Fisheries Management Plans (FMPs) require the identification and protection of essential fish habitat (EFH). Delineation of EFH is particularly difficult for migratory fish which utilize large expanses of habitat throughout their life history. This study’s main objective was the development and evaluation of habitat assessment tools for the early life stages of American shad (Alosa sapidissima), an anadromous fish managed with a FMP, in two coastal plain rivers of Virginia. To accomplish this, shad spawning and larval nursery habitats were first delineated in the Mattaponi and Pamunkey rivers using presence of eggs and larvae (1997-1999) as evidence of habitat use. Potential interactions of American shad and striped bass, another important fisheries species in these systems, that may affect spawning or survival of progeny were also examined. American shad eggs and larvae were more abundant on the Mattaponi River than the Pamunkey River, while the opposite pattern was apparent for striped bass eggs and larvae. There was overlap between the extreme ranges of spawning of shad and striped bass, but the primary spawning habitat of each species was spatially disjunct in both rivers. Next, habitat suitability index (HSI) models were developed based on extensive literature reviews for hydrographic, physical habitat, shoreline and land use features, which are potential influences on shad production in the Mattaponi and Pamunkey rivers.

A macroscale habitat assessment protocol was developed which was used to separately rate habitat in the rivers based on hydrographic, physical habitat, shoreline and land use parameters. These parameters were also evaluated for associations with American shad eggs and larvae during 1997-1999 collections for corroboration of habitat ratings. Values for parameters used in the ratings were obtained from a variety of sources in attempts to combine best-available data. Data sources consisted of a combination of field assessments, long-term data sets and remote sensing. Multivariate statistical analyses indicate the importance of hydrographic parameters (current velocity, dissolved oxygen and depth); physical habitat features (sediment type and deadfall); and forested shoreline and land use features to presence of eggs. Larvae were more dispersed than eggs and distinct habitat associations could not be discerned. Morphological features indicate the presence of three distinct regions along the Mattaponi and Pamunkey river gradients. Presence of eggs is typically associated with upstream and mid-river regions, while larvae were dispersed amongst the three regions. The combination of remote sensing and on-site data collection and analyses used in this study may be an effective way to rapidly assess fish habitat when data are limited.

Because shad spawning and nursery habitat is thought to fluctuate with abiotic influences, hydrographic factors hypothesized to impact spawning location, transport of larvae, development rates and predator and prey abundance were examined. Utilizing the juvenile Alosa index (JAI) from 1991-1999 as an estimate of juvenile shad recruitment in the Mattaponi and Pamunkey rivers, correlation with hydrographic parameters during the months March-June was examined. Hydrographic conditions during May and June appear to most accurately predict patterns in juvenile recruitment in the Mattaponi River, however trends in the Pamunkey River were not as consistent. Because of the inconsistency in hydrographic controls between rivers, other possible influences were explored, including biotic, morphological, and water quality. Ultimately, discharge affects transport of weak-swimming early larva to variably favorable nursery habitats. A conceptual hydrodynamic model was developed which explores potential impacts of variable habitat exposures on larvae driven by spawning location, habitat suitability, discharge and hatching rates.