The Mid Atlantic Cold Pool and Stock Assessments: Developing Environmental Indices at the Range Limit of Species Environmental conditions have a particularly large influence on population dynamics at the edges of a species' range (Myers 1998, Brander 2007). For example, in a review of environment-recruitment correlations, Myers (1998) found that nearly all the temperature correlations that held-up upon reexamination were associated with populations near the limit of their range. Several studies have now also shown poleward distributional shifts in multiple fisheries species due to a warming climate (Perry et al. 2005, Mueter and Litzow 2008, Nye et al. 2009). These shifts may keep the area occupied by a species constant, but within a given region (e.g., the northeast U.S. shelf ecosystem), may represent a range expansion or contraction. The process explanation for these responses is that at the distributional extremes, temperatures approach the physiological thresholds below (northern end) and above (southern end) which population death rate and emigration exceed population growth rate and immigration.