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Home My WebLink AboutSUS10026• • • HABITAT REQUIREMENTS 2 NATURAL EVENTS TIMBER 3 HARVEST 4 FOREST ROADS r 6 SILVICULTURAL TREATMENTS 7 LIVESTOCK GRAZING 8 MINING FOREST 9 CHEMICALS 10 RECREATION CAMPS 11 AND MILLS HABITAT ENHANCEMENT 12 PART I 13 PART 2 5,· • • • HABITAT REQUIREMENTS General Technical Report PN W-96 October 1979 EDITOR'S uence of Forest and Rangeland Management an Anadromous Fish Habitat in Western North America HABITAT REQUIREMENTS OF ANADROMOUS SALMONIDS D.W. REISER and T.C. BJORNN U.S. Department of Agriculture Forest Service Pacific Northwest Forest and Range Experiment Station ABSTRACT Habitat requirements of anadromous and some resident salmonid fishes have been described for various life stages, including upstream migration of adults, spawning, incubation, and juvenile rearing. Factors important in the migration of adults are water temper- ature, minimum water depth, maximum water velocity, turbidity, dis- solved oxygen, and barriers. Habitat requirements for successful spawning are suitable water temperature, water depth, water velocity, and substrate composition. Cover--riparian vegetation, undercut banks, and so on--is needed to protect salmonids waiting to spawn and may influence the selection of spawning locations. Incubation requirements incorporate both extra- and intragravel factors. Extragravel factors are: dissolved oxygen, temperature, velocity, discharge, and biochemical oxygen demand of the stream. Intragravel factors are dissolved oxygen, temperature, permeability, apparent velocity, and sediment composition. Important habitat components for juvenile rearing are fish food production areas, water quality, cover, and space. Good fish food production areas are mostly riffles with water depths of 0.15-0.91 m, water velocities of 0.30-0.46 m/s, and substrates of coarse gravel and rubble (3.2-30.4 cm). Good water quality for rearing salmonids includes mean summer water temperatures of 10.0'-14.0°C, dissolved oxygen at more than 80-percent saturation, suspended sediment less than 25 mg/liter, and fine sediment content of riffles less than 20 percent. Adequate cover--in the form of riparian vegetation, undercut banks, aquatic vegetation, and rubble-boulder areas--is needed to protect juvenile fish from predation and adverse physical factors. KEYWORDS: fish habitat, anadromous fish, salmonids, habitat needs. Gen. Tech. Rep. PNW-96, "Influence of forest and rangeland management on anadromous fish habitat in Western North America--1. Habitat requirements of anadromous salmonids. In Western North America many human activities, both commercial and recreational, take place on forest and range lands. These activities in- clude timber harvest, livestock grazing, mining, hunting, fishing, camping, backpacking, and those associated with resource uses, such as road con- struction, urbanization, water development, and treatments to improve forest growth. The many streams, rivers, lakes, and estuaries encompassed by these forest and range lands are habitat for the valuable stocks of anadromous (sea-going) and resident salmon and trout. The effects of human activities on the habitat of these salmonids has been of increasing concern to resource users and managers. Much has been learned about the responses of fish to changes in their habitat, but some of it is not widely known and the information is contained in a wide variety of sources. Scientific journals and other publications that discuss the results of fisheries research are numerous, and significant work is often published in a form that is not readily available to resource managers and to other scientists studying similar situations. In 1976, the Forest Service of the U.S. Department of Agriculture D initiated a cooperative program to define the potential problems associated with land uses in watersheds supporting anadromous fish populations, and to apply this knowledge to managing forest and range lands. Three Forest Service experiment stations--Pacific Northwest, Pacific Southwest, and Intermountain, and five regions in the National Forest System--Region 1 (Northern), Region 4 (Intermountain), Region 5 (California), Region 6 (Pacific Northwest), and Region 10 (Alaska)--as well as many Federal, State, university, and private cooperators, are participating in the program. The purpose of this series of reports is to assemble current knowledge on how management practices on forest and range lands influence anadromous fish habitat into one set of documents for resource managers, scientists, administrators, and interested citizens. Three general areas covered will be the habitat requirements of salmon and trout, the effects of various land uses on this habitat, and methods for restoration and enhancement of habitat. Fourteen papers are presently planned for this series. They will be published irregularly, but most will be available within the next 2 years. Additional topics may be addressed later, as the need for information arises. I would like to express my thanks not only to the authors of these reports, but. to the many technical reviewers, editors, illustrators, typists, and others whose efforts have made and will continue to make this compendium series a success. WILLIAM R. MEEHAN Technical Editor USDA FOREST SERVICE General Technical Report PNW-96 INFLUENCE OF FOREST AND RANGELAND MANAGEMENT ON ANADROMOUS FISH HABITAT IN THE WESTERN UNITED STATES AND CANADA William R. Meehan, Technical Editor 1. Habitat Requirements of Anadromous Salmonids Dm W. REISER AND T. C. BJORNN ldaho Cooperative Fishery Research Unit University of Idaho, Moscow PACIFIC NORTHWEST FOREST AND RANGE EXPERIMENT STATION Forest Service, U.S. Department of Agriculture Portland, Oregon PREFACE This, the first in a series of publications summarizing knowledge about the influences of forest and rangeland management on anadromous fish habitat in the Western United States, describes habitat require- ments of anadromous salmonids--the valuable salmon and trout species that use both freshwater and marine environments. ~equironents of these unique fish must be understood before we can explore the effects that natural events and human activities can have on their habitat, and on their ability to maintain productive populations with our increasing use of other forest and rangeland resources. Reports on the effects of natural watershed disturbances and various land use activities will follow. We intend to present information in these publications that will provide managers and users of the forests and rangelands of the Western United States with the most complete infomation available for estimating consequences of various management alternatives. In this series of papers, we will summarize published and unpublished reports and data as well as observations made by resource scientists and managers made during years of experience in the West. These compilations will be valuable in planning management of forest and rangeland resources, and to scientists in planning future research. The extensive lists of references will serve as a bibliography on forest and rangeland resources and their use for this part of the United States. KBERT F. TARRANT, Director Pacific Northest Forest and Range Experiment Station 809 NE Sixth Avenue Partland, OR 97232 TABLE OF CONTENTS I~UCrI~~mm~m~m~m~m~mmm~m~~m~~~mmmmmmmmmmm 1 ................................... UPS- MIGRATION CX' ADULTS 2 ~~RATURE~.m~.m~m.m~m.~.m~mmo.m~m~mm.mm.m~~~m~~~m.~mm~mm 2 .......................................... DISSOLVED OXYGE2N 2 TURBIDITY.m.mm.m.mm.~m.~.~m.~~.~.mm~~~~~m~~mm.mmm.*~**mm*m 2 ................................................. -Em. 2 S~~~m~mmm~~~m~~m~m~~m~~mmmmmmmmmmm 4 ..................................................... CX>VER 6 ............................................... TEMPERATURE 6 ..................................... SUBSTRATE COP(IH)SITIa 6 ................................................. fiEDD AREA 8 .................................. WATER DEPTH AND VELOCITY 8 ................................................ S- 9 SURF= STREAM=IMWG?AVEf, RELATION ....................... 15 DISSOLVED O~~Nm.mmmm.