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<br />and (f) competition, Additional factors of less importance (unranked) <br />include: (g) predation; (h) substrate; (i) dissolved oxygen; (j) instream <br />cover; (k) nutrients; (1) stream morphology; and (m) sediment load, <br />The following avenues for improvement or expansion of the incremental <br />methodology were identified: (1) an alternative to weighted usable area <br />should be sought for use in simulation of stream flow phenomena; (2) the <br />choice of modules in the hierarchical modular approach should be reevaluated <br />and the modules developed with different data requirements for different <br />resolution levels; (3) parameters to establish necessary and sufficient <br />conditions for fish habitats need to be more fully identified; (4) ecological <br />simulation should be incorporated into the IFG models; (5) both intensive and <br />extensive validation of the methodology should be sought. (For example, <br />intensive testing should be undertaken in regions where large data bases <br />exist, such as salmonid streams of the Pacific northwest. Extensive testing <br />should cover a range of physiographic provinces, i.e" comparing studies of <br />eastern salmonid streams with western results, then extending to main stream <br />rivers and non-salmonid species); (6) documentation of stream ecology over a <br />broad spectrum of stream types and regions should be stressed; (7) reaches for <br />study should be selected to ensure statistical reliability of data samples; <br />(8) the methodology of computing weighted usable area should be replaced by a <br />method using a histogram of volume units from which mean, median, percent of <br />volume units with better than 50 percent desirability, etc. could be computed; <br />(9) a general methodology should be developed by carefully assessing the <br />variability of data over a range of stream types and geographic regions; (10) <br />information derived from actual field conditions should replace habitat <br />criteria now based on LD50 laboratory tests; (11) a regression approach should <br />be used to describe behavioral response of a species to cover; (12) the <br /> <br />~ <br /> <br />r <br /> <br />~ <br /> <br />~ <br /> <br />20 <br />