Flux of larval fish around Cape Hatteras

Abstract

Convergence of shelf water flows from the Middle and South Atlantic Bights (MAB and SAB) upon Cape Hatteras, North Carolina, presents a potential barrier to the exchange of fish larvae between bights. Impinging water often turns northeastward with the Gulf Stream, and larvae of both cool temperate and warm temperate/subtropical shelf fishes suffer expatriation. Transient oceanographic features exist, however, facilitating shelf retention, cross-bight exchange, and return of expatriated larvae. The impact of these features is mitigated by specific distribution with relation to hydrography, resulting in a selective permeability of this barrier. Dynamic oceanography may result in dynamic recruitment success. We measured the springtime (1996) flux of seven larval fish species assemblages across the confluence by coupling measured water mass/depth specific larval fish concentration with water mass transport values obtained from an extensive moored instrument survey. Strong flows of shallow shelf water from the MAB to the SAB dominated transport of MABspawned larvae even for groups with highest concentrations in waters without strong net flows. Most of these larvae passed from the MAB or the open sea into the study region shelf and from there into the SAB. Net flow of SAB water into the convergence retained SAB-affiliated larvae arriving from the south, but nearshore MAB flows transported low numbers from the MAB to the SAB. The importance of this is tied to the unknown point of introduction of these SAB larvae to MAB waters (e.g., well north of the confluence), but northward exchange of SAB-spawned fish was always prevented along the southern MAB shelf.The flow of shelf water converging upon Cape Hatteras, North Carolina, from the Middle and South Atlantic Bights AcknowledgmentsWe appreciate the involvement of a large number of people integral to the OMP project, including J. Epps, as well as field assistants and sorters J. Hare, N. Craig, K. Roberts, M. Udarbe, H. Neglia, J. Simpson, M. Young, M. Blicktenstein, and others. We benefited from critiques by J. Govoni, R. Cerrato, and two anonymous reviewers.

Anguilliform larvae collected off North Carolina

“…However, this diversity was not reflected in previous larval fish studies in this area (Fahay 1975;Powles and Stender 1976;Powell et al 2000;Marancik et al 2005;Quattrini et al 2005). Explanations for lower numbers of individuals and species in these studies compared with our study may be: (1) relatively more sampling effort at inshore stations in previous studies, (2) sampling at shallower depths even when offshore, (3) relatively more daytime sampling in some previous studies, (4) their use of smaller nets, (5) lack of identification of specimens beyond order or family levels, (6) eels omitted from analyses (Grothues et al 2002). Despite some spatial and temporal limitations, our June to October Gulf Stream collections off North Carolina yielded a substantial proportion (63 species) of the 152 described anguilliform species (14 families) known from the western central Atlantic Ocean (Carpenter 2002).…”

Anguilliform larvae collected off North Carolina

“…However, this diversity was not reflected in previous larval fish studies in this area (Fahay 1975;Powles and Stender 1976;Powell et al 2000;Marancik et al 2005;Quattrini et al 2005). Explanations for lower numbers of individuals and species in these studies compared with our study may be: (1) relatively more sampling effort at inshore stations in previous studies, (2) sampling at shallower depths even when offshore, (3) relatively more daytime sampling in some previous studies, (4) their use of smaller nets, (5) lack of identification of specimens beyond order or family levels, (6) eels omitted from analyses (Grothues et al 2002). Despite some spatial and temporal limitations, our June to October Gulf Stream collections off North Carolina yielded a substantial proportion (63 species) of the 152 described anguilliform species (14 families) known from the western central Atlantic Ocean (Carpenter 2002).…”

Distribution and abundance of beaked whales (Family Ziphiidae) Off Cape Hatteras, North Carolina, U.S.A.

“…, Blake and Hilbig ), and represent a transition and transport zone for larval fishes from the Mid‐Atlantic and South Atlantic Bights (Grothues and Cowan , Grothues et al . ). The results of this study demonstrate that these waters also host extremely high densities of multiple species of beaked whales.…”

Entrainment of larval fish assemblages from the inner shelf into the East Australian Current and into the western Tasman Front

“…, 2011). Similarly, on the northeast US continental shelf, a flux of larval fish is also observed, from north to south, towards Cape Hatteras before entrainment into the Gulf Stream (Grothues and Cowen, 1999; Grothues et al. , 2002).…”

Anguilliform larvae collected off North Carolina

“…However, this diversity was not reflected in previous larval fish studies in this area (Fahay 1975;Powles and Stender 1976;Powell et al 2000;Marancik et al 2005;Quattrini et al 2005). Explanations for lower numbers of individuals and species in these studies compared with our study may be: (1) relatively more sampling effort at inshore stations in previous studies, (2) sampling at shallower depths even when offshore, (3) relatively more daytime sampling in some previous studies, (4) their use of smaller nets, (5) lack of identification of specimens beyond order or family levels, (6) eels omitted from analyses (Grothues et al 2002). Despite some spatial and temporal limitations, our June to October Gulf Stream collections off North Carolina yielded a substantial proportion (63 species) of the 152 described anguilliform species (14 families) known from the western central Atlantic Ocean (Carpenter 2002).…”

Distribution and abundance of beaked whales (Family Ziphiidae) Off Cape Hatteras, North Carolina, U.S.A.

“…, Blake and Hilbig ), and represent a transition and transport zone for larval fishes from the Mid‐Atlantic and South Atlantic Bights (Grothues and Cowan , Grothues et al . ). The results of this study demonstrate that these waters also host extremely high densities of multiple species of beaked whales.…”

Entrainment of larval fish assemblages from the inner shelf into the East Australian Current and into the western Tasman Front

“…, 2011). Similarly, on the northeast US continental shelf, a flux of larval fish is also observed, from north to south, towards Cape Hatteras before entrainment into the Gulf Stream (Grothues and Cowen, 1999; Grothues et al. , 2002).…”

Anguilliform larvae collected off North Carolina

“…However, this diversity was not reflected in previous larval fish studies in this area (Fahay 1975;Powles and Stender 1976;Powell et al 2000;Marancik et al 2005;Quattrini et al 2005). Explanations for lower numbers of individuals and species in these studies compared with our study may be: (1) relatively more sampling effort at inshore stations in previous studies, (2) sampling at shallower depths even when offshore, (3) relatively more daytime sampling in some previous studies, (4) their use of smaller nets, (5) lack of identification of specimens beyond order or family levels, (6) eels omitted from analyses (Grothues et al 2002). Despite some spatial and temporal limitations, our June to October Gulf Stream collections off North Carolina yielded a substantial proportion (63 species) of the 152 described anguilliform species (14 families) known from the western central Atlantic Ocean (Carpenter 2002).…”

Distribution and abundance of beaked whales (Family Ziphiidae) Off Cape Hatteras, North Carolina, U.S.A.

“…, Blake and Hilbig ), and represent a transition and transport zone for larval fishes from the Mid‐Atlantic and South Atlantic Bights (Grothues and Cowan , Grothues et al . ). The results of this study demonstrate that these waters also host extremely high densities of multiple species of beaked whales.…”

Entrainment of larval fish assemblages from the inner shelf into the East Australian Current and into the western Tasman Front

“…, 2011). Similarly, on the northeast US continental shelf, a flux of larval fish is also observed, from north to south, towards Cape Hatteras before entrainment into the Gulf Stream (Grothues and Cowen, 1999; Grothues et al. , 2002).…”