Tropical storm and environmental forcing on regional blue crab (Callinectes sapidus) settlement
Global climate change is predicted to increase the frequency and magnitude of hurricanes, typhoons and other extreme cyclonic disturbance events, with little known consequences for recruitment dynamics of marine species that rely on wind-driven larval transport to coastal settlement and nursery habitats. We conducted a large-scale settlement study of the blue crab (Callinectes sapidus) in the Croatan-Albemarle-Pamlico Estuarine System (CAPES) in North Carolina, the second largest estuary in the US, during a 10-yr period that encompassed 35 tropical storms of varying magnitudes and tracks, to determine the effects of hurricane track, wind speed and direction as well as lunar-associated explanatory variables on spatiotemporal variation in settlement. The results suggest that much of the spatiotemporal variation in blue crab settlement within the CAPES is due to a combination of: (i) stochastic, meteorological events such as the number of tropical storm days during the fall recruitment season (∼28% of the monthly variation explained), (ii) the frequency and duration of wind events blowing toward the southwest and, to a lesser degree, (iii) periodic events such as hours of dark flood tide. Tropical storms and hurricanes expand the blue crab nursery capacity of the CAPES. The benefits of hurricane-forcing to megalopal settlement was dependent upon the storm track, with highest settlement events generally associated with ‘onshore’ storm tracks that made landfall from the ocean and moved inland along a southeasterly/northwesterly path, or ‘coastal’ storms that followed a path roughly parallel to the coastline and were located <300 km offshore of the coast.