ABSTRACT
Fluctuations in fish stock abundance are caused by fishing, modification of population-dynamic stabilizing mechanisms, and changes in the physical environment. The magnitude of each cause, in any particular case, is difficult to assess. The difficulty lies in the highly-dimensional "environment" and in the nonlinear population-dynamics response. Because of these facts, empirical correlations are difficult to interpret. While "spurious correlation" is well known, some correlations may appear spurious, even when they are not. To circumvent the difficulty, it is necessary to understand the relationship between the population-dynamics process and the physical environment at the most fundamental level. This chapter describes aspects of this interaction at the basin and microscale levels.
