Biophysical dynamcs of larval fish ingress into Chesapeake and Delaware Bays.

摘要

Transport of early life stage fishes is controlled by complex physical processes interacting with trophodynamic responses to those processes. Identifying biophysical dynamics of larval ingress to estuaries is critical for understanding recruitment dynamics. Within this dissertation, I measured ingress patterns of four species of early stage fishes: Atlantic menhaden (Brevoortia tyrannus), Atlantic croaker (Micropogonias undulatus), glass eel stage American eel (Anguilla rostrata) and summer flounder (Paralichthys dentatus) at two locations (Roosevelt Inlet, DE and York River, VA) over three years (2007-2010). I analyzed how observed wind patterns enhanced larval transport for each species/location with weekly ichthyoplankton ingress samples, during peak ingress events and using time series analyses. I evaluated how vertical distributions of Atlantic croaker and Atlantic menhaden vary in Delaware Bay to determine potential vertical migratory behaviors. Also, I have used a larval transport model to simulate transport within Delaware Bay in an effort to understand how winds and larval behavior affect ingress. I found larval fish ingress varies greatly and is species-specific in the way physical and biological processes affect transport. I found empirical relationships between ingress and winds are difficult to characterize consistently. I suggest Atlantic menhaden are primarily driven into Delaware Bay via physical processes including tidal forcing, wind driven forcing and residual bottom layer inflow, as concentrations were vertically similar between depths. In contrast, the ingress of Atlantic croaker is primarily driven by bottom layer inflow as bottom layer concentrations were significantly greater than surface concentrations in Delaware Bay. Model results indicate significant effects of alongshore/along-estuary winds and behavior acted on particle transport into Delaware Bay. Model results agreed with empirical observations of peak ingress events of Atlantic menhaden and Atlantic croaker suggesting wind driven mechanisms enhance ingress. I have demonstrated that species-specific vertical migratory strategies influence how alongshore/along-estuary winds affect transport into an estuary.