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Last modified
7/14/2009 5:01:46 PM
Creation date
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UCREFRP
UCREFRP Catalog Number
7933
Author
Orth, D. J.
Title
Ecological Considerations In The Development And Application Of Instream Flow-Habitat
USFW Year
1987
USFW - Doc Type
Regulated Rivers
Copyright Material
YES
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<br />Oy~ <br />lq~'l <br /> <br />''\.., <br /> <br />~'i{~/(-~Si <br />~7q3J <br /> <br />~ <br /> <br /> <br />REGULATED RIVERS: RESEARCH & MANAGEMENT, VOL. 1, 171-181 <br /> <br />" <br /> <br />ECOLOGICAL CONSIDERATIONS IN THE DEVEU <br />APPLICATION OF INSTREA~I FLOW-HABITA <br /> <br />DONALD J. ORTH <br />Department of Fisheries and Wildlife Sciences, Virginia Polytechnic Institute and State University, Balcks <br />24061, U.S.A. <br /> <br />ABSTRACf <br /> <br />Methodologies for recommending instream flows for protecting lotic ecosystems are evolving amid constructive <br />criticism. During this period of change it is important that all concerned parties are aware of the ecological factors <br />that control stream ecosystems and fish populations. Ecological factors relating to stream ecology, population <br />dynamics, energetics, predation, and competition are reviewed to explain why indices of microhabitat availability are <br />not expected to be consistent predictors of fish population density. Implications of these concepts for development <br />and application of instream flow-habitat models for recommending instream flow regimes are discussed. Current <br />ecological theory and empirical studies support the hypothesis that microhabitat availability may limit fish <br />populations but not continuously. Therefore, assessments must consider the limiting habitat events as well as <br />temperature and water quality constraints. Also, invertebrates and non-game fishes must be considered in instream <br />flow assessments because of their importance in stream ecosystems. <br /> <br />INTRODUCTION <br /> <br />Effects of flow modifications on stream habitat and biota have becOme the focus of an emerging science in <br />the last decade as evidenced by exponential growth in numbers of publications (Petts, 1984). <br />Conservation and regulatory agencies routinely deal, with the questions of what effects various stream <br />flow alterations will have on aquatic life and fisheries. Recent efforts to encourage small hydropower <br />development in the United States have intensified the interest; the Federal Energy Regulatory <br />Commission (FERC) received over 6,000 applicati6nssince 1979 compared with less than 3,000 in the <br />preceding 60 years (Tanner and Hickman, 1985). The regulatory process for hydropower development <br />and regional water resources planning is thwarted by lack of agreement on methods for recommending <br />appropriate in stream flows to meet management obje_ctives. <br />The lack of agreement on methods and interpretation is understandable because the present state of <br />the art developed largely within the last 10 years (see reviews by Stalnaker and Arnette, 1976; Stalnaker, <br />1979; Loar and Sale, 1981; Trihey and Stalnaker, 1985). The current state of the art is incorporated in <br />the Instream Flow Incremental Methodology (IFIM), outlined by Bovee (1982). The IFIM process <br />includes evaluation of effects of incremental changes in stream flow on channel structure, water quality, <br />temperature, and availability of suitable microhabitat in order to recOmmend a flow regime that will <br />maintain existing habitat conditions. The pliysical habitat component (PHABSIM; Milhous et al., 1984) <br />of the IFIM process is the most frequently used component, often to the exclusion of other components. <br />Criticisms of PHABSIM and the interpretation and application of the weighted usable area (WUA) index <br />focus on the lack of evidence that fish populations respond to changes in WUA (Mathur et al., 1985; <br />Shirvell, 1986; Scott and Shirvell, in press). Consequently, frustration among biologists exists because fish <br />population responses to flow alterations cannot be predicted. This frustation will continue until intensive, <br />long-term research efforts can advance the state of the art with methods to reliably assessinstream flow <br />needs based on biological responses (Loar and Sale, 1981). New and more complex models will be <br />needed to address biological responses to altered stream flow regimes. <br /> <br />0886-9375/87/020171-11$05.50 <br />@ 1987 by John Wiley & Sons, Ltd. <br /> <br />Received 14 July 1986 <br />Revised 30 October 1986 <br />
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