~.mmmmm~~~~~mm~ ..m*rn*.m.. m.mmm*mm~m 16 ~~RA~m~m~mmm~mm~~mmmm~mmm~~mm~mm~~m~~mm~mmm~mm~mmmm~ 19 BI-ICAL OXYGEN DW m~mmmmm~mm~~mm~~mm~mmmmmm~~~m~~m 20 ......................................... APP- VELOCITY 20 ............................. SUBSTRATE MA^.......... 21 S~~~mm~mm~mm~~m~~m~~~mmmmmmmmmmmmmmmmm 22 ................................ FISH FOOD PRODUCTION AREAS 24 .................................................. VELOCITY 24 ..................................................... DEPTH 24 ................................................. SUBSTRATE 25 ................................... RIP= VJEIX;EITATION.... 25 ............................................. WTER QvXIW 27 .......................................... TmpraWe 27 Dissolved Cbrygen ..................................... 28 ................... Suspended and Deposited Sediment.. 29 ...................... LITERATURE CITED.m.~.m.~.m~m.m~.mmm~m.~mo 41 Carmc>n nw Scientific nime Pink salmon Qxrm salmn Cd20 salm Sbdceye sdlmn (hkanee) Chinadc dm Cutthroat trmt Rabbw (steelhed) trout Atlantic salmon Bm trout Asctic char Brock trout m11y Vadn Ldce trmt Oncorhynchus gorbuscha (Walbaum) Oncorhynchus keta (Walbaum) Oncorhynchus kisutch (Walbaun) Oncorhynchus nerka (Walbam) Oncorhynchus tshmytscha (Walbaun) SaZmo cZarki Richardson SaZmo gairdneri Richardson Sa Zmo sa Zar Linnaeus SaZmo trutta Linnaeus Salve Zinus alpinus (Linnaeus ) SaZveZinus frmtinalis (Miail 1) SaZveZinus maZma (Walbam) SaZveZinus namaycush (Walbam) 1/ Fron .A List of ComDn and Scientific Names of Fishes £ran the - United States and Gmda," American Fisheries Society Special Publication No. 6, Third Edition, 1970, 150 p. INTRODUCTION Habitat needs of anadromous salmonids ( sea-run salmon and trout) in streams vary with the season of the year and the stage o of their life cycle. Upstream migration of adults, spawning, incubation, juvenile rearing, and seaward migration of smolts are the major life stages for most anadromous salmonids . Insofar as possible, we have defined the range of habitat conditions for each life stage that will allow a population to thrive. Throughout this paper, we have included data for sal- monids that are not anadromous because they illustrate the range of temperatures, veloc- ities, and depths of waters preferred by salmonids, and these species are generally similar to the anadromous ones. UPSTREAM --- \ MIGRATION OF ADULTS Adult salmonids returning to their natal streams must arrive at the proper time and in good health if spawning is to be successful. Unfavorable dis- charges, temperatures, tur- bidity, and water quality could delay or prevent fish from completing their migration. TEMPERATURE Selected salmonid fishes have successfully migrated upstream in water temperatures ranging from 3O to 20°C (table 1). Temperatures above the upper limits have been know stop the migration of fish.- Unusual stream temperatures can lead to disease outbreaks in migrating fish, altered timing of migration, and accelerated or retarded maturation. Most - Unpublished report, "Fisheries handbook of engineering requirements and biological criteria. Useful factors in life history of most common species," by M. C. Bell. Submitted to Fish.-Eng. Res. Prograin, Corps of Eng , , North Pac. Div., Portland, Oreg., 1973. stocks of anadromous salmonids have evolved with the temper- ature patterns of their home streams, and significant abrupt deviations from the normal pattern could adversely affect their survival. DISSOLVED OXYGEN Reduced dissolved oxygen concentrations can adversely affect the swimming performance of migrating salmonids . Maximum sustained swimming speeds of juvenile and adult coho salmon at temperatures of lo0-20°C were adversely affected when oxygen was reduced from air-saturation levels (Davis et al.1963). A sharp decrease in performance was noted at 6.5-7.0 mg/l for all temperatures tested. A similar relation has been ob- served by Graham (1949) for brook trout. Low dissolved oxygen may also elicit avoidance reactions as noted by Whitmore et al. (1960) and may cause migration to cease. The oxygen levels recommended for spawning fish (at least 80 percent of saturation, with temporary levels no lower than 5.0 mg/l) should provide the oxygen needs of migrating fish. TURBIDITY Migrating salmon will avoid or cease migration in waters with high silt loads (Cordone and Kelley 1961, Bell, see footnote 1). Bell cited a study in which salmonid fish would not move in streams where the sedi- ment content was more than 4 000 mg/l. The turbid water resulted from a landslide, Turbid water will absorb more radiation than clear water and thus may in- directly result in a thermal barrier to migration. BARRIERS Waterfalls, debris jams, and excessive velocities may also impede migrating fish. Falls that are insurmountable Table 1 -Water temperature, depth, and velocity criteria for successful upstream migration of adult salmon and trout. Species of fish Temperature 1 / range- Minimum Maxi mum depth- velocity- 2/ 1 I 1 "C - Meters Meters/second Fall chinook salmon Spring chinook salmon Summer chi nook salmon Chum salmon Coho salmon Pink salmon Sockeye salmon Steel head trout Large trout Trout 1/ From Bell (see text footnote 1). - 2/ From Thompson (1 972). - 3/ Basedonfishsize. - at one time of the year may bye passed by migrating fish at other times when flows have changed. Stuart (1962) deter- mined in laboratory studies that ideal leaping conditions for fish are obtained with a ratio of a height of falls to depth of pool of 1:1.25. Figure 1 from Eiserman et al. (1975) depicts the leaping behavior of salmonids observed by Stuart. Given suitable conditions, salmon and steelhead can get past many obstacles that appear to be barriers. Both Jones (1959) and Stuart (1962) observed salmon jumping 2-3 m. Debris jams, whether nat- ural or caused by human activ- ities, can prevent or delay upstream migration. Chapman (1962) cited a study in which a 75-percent decrease in spawning salmon in one stream was attrib- uted to debris blockage. Debris barriers often form large pools and sediment traps that, if released, could adversely affect downstream spawning areas. Some logs, leaves, dams, and so on, in streams are beneficial as cover for adult and juvenile fish. All debris jams should be evaluated care- fully before they are removed. Water velocities may exceed the swimming ability of migrating fish at channel constrictions during snow melt and storm runoff. Migration resumes when streamflows and associated velocities have decreased. The swimming abilities of fish are usually described in terms of cruising speed--the speed a fish can swim for an extended period of time (hours), usually ranging from 2 to 4 body lengths per second; sustained speed--the speed a fish can maintain for a period of several minutes, ranging from 4 to 7 body lengths per second; and darting or burst speed--the speed a fish can swim for a few seconds, ranging from 8 to 12 body lengths per second (Bell, see footnote 1; Watts 1974; table 2). According to Bell, cruising speed is used Figure 1-Leaping ability of salmonids (from Eiserman et al. 1975, diagrams drawn after Stuart 1962): A. Falling water enters the pool at nearly a 90" angle. A standing wave lies close to the waterfall where trout use its upward thrust in leaping. Plunge-pool depth is 1.25 times the distance (h) from the crest of the waterfall to the water level of the pool. B. The height of fall is the same, but pool depth is less. The standing wave is formed too far from the ledge to be useful to leaping trout. C. Flow down a gradual incline is slow enough to allow passage of ascending trout. D. Flow over a steeper incline is more than trout can swim against for much distance. Trout may even be repulsed in the standing wave at the foot of the incline. They sometimes leap futilely from the standing wave. E. A shorter barrier with outflow over steep incline may be ascended by trout with difficulty. FLOW (CUBIC FEET PER SECOND) Figure 2-Salmonid passage flow determination (from Thompson 1972). during migration, sustained speed for passage through dif- ficult areas, and darting speed for escape and feeding. Velo- cities of 3-4 m/s approach the upper swimming ability of salmon and steelhead and may retard up- stream migration. STREAMFLOW Migration can also be