Eulerian views of layered water currents, vertical distribution of some larval fishes, and inferred advective transport over the continental shelf off North Carolina, USA, in winter

Abstract

Currents that effect the shoreward transport of the larvae of estuarine‐dependent fishes spawned in winter in Onslow Bay, North Carolina, USA, were driven by winds and pressure gradients, and influenced by the Gulf Stream. Aside from storms, winds over the continental shelf in Onslow Bay blew predominantly alongshore with velocities approaching 14 m s‐1 during February and March 1986, and January and February 1989. Water masses and currents observed at two current‐meter moorings, one at mid‐shelf and the other on the outer shelf, reflected the onshore (or offshore) advection of interior water in compensation for the offshore (or onshore) advection of wind‐driven surface water. Winds and currents reversed direction approximately every 4 to 6 days. The larvae of Atlantic menhaden, Brevoortia tyrannus, spot, Leiostomus xan‐thurus, and Atlantic croaker, Micropogonias undulatus, were most abundant in 17–19oC and 20–21oC water of the outer shelf and Gulf Stream fronts. There was little indication of diel vertical migration; larval Atlantic menhaden were most abundant in mid‐ and surface water, while spot and Atlantic croaker were most abundant in mid‐ and deep water. Given this distribution, the inferred advective transport of larvae was at times onshore, but at other times it was offshore. Within a spawning season, the prevalence of either reciprocation could determine the number of larvae that reach coastal inlets.

Displacement of diverse ichthyoplankton assemblages by a coastal upwelling event on the Sydney shelf

“…We could not, however, identify mesopelagic taxa to species. Local notosudids and melamphaeids are probably each represented by a single species (Scopelosaurus meadi and Melanlphaes sp., Gomon et al 1994) and are some of the few abundant, deeply distributed taxa. Myctophidae is a speciose family, but is a useful tracer of oceanic water at this taxonomic level (Cowen et al 1993).…”

Coastal fish farms are settlement sites for juvenile fish

“…Settlement and recruitment of fish to nursery habitats may be determined by a combination of several factors, such as spawning strategies of breeding stocks (Sherman et al 1984), chemical cues (Sweatman, 1988), or oceanographic features (Govoni and Pietrafesa, 1994), amongst others. Despite considerable research, factors leading to habitat choice by pre-settlement fish remain unclear.…”

Wind effect as forcing factor controlling distribution and diversity of copepods in a shallow temperate estuary (Solis Grande, Uruguay)

“…Relations between plankton and environment in estuarine areas have been studied by several authors, by analyzing the distribution of species in relation to horizontal and vertical environmental gradients (Maurer et al, 1978;Collins and Williams, 1982;Stearns et al, 1989;Hough and Naylor, 1991;Madariaga et al, 1992;Dodson, 1993, 1994). More recently the effect of wind on fish larvae (Govoni and Pietrafesa, 1994) and on dispersal dynamics of postlarval macrofauna of benthic systems (Commito, 1995) was introduced in models as an explanatory variable.…”