Trophic transfer in seagrass systems: estimating seasonal production of an abundant seagrass fish, Bairdiella chrysoura, in lower Chesapeake Bay

Silver perch Bairdiella chrysoura is a seasonally abundant fish in lower Chesapeake Bay seagrass habitats. Young-of-the-year fish recruit to these habitats in June and rear for the remainder of the summer before migrating to deeper habitats in the Bay and offshore as seawater cools in the fall. This species has been shown to be abundant in seagrass habitats, yet like many fishes in these habitats, little is known about its growth and production, and thus the contribution of this habitat type to overall production. We developed a bioenergetics model to estimate individual silver perch growth and calibrated this model using field-collected size data. Abundance data were used to develop a generalized additive model for predicting abundance over the simulation period (15 June to 15 October). We used the individual-based model output and estimated abundances to calculate total production. The calibrated bioenergetics model showed silver perch growth of approximately 0.19 g d(-1) for total growth of 23.2 g over the simulation period. Peak abundance occurred in July with estimated values of 0.2 ind. m(-2). The highest biomass was observed shortly after peak abundance. Total production for silver perch was estimated to be 22.9 g m(-2) in the seagrass habitats measured. With an estimated 8100 ha of seagrass habitat in the lower Chesapeake Bay in 2010, silver perch contribute a considerable amount of biomass production. As an annually migrating species, silver perch export in excess of 7400 t of biomass to the near-coastal ecosystem, providing a trophic subsidy from seagrass habitats via trophic transfer.