hampered by too little streamflow and resulting shallow water. Thompson (1972) established passage criteria for various salmonids based on minimum depth and maximum velocities (table 1). Stream discharges that will provide suitable depths and velocities for adult passage ( figure 2) can be determined from the criteria and techniques described by Thompson (1972): 1/ Table 2-Swimming abilities of average size adult salmonids- Species of fish I 1 I _--_______________ Meters per second--------------- I Cruising speed Chinook Coho Sockeye Steel head Trout Brown trout 1/ From Bell (see text footnote 1). - Sustained speed ... shallow bars most crit- ical to passage of adult fish are located and a linear transect marked which £01 lows the shal- lowest course from bank to bank. At each of several flows, the total width and longest continuous portion of the transect meeting minimum depth and maximum velocity criteria are measured. For each tran- sect, the flow is selected that meets the criteria on at least 25 percent of the total transect width and a Darting speed continuous portion equal- ling at least 10 percent of its total width. The mean selected flow from all transects is recommended as the minimum flow for passage. Thompson (1972) noted that maximum acceptable passage flows could theoretically be defined, but we have not attempted to do so in this paper. Baxter (1961) reports that salmon need 30-50 percent of the average annual flow for passage through the lower and middle reaches in Scottish rivers and up to 70 percent for headwater streams. Cover, substrate composi- tion, and water quality and quantity are important habitat elements for anadromous sal- monids before and during spawning. COVER Cover for fish can be provided by overhanging vege- tation, undercut banks, sub- merged vegetation, submerged objects--e.g. logs and rocks, floating debris, and water depth and turbulence (Giger 1973). Cover can protect the fish from disturbance and predation and also provide shade. Some anad- romous fish--chinook salmon and steelhead, for example--enter freshwater streams months before they spawn, and cover is essen- tial for fish waiting to spawn. Many spawning areas are rela- tively open segments on streams where fish are vulnerable to disturbance and predation during redd (nest) construction and spawning. Nearness of cover to spawning areas may be a factor in the actual selection of spawning sites by some species. Johnson et al. (1966) and Reiser and Wesche (1977) noted that many spawning brown trout selected areas adjacent to undercut banks and overhanging vegetation. Reiser and Wesche (1977) speculated that the early spawners and large dominant fish may select areas by cover. As these areas become occupied, the late spawners and small fish are forced to use relatively un- protected sites. Given a choice between two spawning areas, one with cover and one without, the fish would select the area with cover. TEMPERATURE Successful spawning of salmonids has occurred in water temperatures ranging from 2.2 to 20. O°C (table 3 ) . A sudden drop in temperature may cause all spawning activity to cease, resulting in lowered nest build- ing activity and reduced pro- duction (see footnote 1). SUBSTRATE COMPOSITION The suitability of a parti- cular size gravel substrate depends mostly on fish size. Large fish can build redds in large substrate. To determine the substrate composition preferred by various salmonids, many investigators (Burner 1951, Cope 1957, Warner 1963, Orcutt et al. 1968, Hunter 1973, Reiser and Wesche 1977) collected gravel samples from active redds and graded them through a series of sieves. The substrate compo- sition selected in artificial spawning channels reflects the judgment of those who determined the particle sizes best suited for selected species. In the Robertson Creek spawning channels, gravel ranging from 2 to 10 cm was used for pink, coho, and spring chinook salmon (Lucas 1959). In the Jones Creek spawning channel, gravel ranged from 0.6 to 3.8 cm (MacKinnon et al. 1961). The Tehama-Colusa 1/ Table 3-Recommended temperatures for spawning and incubation of salmonid fishes- Fall chinook Spring chinook Summer chinook Chum Coho Pink Sockeye KO kanee Steel head Rainbow Cutthroat Brown Species 11 From Be1 1 (see text footnote 1). - J' 21 The higher and lower values are threshold temperatures at which - mortality will increase if exceeded. Eggs will survive and devel op normal ly at 1 ower temperatures than indicated, provided initial development of the embryo has progressed to a stage that is tolerant of colder water. 31 From Hunter (1973). vfl - Table 4-Water depth, velocity, and substrate size criteria for anadromous and other salmonid spawning areas Spawni ng temperature Incubation temperature- 2/ Fall chinook Spring chinook Summer chinook Chum Coho Pink salmon soc key&/ Kokanee Steel head Rainbow trout Cutthroat Brown trout Species of fish Thompson (1 972) Thompson (1 972) ~ei serg/ Smith (1973) Thompson 11 972) Collin s4 smi th-(1973) Smith (1973) Smith (1973) Hunter (1 973) Thompson (1 972) 1/ From Be1 1 (see text footnote 1). J - 2/ Unpublished data of D. W. Reiser, Idaho Coop. Fish Res. Unit, J - Moscow. 1978. 31 Estimated from other criteria. -47 - See text footnote 3. 51 No specific criteria established. - 61 From Hunter (1973). 1/ - Meters Cm/s Centimeters Source Depth Velocity Substrate size spawning channels contain gravel that ranges from 1.9 to 15.2 cm (Pollock 1969). Bell (see footnote 1) states that, in general, the spawning bed in artificial channels should be composed of 80 percent 1.3-to 3 -8-cm gravel with the balance up to 10.2 cm. Acceptable ranges of substrate size for various salmonids are summarized in table 4. REDD AREA Area of gravel substrate required for a spawning pair varies with the species (table 5). Burner (1951) proposed that a conservative estimate of the number of salmon a stream could accommodate could be obtained by dividing the area suitable for spawning by four times the average redd area. Redd area can be computed by measuring the total length of the redd (upper edge of pit to lower edge of tailspill) and the average of several equidistant widths. WATER DEPTH AND VELOCITY Preferred water depths and velocities for various spawning salmonids have been determined by measuring water depth and velocity ove5,active redds (Sams and Pearson,- Thompson 1972, Smith 1973, Hooper 1973, Hunter 1973, Reiser and Wesche 1977). These measurements were usually taken at the upstream edge of the redd because that point most closely approximates conditions before redd construction and reflects the depths and velo- cities selected by the fish. Preferred depth and velocity criteria have been variously - 2/ Unpublished report, "A study to develop methods for determining spawning flows for anadromous sal- monids," by R. E. Sams and L. S. Pearson. Oreg . Fish Comm., Portland, 1963. defined: Thompson (1972) used a 90-to 95-percent confidence limit; Hunter (1973) used the middle 80-90 percent of the measurements; Smith (1973) used a two-sided tolerance limit within which there was 95- percent confidence that 80 percent of the measurements would occur with a normal dis- tribution; others have simply listed ranges of depth and velocity. Water depth and velocity criteria for salmonids as defined by different investi- gators are found in tables 4 and Riffle Riffle - Riffle Figure 3-Longitudinal sections of spawning areas (from Reiser and Wesche 1977): A. Convexity of the substrate at pool-riffle interchange induces downwelling of water into the gravel. Area likely to be used for spawning is marked with an X. B. Redd construction results in negligible currents in the pit (facilitating egg deposition) and increased currents over and through (downwelling) the tailspill. C. Egg-covering activity results in the formation of a second pit which may also be used for spawning, as well as covering the eggs in the first pit. Increased permeability and the convexity of the tailspill substrate induces downwelling of water into the gravel, creating a current past eggs, bringing oxygen to them and removing metabolic wastes. Table 5-Average area of salmonid redds and area recommended per spawning pair in channels2 Species Source ------ Sauare meters----- Average area of redd Spring chinook Fall chinook Summer chinook Coho Chum Sockeye Pink Area recommended per spawning pair Pink Steel head Steel head Rainbow Cutthroat Brown Burner (1 951 ) 3.3 Burner (1 951 ) 5.1 Burner (1951 ) 5.1 Burner (1951 ) 2.8 Burner (1951) 2.3 Burner (1 951 ) 1.8 Hourston and .6 MacKinnon (1957) Wells and .6-.9 McNei 1 (1 970) Orcutt et al. (1968) 5.4 Hunter (1 973) 4.4 Hunter (1 973) .2 Hunter (1973) .09-. 