A Meta-Analysis of the Habitat Carrying Capacity and Maximum Reproductive Rate of Anadromous Alewife in Eastern North America

—We analyzed the dynamics of eight populations of anadromous alewife Alosa pseudoharengus to determine their habitat carrying capacity, their maximum reproductive rate, and whether depensation occurs at low abundances. When spawner–recruit models are fit to data sets for individual alewife populations, the resulting parameter estimates are often poorly determined, biologically unrealistic, and highly variable among populations. When the spawner and recruit time series for all populations are standardized to the same scale, populations that are outliers and appear to be at low levels are immediately evident. We also used nonlinear mixed-effects models to estimate spawner–recruit parameters for the eight populations simultaneously. By assuming that the maximum reproductive rate and carrying capacity per unit area are random variables drawn from probability distributions that are characteristic of the species, among-population variability is greatly reduced, and the parameter estimates resulting from the mixed-effects model are biologically reasonable. While the maximum reproductive rate, which can be interpreted as the biological limit for anthropogenic mortality, shows little variability among populations, the carrying capacity per unit area varies by more than an order of magnitude among populations of this species. We did not find evidence of depensation in the eight populations examined.