Oyster farming along lower Delaware Bay New Jersey, USA is growing with a rising public demand and readily available disease resistant oysters. The region is also an important migratory stopover site for the rufa red knot, a threatened shorebird, during its spring migration from wintering grounds in Argentina to breeding grounds in the Canadian Artic. The recent federal listing of the rufared knot subspecies has triggered the implementation of regulatory protections that may negatively affect the oyster culture industry in Delaware Bay. Currently, understanding of the potential impacts of oyster cultivation activities on red knot foraging is lacking. This study was designed to gather preliminary data to assess how oyster aquaculture activities affect red knot foraging and habitat use. Along an approximately 3-mile stretch of the Delaware Bayshore, we conducted a census of all accessible portions of the study area and recorded the locations and total number of shorebirds present. We also recorded data on a suite of environmental and behavioral variables thought to influence red knot presence, including the presence of aquaculture structures and oyster tending activities. Using a Bayesian statistical approach, we developed and ranked a set of candidate regression models examining the factors most significantly contributing to red knot abundance.
Our analysis demonstrates that rising and high tides have a significant positive influence on red knot abundance with effect sizes of 2.20 (95%CI: 1.21, 2.23) and 5.38 (95%CI: 4.31, 5.37), respectively. In contrast, falling tide (-9.91, 95% CI: -11.45, -9.84) and oyster tending (-2.26, 95% CI: -5.44, -2.58) have a negative impact. Additional data in the next 2 years should increase the precision of estimated effect sizes and advance the development of red knot protections while facilitating the search for effective solutions in resolving potential conflicts between economic growth and biological conservation along the Delaware Bayshore.