9 Rei ser and .5 Wesche (1 977) 1/ Modified from Clay (1961). - / Many salmonids prefer to spawn at the pool-riffle inter- change (Hazzard 1932, Hobbs 1937, Smith 1941, Stuart 1953, Briggs 1953). Tautz and Groot (1975) reported that chum salmon chose to spawn in an acceler- ating flow, such as that found at a pool-riffle interchange. By placing crystals of potassium permanganate on the gravel surface, Stuart (1953) demon- strated the presence of a down- welling current at these inter- change areas and suggested that the current may assist the fish in maintajning its position with a minimum of effort. The gravel in these areas was easy to excavate and relatively free of silt and debris. The nature of currents before, during, and after spawning is shown in figure 3. STREAMFLOW Streamflow regulates the amount of spawning area avail- able. D. H. Fry in Hooper (1973) summarizes the effect of discharge on the amount of spawning area in a stream. As flows increase, more and more gravel is covered and becomes suitable for spawning. As flows con- tinue to increase, velocities in some places become too high for spawning, thus canceling out the benefit of increases in usable spawning area near the edges of the stream. Eventually, as flows in- crease, the losses begin to outweigh the gains, and the actual spawning capacity of the stream starts to decrease. wide variation of hydraulic characteristics Table 6-Water depth, velocity, and size of substrate measured in spawning areas of salmonids Smith (1973) 2.24 30-76 Spring chinook Chambers et a1.I' .46-. 53 53-69 Sams and pearso&' L. 18 .08- .85 Thompson (1972)~ 2.24 30-91 Remarks Species Smith (1973) ~eised' >.I5 14-69 Sumner chinook Reiser 1' 8' .30- .85 25-109 Chum salmon Thompson (1 972) 2.18 46-97 Meters Cm/s Centimeters -- Chinook salmon Hamilton and >O. 24 31 - - Oregon-Coquille River Remington (1962) Fall chinook warned/ .12-1.22 15-107 California-American, and Consumnes westgat&/ Rivers Kier (1964) 2.24 31-92 California-Feather, Eel, and Mad Rantz (1964) River Systems Horton and ~ogers~ 2.21 37-107 California-Van Ouzen River Chambers et a1 .q - .30-.46 30-69 Washington-Columbia River and Vat 0.4 ft above bed tributaries Sams and ~ears.06' 2-18 .27-94 Oregon - 4 streams in Willamette 107 redds sampled; V at River Basin 0.63 depth or 0.2 ft and 0.8 depth from surface Thompson (1 97216' 2.24 30-91 90-958 confidence interval ; Oregon, 440 redds sampled; wide range of streams streams represented a Coho salmon Source Smith (1973)~' 2.18 46-101 ~ol 1 ings 91 .15-.53 21-101 Chambers et a1 .g .30-. 38 37-55 Depth Sams and Pearson (1963)5/,. 15 14-93 Tolerance interval; Oregon, 7 streams 50 redds sampled; V at with varying hydraulic conditions 0.4 ft above bed - Washington-Columbia River and V at 0.4 ft above bed Velocity tributaries Range; Oregon, 3 streams in 270 redds sampled; V at Willamette River Basin 0.6 ft depth or 0.2 ft and 0.8 ft depth from surface. 90-95% confidence interval ; Oregon, 158 redds sampled ; wide range of streams streams representative of a wide variation of hydraulic characteristics Tolerance interval; Oregon, 7 streams 142 redds sampled; V at Substrate with varying hydraulic conditions 0.4 ft above bed Range; Idaho, 5 small streams 58 redds sampled; V at 0.6 ft depth from surface Range; Idaho, Salmon River 50 redds sampled; V at 0.6 ft depth from surface 90-952 confidence interval ; Oregon, 177 redds sampled; on a wide range of streams streams represented a wide variation of How and where developed hydraulic characteristics Tolerance interval ; Oregon, 5 214 redds sampled; V at streams with varying hydraulic 0.4 ft above bed. conditions -- Vmeasured 0.4 ft above bed Washington, Columbia River and Redds measured 0.4 ft above tributaries Range; Oregon, 4 streams bed 123 redds sampled; V at 0.6 ft depth or 0.2 ft and 0.8 ft depth from surface Table 6-Water depth, velocity, and size of substrate measured in spawning areas of salmonids -(Continued) Meters Cm/s Centimeters Coho salmon Thompson (19~2)~' 20.18 30-91 -- Species 90-958 confidence interval; Oregon, 10-12 streams with varying hydraulic conditions 251 redds sampled; streams represent wide variation of hydraulic characteristics 128 redds sampled; V measured 0.4 ft above bed Source Smith (1973) Tolerance interval; Oregon, 7 streams with varying hydraulic conditions Depth Pink salmon ~ol 1 ings 61 91 Sockeye salmon Chambers et a1.4' Clay (1961 ) Kokanee Thompson (1972) - V measured 0.4 ft above bed - V at 0.4 ft above bed - V at 0.4 ft above bed 106 redds sampled; streams represent wide variation of hydraulic characteristics 106 redds sampled; Vat 0.4 ft above bed Washington Remarks Velocity 90-95% confidence interval; Oregon, wide range of streams Smith (1973161 Substrate Tolerance interval; Oregon, 3 streams with varying hydraulic How and where developed conditions Middle 80% of range; Washington, flow 2-30 ft3/s 95% confidence interval ; Oregon 177 redds sampled; V at 0.4 ft or 0.25-0.30 above bed 51 redds sampled 115 redds sampled; V at 0.4 ft above bed Steelhead trout Winter steel head Smith (1973)c' Tolerance interval; Oregon, 11 streams with varying hydraulic conditions Range; Washington Middle 90% of range; Washington, 19 streams with varying hydraulic ~ngma@/ Hunter (1973) 62 redds sampled 114 redds sampled; Vat 0.4 ft or 0.25-0.30 ft above bed 19 redds sampled; V at 0.4 ft or 0.25-0.30 ft above bed 30 redds sampled; V at 0.4 ft or 0.25-0.30 ft above bed 4 redrls sampled; V at 0.4 ft or 0.25-0.30 ft above conditions _ Range; Washington Hunter (1973) Range; Washington, on streams of 180 ft3/s Range; Washington, Satsop River bed 90 redds sampled; V 83 redds sampled D; V at 0.4 ft above bed 54 redds sampled; V measured at the surface Sumner steel head Smith (1973) 2.24 43-97 - - Tolerance interval ; Oregon, Deschutes River Orcutt et al. (1968) .21-21.52 24-55 1.27-10.16 Range; Idaho, 6 streams in Clearwater and Salmon River watersheds Table 6-Water depth, velocity, and size of substrate measured in spawning areas of salmonids -(Continued) Meters Cm/s Centimeters - -- Sumner steelhead ~eise& 0.12-.41 38-100 -- Range; Idaho, 3 streams 46 redds sampled; V measured at 0.6 ft depth from surface Rainbow trout Smith (1973)g > .18 48-91 0.64-5.18 Tolerance interval ; Oregon, 51 redds sampled; V at Deschutes River 0.4 ft above bed Hooper (1973) .21-.33 43-82 .64-7.62 Range; California, Feather River 10 redds sampled; V at 0.21 above bed Remarks . .- (resident) (sea-run) Brown trout Bovee (1974) Waters (1976) Hartman (1969) Cutthroat trout Hooper (1973) Cedarholm (in Hunter 1973) Hunter (1973) Species Brown trout Depth Source Hunter (1973) Smith (1973) (Hunter 1973) Velocity - - Estimated from 1 iterature - - California, Pit River - - British Columbia, Kootenay Lake .16-.64 Range; California - - Range; Washington 3 redds sampled .64-5.08 Range; Washington, streams 23 redds sampled; V at 0.5-2.0 ft3/s 0.4 ft or 0.25-0.30 ft from bed .64-10.16 Range; Washington, streams 16 redds sampled; V at 5.0-15.0 ft3/s 0.4 ft or 0.25-0.30 ft from bed .64-7.62 Tolerance interval; Oregon, 5 11 5 redds sampled; V at streams with varying hydraulic 0.4 ft from bed Substrate conditions Thompson (1972)g 2.24 21-64 - - 90-95% confidence interval ; Oregon, 11 5 redds sampled How and where developed on a wide range of streams Hooper (1973) -- 30-91 .64-7.62 Range; California Bovee (1974) 2.15 40-52 - - Estimated from literature Reiser and Wesche (1977) 2.09 14-46 .64-7.62 Middle 80% of range; Wyoming, 121 redds sampled; V at 5 small streams 0.6 ft depth from surface L1unpublished report, "The relationship between flow and available salmon spawning gravel on the American River below Nimbus Dam," by K. Warner. Calif. Dep. Fish and Game Admin., Sacramento, 1953. l/~npubl ished report. "The relationship between flow and usable salmon spawning gravel, Consumnes River, 1956," by J. Westgate. Calif. Dep. Fish and Game, Inland Fish. Admin. Rep. 58-2, Sacramento, 1958. /unpublished report, "The optimum stream flow requirements for king salmon spawning in the Van Duzen River, Humboldt County, California," by J. L. Horton and D. W. Rogers. Calif. Dep. Fish and Game, Water Proj. Branch Admin. Rep. 69-2, Sacramento, 1969. 