Dynamically Linking Marine Zooplankton, Fishes and Environmental Variables in the George Bank Ecosystem

The population dynamics of marine fishes are related to environmental and lower trophic level processes.  Understanding inter-relationships among exploited fish populations, their prey resources and environmental forcing will be a critical step in moving toward Ecosystem-Based Fishery Management.  To address these issues we focused on marine zooplankton, key pelagic and demersal fish populations (Atlantic herring, Atlantic mackerel, haddock and Atlantic cod) and environmental variables (e.g. AMO, NAO, SST, wind stress, stratification) on George Bank during the period from 1977 to 2008.  We conducted multivariate nonlinear time series analysis to quantify the underlying dynamical complexity (i.e. nonlinearity, dimensionality) of marine copepods, selected fish populations and environmental variables.  Further, we examined dynamical connections (co-predictability) among them.  Preliminary findings show that environmental variables and marine copepods both tend to exhibit linear dynamics.  In contrast, low-dimensional and weakly nonlinear dynamics were identified for the fish populations examined.  Moreover, significant dynamical connections were found among fishes, copepods and environmental variables.  We explored the dynamical features of marine zooplankton and environmental variability in terms of the dynamics of marine fish populations in this well-studied system.