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Chapter 1 Executive Summary and Policy Directions ~ 3 alterations and increased predation pressure caused by hydropower dams are significant issues, but fall beyond the central scope of this report. This study was initiated because of significant controversy about technical issues related to fish passage and the relicensing of a large number of hydropower facilities, beginning in 1993 and cgntinuing through 2010. Major points of contro- versy are discussed below. CONTROVERSIES The need for fish passage facilities is widely accepted for anadromous fish (i.e., fish that migrate from the ocean to spawn in freshwater) (see box 1-2). Considerable controversy exists between resource agencies and hydropower operators about the passage and protection requirements for riverine fish (i.e., the so-called resident species that spend their entire lives in freshwater) (see chapter 2). ^ The need for entrainment protection and passage for riverine fish is very controversial. There is a grow- ing body of evidence that some riverine fish make significant movements that could be impeded by some hydropower facilities. The need for passage for riverine fish is most likely species- and site-spe- cific and should be tied to habitat needs for target fish populations. This will be difficult to determine without establishing goals for target species. ^ The acceptability of turbine passage for anadromous fish is site-specific and controversial. There is major concern when anadromous fish must pass through multiple dams, creating the potential for sig- nificantcumulative impacts. Passage of adult repeat spawners is also a major concern for most Atlan- tic Coast species. ^ The effects of turbine passage on fish depend on the size of the fish; their sensitivity to mechanical contact with equipment and pressure changes; and whether fish happen to be in an area near cavita- tion or where shearing forces are strong. Smaller fish are more likely to survive turbine passage than larger fish. Survival is generally higher where the turbines are operating with higher efficiency. ^ Riverine fish are entrained to some extent at virtually every site tested. Entrainment rates are variable among sites and at a single site. Entrainment rates for different species and sizes of fish change daily and seasonally. Entrainment rates of different turbines at a site can be significant. ^ Turbine mortality studies must be interpreted with caution. Studies show a wide range of results, prob- ably related to diversity of turbine designs and operating conditions, river conditions, and fish species and sizes. Turbine mortality study design is likely to affect results. Different methods may yield differ- ent results. ^ Methods for turbine mortality study include: mark-recapture studies with netting or balloon tags, and observations of net-caught naturally entrained fish, and telemetry. Methods for entrainment studies include: netting, hydroacoustic technology (used especially in the West), and telemetry tagging. These methods have advantages and disadvantages depending on target species and site conditions. Hydroacoustic technology and telemetry tagging can provide fish behavior information (e.g., tracking swimming location) useful for designing passage systems and evaluating performance. ^ Early agreement on study design would help minimize controversies between resource agencies and hydropower operators. Lack of reporting of all relevant information makes it difficult to interpret results. Standardized guidelines to determine the need, conduct, and reporting of studies could help over- come this limitation. ^ Mitigation by financial compensation is very controversial. The degree of precision necessary for eval- uation studies and how fish should be valued are items of debate. SOURCE: Office of Technology Assessment, 1995.