'unpublished report, "Research relating to study of spawning grounds in natural areas," by J. S. Chambers, G. H. Allen, and R. T. Pressey. Wash. Dep. Fish., Olympia, 1955. 5/~ee text footnote 2. g~ecormnended spawning criteria. L1unpublished data of D. W. Reiser, Idaho Coop. Fish. Res. Unit, Moscow, 1977 /see footnote 2, table 4. y~ee text footnote 3. X1unpublished progress report, steelhead redd study, by R. G. Engman. Wash. State Dep. Game, Olympia, 1970. u~ersonal comnunication, J. W. Hunter, Wash. Dep. Game, Olympia, 1976. If spawning area is plotted against streamflow, the curve will usually show a rise to a relatively wide plateau followed by a gradual decline. Using the criteria described, methods have been developed for recommending stream discharges for spawning. Figures 4 and 5, taken from Collings (1972), exemplify the process of depth and velocity contouring to determine the area suitable for spawning at a given discharge. Another method (Thompson 1972) uses cross channel transects on spawning bars and consists of quantifying the width af the stream at different flows that meet depth and velocity criteria ( fig. 6 ) . When measurements have been taken over a wide range of flows, a graph is plotted of flow versus suitable spawning areas (Collings 1972, and fig. 7) or usable width (Thompson 1972, and fig. 8 ) . The optimum spawning flow is defined as the discharge at which the largest spawning area or usable width occurs. Detailed descrip- tions of spawning flow method- ologies are described by Sams and Pearson (see footnote 2), on (1972), Collings (1972, TRf'), Waters (19761, and Stalnaker and Arnette (1976). - 3' Unpublished report. "~ener- alization of spawning and rearing discharges for several Pacific salmon species in western Washington," by M. R. Collings. U.S. Geol. Surv., open file report. 1974. Section 2 Section 4 ~dg!? of water / Edge of dank full Section 2 water -surface area 0 / \ Section 4 / VELOCITY CONTOURS IN FEET PER SECOND /WS of flow / 0 .' c- _--- _ ------ _-___ __----- Figure 4-Example of water depth and velocity contouring for one river discharge in a study reach of the North Nemah River (from Collings 1972). Section 2 Section 4 / b '~d~e of bank full water-surface area DISCHARGE: 94.6 ft2 AREA OF PREFERRED DEPTH: 1045 ft2, BETWEEN 1.0 and 1.5 ft AREA OF PREFERRED VELOCITY: 1706 ft2, BETWEEN 1.0 and 2.25ftls AREA PREFERRED FOR SPAWNING: 726 ft2 Figure 5-Determining area of study reach that is preferred for spawning by fall chinook salmon at one river discharge, North Nemah River (from Collings 1972). 1 25 FEET ~4 SPAWNING BAR CROSS SECTION Spawninq flow criteria Minimum depth = 0.6ft Velocity = less than 3.0 but greater .7 1.9 than 1.0 ftls Flow = width x mean depth x mean velocitv Flow = 25ft x 0.75ft x 1.93ft/s = 36 h3/s Stream width usable for spawning Usable width = 't'eam width usable 10 stations - -- 25ftx 6 10 = 15.0ft all Chinook loo0 4 Greatest spawnable------1- 10 0 0 10 20 50 100 200 DISCHARGE (CUBIC FEET PER SECOND) Figure 6-Transect method of determining stream width usable for spawning (from Thompson 1972). FLOW (CUBIC FEET PER SECOND) Figure 8-Method (usable width technique) for determining spawning flow (from Thompson 1972). Figure 7-Method (usable area technique) for selecting preferred spawning discharge, North Nemah River (from Collings 1972). INCUBATION Although incubation is inextricably tied to spawning, the habitat requirements of embryos during incubation are different from those of adults while spawning and warrant a separate discussion. When an adult fish selects a spawning site, the incubation environment is also being selected. Suc- cessful incubation and emergence of fry, however, is dependent on both extragravel and intragravel chemical, physical, and hydraulic parameters--dissolved oxygen (DO), water temperature, bio- chemical oxygen demand (BOD) of material carried in water and in substrate, substrate size (percentage fines) , channel gradient, channel configuration, water depth (head), surface water discharge and velocity, permeability, porosity, and apparent velocity in gravel. SURFACE STREAM. INTRAGRAVEL RELATION Interchange of water in a stream with that in streambed gravels has been demonstrated by Stuart (1953), Sheridan (1962), Vaux (1962). Vaux (1962) stated that the initial source of oxygen in intragravel water is the atmosphere and listed the following three steps for trans- port of oxygen to the intra- gravel environment: Dissolution of oxygen through air-water interface into stream water. Transport of oxygenated water to the stream bottom. Interchange of oxygenated water from the stream into the porous gravel interior. Factors that control the water interchange between stream and gravel bed are: stream surface profile, gravel permeability, gravel bed depth, and irregularity of the stream- bed surface (Vaux 1962, 1968). Sheridan (1962) noted in salmon spawning areas in southeast Alaska, that ground water con- tained very little oxygen and that the oxygen content of intragravel water decreased with gravel depth; thus the major source of oxygen in intragravel water is the stream itself, Wells and McNeil (1970) attrib- uted high intragravel oxygen in pink salmon spawning beds to high permeability of the sub- strate and stream gradient, Intragravel water temper- atures are similarly influenced by temperatures of the stream. Ringler (1970) and Ringler and Hal 1 ( 1975 ) observed that temper- atures of intragravel water lagged 2-6 h behind those of surface waters in attaining diurnal maximum--a function of the interchange rate of surface and intragravel water. Apparent velocity (velocity of water moving through gravel ) is a function of the hydraulic head and the permeability of the Surface flow 3.5 ft3/s gravel (Coble 1961). Thus, as depth of surface water increases, a corresponding increase in apparent velocity can be ex- pected. Wickett (1954) found a direct relation between gage height readings in a stream and subsurface flow ( fig. 9) . Reduction in permeability from fine sediment deposition will reduce both the interchange of surface and intragravel water and the apparent velocity of the intragravel water (Gangmark and Bakkala 1960, Wickett 1962, Cooper 1965 ) . I I I I I I .2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 GAGE READING MAIN STREAM (FEET) DISSOLVED OXYGEN Figure 9-Relation between subsurface water flow 30 cm (12 in) in a controlled-flow side channel and main stream Critical concentrations of gage readings. The subsurface flow varied with changes dissolved oxyqen have been in discharge of the main stream adjacent to the controlled-flow side channel (from Wickett 1954, courtesy of the Journal of the Fisheries Research Board of experimentali; determined for salmonid embryos at different Canada). Table 7-Critical levels of dissolved oxygen for salmonid embryos at various stages of development Wickett (1954) Chum salmon Pre-eyed Pre-eyed Pre-eyed Faintly eyed A1 derdi ce Chum salmon - - et a1 . (1958) - - critical value of dissolved oxygen Li ndroth (1 942) At1 antic Doomed salmon Nearly hatching Hatching Temperature units- 1 1 Hayes et al. Atlantic Eyed 25 - - (1 951 ) salmon Hatching 50 - - Source 11 A temperature unit equals 1 OF above freezing (32°F) for a period of 24 h. - 21 From Wickett (1954). - Stage of devel opment Species Days developmental stages (Lindroth 1942, Hayes et al. 1951, Wickett 1954, Alderdice et al. 1958). Critical oxygen levels defined by Alderdice et al. (1958) are those that barely satisfy res- piratory demands (table 7). Doudoroff and Warren (1965) believe the critical levels in table 7 are unreliable, because they found that embryos exposed to dissolved oxygen levels below saturation throughout develop- ment were smaller and that hatching was delayed or occurred prematurely. From laboratory tests with coho, chum, and chinook, and steelhead eggs by Alderdice et a1 . ( 1958 ) , Silver et al. (1963), and Shumway et al. (1964), the following sum- mary of oxygen concentration and egg development has been pre- pared: Sac fry from embryos in- cubated in low and inter- mediate oxygen concentra- tions were smaller and weaker than sac fry reared at higher concentrations, and thus they may not survive as well as larger fry (Silver et a1 . 