The Laurentian Great Lakes have been fished with gradually increasing intensity for about 150 years. Their fish communities have been stressed by a broadening variety of other cultural influences besides fishing. A series of recent analyses have identified and distinguished effects due to fishing from those due to other cultural stresses. These analyses are here carried a step further, showing the fishing-up and overfishing sequence, through time, of various species as a function of their economic value to the fishermen. Some elements of a theory are proposed that interrelate a number of whole-system variables; if elaborated further such a theory should be useful in modelling and managing competing fisheries that harvest a number of ecologically interrelated species, perhaps more or less indiscriminately. Further, the theory should permit modelling and managing of other cultural stresses on the fish community, such as nutrient loading and toxic pollution that may act contemporaneously with fishing.