Density-independent factors are also widely believed to be important (e.g., Grossman et al. 2010) in both marine and freshwater environments. In marine fishes, density-independent factors operate largely, though not exclusively, through effects on juvenile survival resulting from a match or mismatch between spawning times and variability in temperature and (or) food (Frank and Leggett 1994; Dingsor et al. 2007). In freshwater fishes, densityindependence operates mainly through broad random fluctuation in the critical environmental variables that control growth, survival, and reproduction throughout the life cycle. In both environments, density-independent factors may also operate indirectly through density-dependent processes to attenuate or amplify the effective action of concurrently operating density-dependent processes (Evans et al. 1990; Power 1997). For example, low rainfall may reduce usable habitat, leading to density-dependent reductions in survival.