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~ temperature and oxygen due to flow alterations within a factor of two. This level requires limited field studies and textbook level analysis of the fate of pollutants such as heat, oxygen demand, solids, etc; (3) level three will expand the set of chemicals to be analyzed and attempt to employ state-of-the-art technology. This level requires extensive field observations and mathematical mOdeling to predict time-dependent fluctuation in heat and chemical concentrations in a reach; (4) level four involves research and development concepts that attempt to improve the current state of knowledge of the fate of toxic pollutants and to define chronic exposure levels that impact the aquatic ecosystem. This level will seek to add to scientific understanding as the first priority, and will complicate rather than clarify most management decisions. This module's report concludes with examples of methodologies for each proposed level of analysis. The workshop on instream fishery ecosystems concentrated on a critique of the incremental methodology as it pertains to fish, both as a concept and as an analytical approach, Two major criticisms were made: (1) the methodology is not a consistent system of strongly interacting components, but a collection of specific modules interrelated by stream hydraulics; and (2) the methodology is based on a narrow set of physical parameters providing necessary, but not sufficient, conditions for the suitability of stream habitats, The workshop proposed the development of an ecosystem holistic viewpoint by IFG to overcome the two major criticisms. The methodology now used should be expanded to include parameters that reflect chemical and biological processes of ecosystems. Recommended parameters, in order of importance, are. (a) depth; (b) velocity; (c) temperature; Cd) food supply; (e) riparian cover, ~ ~ ~ 19 ~