1963, and figs. 10 and 11). Reduced oxygen concentra- tions lead to smaller newly hatched fry and a lengthened incubation period (Shumway et al. 1964, and figs. 12 and 13). a Low oxygen concentrations in the early stages of development may delay hatching, increase the incidence of anomalies, or both. Low oxygen concen- tration during the latter stages of development may stimulate premature hatch- ing (Alderdice et al. 1958). Water Velocity 14 ! 2 I 3 I I I I I I,, 4 5 6 7 8 9101112 DISSOLVED OXYGEN CONCENTRATION (MILLIGRAMS PER LITER) Figure 10-Relation between mean lengths of steelhead trout sac fry when hatched and dissolved oxygen concentrations at which the embryos were incubated at different water velocities and at 95°C (from Silver et al. 1963). Water velocity 1350 cm/h A 580cm/h 92cm/h 18 4 5 6 7 8 9101112 DISSOLVED OXYGEN CONCENTRATION (MILLIGRAMS PER LITER) Figure 11-Relation between mean lengths of chinook salmon sac fry at hatching and dissolved oxygen concentrations at which the embryos were incubated at different water velocities and at 11 "C (from Silver et al. 1963). "IPl DISSOLVED OXYGEN CONCENTRATION (MILLIGRAMS PER LITER) Figure 12-Three-dimensional diagram of effect of oxygen concentration and water velocity on the mean dry weights of newly hatched coho salmon fry. The two broken lines (curves) delimit the reduced oxygen concentrations at different water velocities, and also the reduced velocities at different oxygen concentrations that resulted in reductions of the dry weights of fry to less than 80 percent (upper broken line) and less than 67 percent (lower broken line) of the mean weight of fry that hatched at the highest oxygen concentration and water velocity tested (from Shumway et al. 1964). ' *o&&, DISSOLVED OXYGEN CONCENTRATION (MILLIGRAMS PER LITER) Figure 13-Three-dimensional diagram of "hatching delay" (median hatching time, in days, minus 44) of coho salmon fry in relation to both oxygen concentration and water velocity (from Shumway et al. 1964). In field studies, Coble (1961) found a positive correl- ation between steelhead embryo survival and intragravel dis- solved oxygen content ( fig . 14 ) . A similar relation was reported by Phillips and Campbell (1961) for coho salmon and steelhead (fig. 15). Based on their field experiments, Phil lips and Campbell concluded that intra- gravel oxygen concentration must average 8 mg/l for high survival of coho salmon and steelhead embryos. Brannon (1965) com- pared newly hatched sockeye salmon fry developed at three different oxygen levels, and found length and other ana- tomical differences in the three groups (table 8); however, those raised in low oxygen concen- trations eventually attained nearly the same weight by the fry stage as did those incubated J O2345678910 DISSOLVED OXYGEN CONCENTRATION (MILLIGRAMS PER LITER) Figure 14-Relation between dissolved oxygen concentration and embryo survival (from Coble 1961). MEAN DISSOLVED OXYGEN CONCENTRATION (MILLIGRAMS PER LITER) Figure 15-Relation of mean dissolved oxygen to survival of coho embryos, Needle Branch, December 20,1960, to February 28, 1961 (from Phillips and Campbell 1961). Table 8-Characteristics of alevins at hatching after being incubated in three oxygen concentrations (from Brannon 1965) Temperature units to 50% hatching 1200 1200 1200 Description Length in mi 11 imeters 16.3 18.6 19.7 Yolk sac shape Spherical Longitudinal Longitudinal Pigmentation Lightly on On head and On head and head starting on back back O2 concen tra t i on (mg/ 1 ) Visibility of the Not visible Distinguish- Readily visible dorsal and anal fin rays able 3.0 Caudal fin devel opment Forming Forming We1 1 advanced in water fully saturated with oxygen. Although dissolved oxygen concentrations required for successful incubation depend on both species and develop- mental stage, concentrations at or near saturation with tem- porary reductions no lower than 5.0 mg/l are recommended for anadromous salmonids. 6,O TEMPERATURE 11.9 There are upper and lower temperature limits (thresholds) for successful incubation of salmonid eggs (table 3). Combs and Burrows (1957) and Combs (1965) noted that pink and chinook salmon eggs could toler- ate long periods of low temper- ature, provided the initial temperature was above 6.0°C and embryogenesis had proceeded to a particular developmental stage. Combs and Burrows (1957) be- lieved salmon eggs deposited in water colder than 4.5OC would not produce as viable a fish as eggs spawned into warmer water. In many streams containing incubating salmonid eggs, water temperatures are colder than 4.5OC during the winter; eggs develop normally and success- fully, however, because spawning and initial embryo development occur when temperatures are warmer. Zxtremely cold water and air temperature can cause mortality among incubating eggs and fry by the formation of frazil or anchor ice that reduces water interchange. Anchor ice normally forms in shallow water typical of spawning areas and may completely blanket the surface of the substrate and thereby prevent water inter- change between stream and gravel. In addition, ice dams may form that can impede flow or even dewater spawning areas, Sub- sequent melting of the dam may cause floodlike conditions resulting in the displacement and scouring of redds, In an egg planting experiment, Reiser and Wesche (1977) found eggs in Vibert boxes completely frozen even though buried 15 cm in the substrate and covered with more than 13 cm of water. Anchor ice had formed at least twice during the incubation period. Neave (1953) and McNeil (1966) also noted the problems of freezing on egg survival. BIOCHEMICAL OXYGEN DEMAND The oxygen demand of organic matter in the stream may reduce the oxygen concentration, partic- ularly in the intragravel envi- ronment. The impact of organic matter in a stream depends on the chemical, physical, and hydraulic characteristics (for example, dissolved oxygen con- tent, temperature, and reaer- ation capability) of the stream. Excessive recruitment of organic material to a stream may result in reduced oxygen concentrations and detrimental impacts on eggs. APPARENT VELOCITY The single most important hydraulic component in the intragravel environment used for egg incubation is apparent velocity, defined as the rate of seepage and expressed as the volume of liquid flowing per unit time through a unit area normal to the direction of flow (Terhune 1958, Coble 1961, Vaux 1968). Apparent velocity is important in bringing dissolved oxygen to the eggs and removing metabolic waste products. High oxygen levels do not, in themselves, guarantee high egg survival. In two redds with similar dissolved oxygen con- centrations but different apparent velocities, embryonic develop- ment may be better in the redd with the higher rate of water exchange (Coble 1961). Coble states that, in general, when apparent velocities are low, oxygen concentrations will he low and, when they are high, oxygen levels are usually high. Others have found egg survival related to apparent velocity-- for example, Pyper (in Cooper 1965) in sockeye eggs (fig. 16), Coble (1961) in steelhead (fig. 17), Gangmark and Bakkala (1960) in chinook, Wickett (1962) in pink salmon, and Phillips and Campbell (1961) in coho and steelhead. In the last study, high egg survivals were asso- ciated with apparent velocities of more than 20 cm/h. Wickett (1962) found low survival in areas where apparent velocities were 0.5-1.5 cm/h and high survivals where velocities were more than 7 cm/h. Silver et al. (1963) and Shumway et al. (1964) related apparent velocity to size of fry at a hatchery. Silver et al. found that size of steelhead and chinook fry de- pended on apparent velocities, even at velocities as high as 740-1350 cm/h. Shumway et al. found that reduced velocities (3-10 cm/h) resulted in de- creased size of fry at all oxygen levels tested (2.5-11.5 mg/l) APPARENT VELOCITY (CENTIMETERS PER SECOND) Figure 16-Relation between rate of flow of water through a gravel bed and the survival of eyed sockeye eggs in the gravel (from Cooper 1965). 