Juvenile atlantic menhaden ( Brevoortia tyrannus) in Delaware Bay, USA are the result of local and long-distance recruitment

Abstract

We examined patterns of abundance, age, and spawning date distribution for juvenile Atlantic menhaden, Brevoortia tyrannus, collected during monthly sampling in Delaware Bay salt marshes during 1996 and 1997 in order to determine temporal patterns of recruitment and their spawning locations. Two distinct cohorts were present during both years of the study; the first cohort appeared in April–May and persisted throughout the summer, while the second cohort appeared in July but was only represented in subsequent collections during 1997. Back-calculated birth dates indicated that some fish had spawned during the fall (September and October) during both years, probably in the vicinity of Delaware Bay. However, the majority of individuals were spawned during winter months (primarily December and January) when water temperatures were too cold to permit local spawning. These winter-spawned individuals probably originated south of Cape Hatteras where winter water temperatures are warm enough (>16 °C) to allow spawning and larval development. These winter-spawned fish were an important but variable fraction of the fish surviving to the juvenile stage in Delaware Bay fish (92 and 73% during 1996 and 1997, respectively). The pattern of fall and winter-spawned juvenile Atlantic menhaden using Delaware Bay is consistent with an earlier study of larval Atlantic menhaden in another southern New Jersey estuary and thus suggests that contributions of spawning from both the Middle Atlantic States and south of Cape Hatteras may occur consistently for Atlantic menhaden and other species.