Measures of fish body condition are often used to summarize the health or fitness of a population (or individuals within) at a point in time. These measures can be used as indicators of natural fluctuations by fish in response to their environment or to management outcomes, such as from environmental water delivery. Indicators of body condition can then be used to predict future population outcomes such as spawning and recruitment based upon the linkage between higher energy stores being translated into benefits for offspring. Hence, fish body condition may be used as a tool to represent the intermediate step between a management intervention (e.g. environmental flow) and an ultimate target (e.g. population growth). This assumes that increased body condition will directly result in increased reproductive gains. However, even an increase in body condition may still be insufficient to lead to oogenesis or spermatogenesis due to a range of environmental or physiological constraints. This presentation will examine two specific aims. First, can indirect measures of body condition (e.g. length-weight indices) represent direct measures (e.g. tissue lipid content) consistently through time if at all? Second, can measures of body condition (direct or indirect) be used to predict positive population outcomes? This research ultimately examines the influence of body condition on both GSI and juvenile recruitment in two generalist species (golden perch and bony bream) in a lowland river.