0 1 2 5 10 20 50 100 MEAN APPARENT VELOCITY (CENIIMETERS PER HOUR) Figure 17-Relation between apparent velocity and embryo survival (from Coble 1961). SUBSTRATE MATERIALS Spawning bed materials a1 so influence the development and emergence of fry. ~ermeability of the substrate (the ability of a material to transmit fluids) sets the range of subsurface water velocities (Wickett 1962). Low permeabilities result in lower apparent velocities and reduced oxygen delivery to and metabolite removal from the eggs. Wickett (1958) found that survival of pink and chum salmoc eggs was related to permeability (fig. 18). McNeil and Ahnell (1964) concluded that highly productive spawning streams had gravels with high permeability. Permeability was high (24,000 cm/h) when bottom materials had less than 5 percent (by volume) sands and silts that passed through a 0.833 mm sieve and was relatively low (less than 1 300 cm/h) when fine sediments made up more than 15 percent of the bottom material. Successful fry emergence is hindered by excessive amounts of sand and silt in the gravel. Even though embryos may hatch and develop, survival will be poor if they cannot emerge. Koski (1966) examined redds PERMEABILITY OF STREAMBED GRAVELS (CENTIMETERS PER MINUTE) Figure 18-Observed relation reported by Wickett (1958) between permeability of spawning beds and survival of pink and chum salmon to the migrant fry stage (from McNeil and Ahnell 1964). Biornn (1969) Chinook salmon - Steelhead - --- 20- 10- 0 10 20 30 40 50 60 PERCENTAGE FINE SEDIMENT Figure 19-Percentage emergence of fry from newly fertilized eggs in gravel-sand mixtures. Fine sediment was granitic sand with particles less than 6.4 mm. where eggs had developed nor- mally but the hatched fry were unable to emerge because of sediment. Phil lips et a1 . (1975) found an inverse relation between quantity of fine sedi- ments and fry emergence. Bjornn (1969) and McCuddin (1977) demonstrated that survival and emergence of chinook salmon and steelhead embryos were reduced when sediments less than 6.4 mm in diameter made up 20-25 per- cent or more of the substrate (figs. 19 and 20). Biornn (1969) Chinook salmon - Steelhead---- n 30- 0 ,,I,, 0 10 20 30 40 50 60 PERCENTAGE FINE SEDIMENT Figure 20-Percentage emergence of swim-up fry placed in gravel-sand mixtures. Sediments were 1- to 3-mm particles in the study by Phillips et al. (1975), less than 2 mm in the study by Hausle and Coble (1976), and less than 6.4 mm in studies by Bjornn (1969) and McCuddin (1 977). STREAMFLOW Streamflow requirements of incubating salmonid eggs are largely unknown partly because of the lack of information on interactions of surface flows and the intragravel environment. According to Stalnaker and Arnette (1976), most agencies that are concerned with fish habitat do not attempt to deal specifically with streamflows for incubation but only for spawning, on the assumption that flows suitable for spawning will be suitable for incubation. U.S. Fish and Wildlife Service personnel at times have re- commended an increase in flow for incubation over that present at spawning (Hale in Hooper 1973). Oregon Department of Table 9. General habitat guidelines for incubation of salmonid embryos Di ssol ved oxygen At or near saturation; lower threshold - 5.0 mg/l Water temperature 1 1 4"-14°C- Parameter Permeabi 1 i ty More than 1 300 cmlh Recommended limit Sediment composition Less than 25% by volume of fines 26.4 mm Surface flow Sufficient to a1 low fry to emerge Surface velocity Velocities should be 1 ess than those that scour the redds and displace spawning bed materi a1 s Apparent velocity More than 20 cmlh Biochemical oxygen demand Should not diminish or deplete the dissolved oxygen content below stated 1 eve1 s 11 Upper and lower values are threshold temperatures. Eggs will - develop normal ly at lower temperatures provided initial development has progressed to where they become tolerant of cold. Fish and Wildlife personnel use field observations to judge recommended incubation flows that are often equivalent to about two-thirds of the spawning flow. Thompson (1972), however, pointed out that the two-thirds rule does not always hold, and adequate flow depends largely on the particular stream. Research is currently underway in Idaho and Alaska to quantify the instream flow needs for suc- cessful incubation and hatching of salmonid eggs. Forest practices, such as roadbuilding and clearcut logging, may increase the water yield from a watershed and sometimes contribute to the flooding in a stream (Rothacher 1971). Rapid fluctuations in streamflow can decrease egg survival by disturbing redds and thereby crushing and dislodging eggs. Gangmark and Broad (1956) attributed complete mortality of planted chinook eggs to stream flows that increased 100 times during egg planting. Other investigators have also noted the deleterious effects of flooding on egg survival (Hobbs 1937, Neave 1953, Gangmark and Bakkala 1960, Sheridan and McNeil 1968). As noted by Chapman (1962), abnormally high flow at the wrong time causes increased mortality. Moderately high flows are beneficial in assuring adequate interchange of intragravel and surface waters and improving the oxygen supply to embryos. Because species-specific incubation criteria have not been developed, generalization is needed to define suitable incubation for anadromous sal- monids. General guidelines for salmonid incubation based on the, preceding information are presented in table 9. JUVENILE REARING Habitat requirements of juvenile anadromous fish in streams vary with species, size, and time of year. The rearing period extends from fry emer- gence to seaward migration and can range from a few days for chum and pink salmon to 3 or 4 years for steelhead trout. For fish that spend an extended time in fresh water, the quantity and quality of the habitat sets the limits on the number of fish that can be produced. Important habitat components for juvenile salmon and trout are fish food production areas, water quality and quantity, cover, and space. The interaction of some of these habitat components with bio- logical features of the envi- ronment have been studied (Giger 1973, Hooper 1973), but specific criteria for rearing habitat have not been completely defined for anadromous salmonids in streams, We will discuss features of stream habitat and relate them to salmonid pro- duction where warranted by the data available. FISH FOOD PRODUCTION AREAS Density of juvenile anad- romous salmonids may be regu- lated by the abundance of food (perhaps expressed as competi- tion for space) in some streams (Chapman 1966). Food for these salmonids comes primarily from the surrounding land and from the substrate within the stream; the relative importance of terrestrial and aquatic insects varies with stream size, loca- tion, riparian vegetation, and time of year, VELOCITY According to Scott (1958) and Allen (1959), velocity is the most important parameter in determining the distribution of aquatic invertebrates in streams. Most aquatic invertebrates live in a vertical boundary layer on the stream substrate where velocities are near zero. Water velocities just above the bound- ary layer, however, are typical of r$Ffle areas (Pearson et a, Needham and Usinger 1956, Delisle and Eliason 1961, Arthur 1963, Ruggles 1966, Kimble and Wesche 1975, and table 10). DEPTH The influence of water depth on aquatic insect pro- duction is poorly understood, but Needham and Usinger (1956) and Kennedy (1967) found the largest numbers of organisms in shallow areas typical of riffles. In a study by Kimble and Wesche (1975), mayflies (Ephemerop- tera), stoneflies (Plecoptera), and caddisflies (Trichoptera) were found in depths less than - 41 Unpublished report, "Factors affecting the natural rearing of juvenile coho salmon during the summer low flow season," by L. S. Yearson, K. R. Conover, and R. E. Sams. Fish. Comm. Oreg., Portland, 1970. Table 10-Water velocity criteria for aquatic invertebrates Kennedy (1 967), Pearson et a1 .