A time series of American eel Anguilla rostrata glass eel abundance, timing and size from Little Egg Inlet, New Jersey (16 years) and Beaufort Inlet, North Carolina (18 years) was used to provide a better understanding of ingress patterns at two, U.S. east coast estuaries. There was no evidence of synchronous declines in abundance between the two locations; however, at the Little Egg Inlet site, glass eels arrived later in the season and at significantly smaller sizes over the duration of the series. One significant linkage between sites was revealed: abundance was positively correlated with winter precipitation. Precipitation differed between sites annually and was correlated with El Nin˜o at Beaufort Inlet and, to a lesser extent, the North Atlantic Oscillation at Little Egg Inlet. It is hypothesized that glass eels may use freshwater signals to enhance recruitment to local estuaries, thus influencing year-class strength, yet the relationship between year-class strength and adult abundance remains unresolved.

The objective of this study was to quantify spatial and temporal variability of anguillid glass eel ingress within and between adjacent watersheds in order to help illuminate the mechanisms moderating annual recruitment. Because single fixed locations are often used to assess annual recruitment, the intra-annual dynamics of ingress across multiple sites often remains unresolved. To address this question, plankton nets and eel collectors were deployed weekly to synoptically quantify early stage Anguilla rostrata abundance at 12 sites across two New Jersey estuaries over an ingress season. Numbers of early-stage glass eels collected at the inlet mouths were moderately variable within and between estuaries over time and showed evidence for weak lunar phase and water temperature correlations. The relative condition of glass eels, although highly variable, declined significantly over the ingress season and indicated a tendency for lower condition A. rostrata to colonize sites in the lower estuary. Accumulations of glass eels and early-stage elvers retrieved from collectors (one to >1500 A. rostrata per collector) at lower estuary sites were highly variable over time, producing only weak correlations between estuaries. By way of contrast, development into late-stage elvers, coupled with the large-scale colonization of up-river sites, was highly synchronized between and within estuaries and contingent on water temperatures reaching c. 10-12 degrees C. Averaged over the ingress season, abundance estimates were remarkably consistent between paired sites across estuaries, indicating a low degree of interestuary variability. Within an estuary, however, abundance estimates varied considerably depending on location. These results and methodology have important implications for the planning and interpretation of early-stage anguillid eel surveys as well as the understanding of the dynamic nature of ingress and the spatial scales over which recruitment varies.

We investigated the relationship between large-scale climate variability (the North Atlantic Oscillation, NAO), continental shelf hydrography, and year-class strength of yellowtail flounder (Limanda ferruginea) in the Middle Atlantic Bight. Using long-term environmental time series , dominant winter NAO phase in the northeast region of the United States was correlated with local air temperature records from Block Island, Rhode Island (December-March). Air temperature also influenced the characteristics of a pool of remnant winter cold water on the continental shelf, such that negative NAO winters produced a colder-than-average summer cold pool, and vice versa.Smoothed data sets of L. ferruginea recruitment over the 36-yr period (using Southern New England VPA and hindcast data) were highly correlated with the NAO and air temperature, highlighting the influence of multi-year variability. Although less robust, the relationship with the NAO remained significant after removing equal-but-opposite long-term linear trends from the series. Surprisingly, recruitment and cold pool bottom temperature were only marginally correlated. Data from independent 2-m beam trawl and submersible sampling in the region (1994,(1996)(1997)(1998)(1999)(2000) indicated a strong relationship between the abundance of recent settlers and cold pool temperature; however, this pattern was often modified by subsequent changes in cold pool stratification (fall overturn). These results underscore the dynamic role thermal habitats play in the lives of early stage benthic fishes. For yellowtail flounder, the generation of recruitment variability represents one endpoint of a complex interaction between large-scale phenomena (climate) and more localized, event-scale features (cold pool).

With the recent decline of several exploited populations of northwest Atlantic fishes, effort has been directed toward understanding the scales at which recruitment varies along with the deterministic processes underlying this variability. Using surveys from 3 research submersible cruises (1994, 1997, 1998), we examined the distributions of 4 species of recently settled groundfish in relation to spatial scale on the New York Bight region of the continental shelf (USA). A hierarchical sampling design was used to calculate the percent variability in abundance partitioned over 4 nested scales: submersible transect (~100 m), site (~10 km), shelf zone (~25 km), and sampling line (~100 km). For all years, early juveniles of Limanda ferruginea (yellowtail flounder) were highly concentrated at the shelf-zone scale, where abundance followed the thermal contours of a mid-shelf cold pool of remnant winter water. Conversely, Hippoglossina oblonga (fourspot flounder) and Citharichthys arctifrons (Gulf Stream flounder) were highly site-dependent, bounding the distribution of L. ferruginea at inner and outer shelf sites, respectively. Merluccius bilinearis (silver hake) exhibited moderate to high variability partitioned over several scales. For all species, the absence of sampling-line variability suggested that settlement patterns were consistent across the breadth of the shelf, while substantial residual variance suggested that microscale-level processes generated additional variability. Annual settlement of these early juveniles is highly specialized and cued to distinct aspects of the physical and biological setting of the New York Bight. Conceptually, these local habitat parameters can be used to link nodes of high variability with the possible deterministic processes modifying recruitment. Our results underscore the critical contribution juvenile nursery habitats may have to the subsequent survival and growth of continental shelf species.

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