Abstract

Invasive species cause extensive ecological damage in freshwater and marine habitats and are a threat to biodiversity in aquatic ecosystems world-wide. One such species, the Chinese mitten crab, Eriocheir sinensis, has invasive populations in northern Europe and San Francisco Bay, and there are confirmed reports of breeding female crabs in both the Chesapeake and Delaware Bays. Despite their threat to these ecosystems, there are still large gaps in the current understanding of this species' larval biology that are critical to predicting the potential for large populations to establish in East Coast bays and estuaries. We addressed these issues by using a physical circulation model of Delaware Bay and the adjacent coastal ocean coupled to a modified particle advection scheme. We used this model to examine the effects of different physical mechanisms and larval behavior on transport, retention, and settlement of larvae in the bay. The circulation model produced flow fields using observed winds and river discharge for 2006 as well as systematic variations of river discharge and wind direction. Since little is known regarding mitten crab larval behavior, the larval component was purposefully general and incorporated a suite of behaviors such as tidal, diel, and ontogenetic vertical migration; however, results of this study showed that vertical migration affects the magnitude, but not locations of larval settlement. Simulations revealed that changes in the time and location of spawning can result in large variations in retention and settlement of larvae in Delaware Bay and the coastal ocean, due to seasonal variations of the physical flow field. Overall results of our study showed that the estuarine and coastal circulation typically found along the Middle Atlantic coast of the United States can result in significant retention of new and established E. sinensis populations in large estuaries as well as transport of larvae to new coastal locations.

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