Time and time again studies point out that the biggest factor faced in a fishery is limited food supply. That can occur many ways some noted in this thread. It can be size , timing , type or cyclical or other events which cause the problem. They usually lead to imbalance which is the normal status in most waters ( they go from unbalanced one direction to unbalanced the other direction). This type of event is especially common with GS. It is exacerbated both by their cyclical spawning , cold intolerance up north and the tendency to take up too much of the biomass capacity at any size structure of GS. There can be too many 2 inch or too many 15 inch GS or even too many of all sizes. Their interaction with other species is varied depending on the situation at that time but it all most always ends in a population imbalance of some nature. you can use them to manage for a specific goal but it is not an easy path. I don't know of many who want 60+ % of their biomass (carrying capacity) tied up in GS with the other species in an imbalanced pond (see your lake for example). See pic below of northern GS.
Gizzard Shad (up north)
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