MEPS 514:137-148 (2014)  -  DOI: https://doi.org/10.3354/meps10990

ABSTRACT: Freshwater inflows are crucial for the function of estuaries but can become limited in the Mission-Aransas Estuary, Texas, USA, due to drought and human use. Several studies have linked blue crab Callinectes sapidus populations to freshwater inflows, suggesting that inflows may be critical for an early life-history event such as megalopae recruitment through selective tidal stream transport. This study examined whether the salinity response behaviors of C. sapidus megalopae that regulate selective tidal stream transport provide a plausible link between blue crab populations and freshwater inflows in the Mission-Aransas Estuary. The results of behavior experiments indicate that Texas megalopae have more variable responses to rates of salinity change than megalopae in a North Carolina, USA, estuary with higher freshwater inflow and that this variance lies between cohorts. Also, the rate of salinity increase that elicited the maximum behavioral response is half the rate reported in the North Carolina study. A simple behavior-driven flux model shows that this higher sensitivity is adaptive for transport into the Mission-Aransas Estuary when an estuarine gradient is present but not during drought conditions, as export out of the estuary is possible due to increasing salinity on the ebb tide. Transport of megalopae out of the estuary during drought may lead to recruitment failures in the absence of other recruitment mechanisms.

KEY WORDS: Selective tidal stream transport · Blue crabs · Freshwater inflows · Recruitment · Salinity · Drought · Callinectes sapidus · Crustacea · Crustacean larvae