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In the complex web of environmental variables to which fish respond, regional climate is perhaps the least well understood and probably the least studied. There are documented correlations among both fish abundances and distributions and climate signals, but most studies concern fish populations in open‐ocean settings such as the North Sea, the Bering Sea, the Northeast Atlantic and the Northwest Pacific (e.g., Brander 2007; Brunel and Boucher 2007). Recently, however, there has been a focus on the effects of climate change on coastal fish populations in the eastern United States. For example, Condron et al. (2005) found that the abundance of North American Atlantic salmon Salmo salar fluctuates with a sea surface temperature–based climate index reflecting the Atlantic Multidecadal Oscillation (AMO). They concluded that continued warming near the Grand Banks of Newfoundland will negatively impact the already depleted salmon stock regardless of the reduction in commercial fishing. Similarly, Hare and Able (2007) found that large‐scale variability in the abundance of Atlantic croaker Micropogonias undulatus along the East Coast of the United States is also driven by climatic processes, with increases in abundance or larger year‐classes being correlated with the warm winters associated with the positive phase of the North Atlantic Oscillation (NAO; Hurrell et al. 2003).
The effects of climate are not linear, and complex relationships between climate indices and abiotic factors such as discharge and streamflow have been identified in some aquatic systems in the eastern United States. Specifically, the AMO has been linked to rainfall and streamflow variability in Florida, with the inflow to Lake Okeechobee varying by 40% between the warm and cool phases of the oscillation (Enfield et al. 2001). Similarly, Bradbury et al. (2002) found that the NAO and the Pacific North American oscillation are positively correlated with streamflow variability in several New England streams. Lastly, much evidence suggests that fish abundances and distributions are affected by streamflow (Poff and Ward 1989; Puckridge et al. 1998; Juanes et al. 2004; Doyle et al. 2005; Gillette et al. 2006).
The Hudson River estuary (HRE) fish community is ideal for testing how local hydrology (e.g., water temperature and streamflow) and regional climate influence fish abundance patterns over time. It...