawning migrations progressively later into the spring as latitude increasesMigration follows temperature contours in northern limit of range and zooplankton availabilityMarine temperatures> 14 C are avoidedWater temperatures 5 – 10 C cue spawning migrationsMove to mid-depth, coastal waters in the springMigration to spawning rivers when water temperatures range 14 – 22 CSpawning begins late March in the south and progressively later into July further northSpawning begins later than blueback herring, in late AprilForagingUse a mixture of inshore and offshore foraging areasSchool as single-species aggregations or with alewife to optimize feedingJuveniles join large intraspecific feeding schools along the coastDemonstrate diel feeding patterns following zooplanktonFeeding schools are mixed stock of several populationsUndertake diel vertical migrations following zooplankton throughout water columnPrimarily feed in the eveningSummer foraging grounds include surface waters in the inner Bay of Fundy, the inner Gulf of St. Lawrence, and off Newfoundland and LabradorHave diel vertical migrations following zooplanktonDemonstrate active foraging and filter-feedingFeeding migrations from North Carolina to Nova Scotia have been recordedUse both particulate (during day) and filter-feeding (during night) strategiesMajority of foraging occurs in the marine environmentSome populations utilize inshore embayments for feeding in the summerAdults demonstrate passive filter feeding and active foragingZooplankton productivity and foraging partially regulate movement at seaForage in nearshore habitat until water is too warm (>14 C) Abbreviation: VBGF, von Bertalanffy growth function.

Published as part of Brown, Caliyena R., Sergio, Ava J. A., Bate, Caitlin S., Koopman, Natalie, Roland, Joshua B., Notman-Grobler, Oscar D. P., Mastrodimitropoulos, Paris M. B., Piczak, Morgan L. & Lennox, Robert J., 2025, A review of migratory Alosidae marine ecology in the northwest Atlantic, pp. 680-681 in Journal of Fish Biology 106 (3) on page 680, DOI: 10.1111/jfb.15977, http://zenodo.org/record/17003533