- Surber (1 951 ) Delisle and Eliason (1961) Hooper (1973) Giger (1 973) Needham and Usinger (1 956) Kimble and Wesche (1975) Thompson (1 972) Source 1/ See text footnote 4. - Vel oci ty range 0.3 m. Hooper (1973) reported (1947) reported that, in general, that areas of highest inverte- the diversity of available cover brate productivity usual ly occur for bottom fauna decreases as in streams at depths between the size of inert substrate 0.15 and 0.9 m if substrates and particles decreases. Rubble velocities are suitable. seems to be the most productive substrate. Large rubble sub- Meters per second SUBSTRATE Stream substrate compo- sition is another factor that regulates the production of invertebrates; highest pro- duction is from gravel and rubble-size materials (Needham 1934, Linduska 1942, Smith and Moyle 1944, Sprules 1947, Ruttner 1953, Cummins 1966, Thorup 1966, Kennedy 1967, Corning 1969, Hynes 1970). Substrate size is a function of water velocity, with larger materials (rubble and boulder) associated with fast currents and smaller materials (silt and sand) with slow-moving water. Pennak and Van Gerpen (1947) noted a decrease in number -of benthic invertebrates in the progression rubble- bedrock-gravel-sand. A similar decrease was noted by Kimble and Wesche (1975) in the series rubble-coarse gravel-sand and fine gravel-silt. Sprules strate provides insects with a firm surface to cling to and also provides protection from the current. The importance of insects produced in riffles as food for fish is documented by Waters (1969), and Pearson et al. (see footnote 4) reported higher coho production per unit area in pools with large riffles up- stream than in pools with small riffles upstream. Velocity, depth, and sub- strate criteria for optimum fish food production are: Velocity 0.46-1.07 m/s Depth 0.46-0.91 m Substrate Composed largely of coarse gravel (3.2-7.6 cm) and rubble (7.6-30.4 cm) RIPARIAN VEGETATION Terrestrial insects are also important food items for salmonids. They may enter streams by falling or being blown off riparian vegetation and by being washed in from shoreline areas by wave action or rapid flow fluctuations (Mundie 1969, Fisher and LaVoy 1972). Once in the stream, these organisms are entrained by the current, become a part of the drift, and are fed upon by fish Surber 1936, Kelley et a1. ,?' Delisle and Eliason 1961, - 5/ Unpublished report, "A method Kennedy 1967, Allen 1969). Plant material that falls into the stream from riparian vege- tation may be an important source of food to aquatic in- vertebrates. Sekulich and Bjornn (1977) found that ter- restrial insects were second only to chironomids (midges) in importance as food for juvenile anadromous salmonids in the streams they studied. Groups of insects and other arthropods that may become a part of ter- restrial drift include: Diptera (flies), Orthoptera (grass- hoppers and crickets), Coleop- tera (beetles), Hymenoptera (bees, wasps, and ants), Lepi- doptera (butterflies and moths), Homoptera (leaf hoppers), and Araneida (spiders). to determine the volume of flow required by trout below dams: a proposal for investigation," by D. W. Kelley, A. J. Cordone, and G. Delisle. Calif. Dep. Fish and Game, Sacramento, 1960. WATER QUALITY Temperature Salmonids are cold water fish with definite temperature requirements during rearing. Water temperature influences growth rate, swimming ability, availability of dissolved oxygen, ability to capture and use food, and ability to with- stand disease outbreaks. Brett (1952) lists the upper lethal temperature for chinook, pink, sockeye, chum, and coho salmon as 25.1°C. The upper lethal temperature for rainbow trout lies between 24' and 29.5OC depending on oxygen concen- tration, fish size, and accli- mation temperature (McAfee 1966). Slightly lower temper- atures can be tolerated but are stressful. Bell (see footnote 1) stated that, in general, all cold water fish cease growth at temperatures above 20.3OC be- cause of increased metabolic activity. Fa1 1 chinook finger- lings had increasing percentage weight gains as temperature was increased from 10.OO to 15.7OC, and then weight decreased with a further increase in temper- ature to 18.4OC (Burrows in Bell, see footnote 1). Baldwin (1956) noted a similar relation for brook trout, with increases in percentage weight gain with increased temperature from 9.1 to 13.1°C and a subsequent decrease in percentage weight gain with temperatures exceeding 17.1°C. At 17.1°C,brook trout feeding decreased and, when temperature reached 2 1.2 OC, the fish only ate 0.85 percent of their body weight per day. By comparison, a 100-mm-long sal- monid that weighs 10 g would need to eat about 1.8 percent of its body weight each day to maintain itself and 2.5 percent to grow rapidly in 15OC water. Salmonids prefer a rather narrow range of temperature in which to live (table 11) , and temperature may help regulate density. In laboratory stream channels, Hahn ( 1977 ) found twice as many steelhead fry remained in channels with daily fluctuating (8O-19OC) or con- stant 13.5 OC water temperatures than in a channel with constant 18.5OC water. Fry density in a channel with constant 8.5 OC water was double that in chan- nels with constant 13.5OC or fluctuating temperatures. Water temperatures in a particular stream vary seasonal ly, tem- poral ly, and spatially ( for example, between forested and nonforested areas). Seasonal and temporal changes are largely out of human control; certain land-use practices (for example, channelization or removal of shade trees), however, can change the temperature in sec- tions of streams. If riparian vegetation is removed, exposing the stream to direct sunlight, water temperatures usually increase in summer (Greene 195 0, I I I ---------------------"C---------------------- - Chinook 7.3-14.6 q12.2 25.2 Coho 11.8-14.6 3'20.0 25.8 Chum 11.2-14.6 y13.5 25.8 Pink 5.6-14.6 10.1 25.8 Sockeye 11.2-14.6 y15.0 24.6 Steel head '7.3-14.6 10.1 24.1 Cutthroat 9.5-12.9 -- 23.0 Brown 3.9-21.3 -- 24.1 Table I1 -Preferred, optimum, and upper lethal temperatures of various salmonids (from Bell 1973 unless otherwise noted) 1/ From Bell (see text footnote 1). / - From an unpubl ished report, "Fish health and Management: concept and methods of aquaculture," by G. W. Klontz, Univ. Idaho, Moscow, 1976. 31 From Brett et al. (1958). / - From Garside and Tai t (1958). Chapman 1962, Gray and Edington 1969, Meehan 1970, Narver 1972, Moring and Lantz 1974, Moring 1975 ) . Colder winter temper- atures may result from loss of canopy and adversely affect egg incubation (Greene 1950, Chapman 1962). r Species DISSOLVED OXYGEN Preferred temperature range I The concentration of dis- solved oxygen in streams is important to salmonids during rearing. At temperatures above 15OC, concentrations of dis- solved oxygen regulate the rate of active metabolism of juvenile sockeye salmon (see footnote 1). Fry (1957) proposed that where the oxygen content became un- suitable, the active metabolic rate decreased. Rainbow trout swimming speeds were reduced 30 and 43 percent when oxygen was reduced to 50 percent of satu- ration at temperatures of 21'-23OC and 8'-10°C, respec- tively (Jones 1971). Growth Optimum temperature rate, food consumption rate, and the efficiency of food utili- zation of juvenile coho salmon all declined when oxygen was 4 or 5 mg/l (Herrmann et al. 1962, and figs. 21, 22, and 23). Upper lethal temperature Juvenile chinook salmon avoided water with oxygen concentrations near 1.5-4.5 mg/l in the summer, but reacted less to low levels in the fall when temperatures were lower (Whitmore et al.1960). In a review paper, Davis (1975) examined information on incipient oxygen response thresh- olds for salmonids (table 12), and developed oxygen criteria with three concentrations (table 13). At the highest concentration, fish had ample oxygen and could function with- out impairment. At the middle concentration, the average member of a species begins to exhibit symptoms of oxygen 1956 tests O1 1955 tests .O Surviving fish AA Only or mostly dying fish 1 80- 2 Y t; + 60- (3 $ 40- f 4 20- Y3 - 2 0- f U YI a -20- -40- Figure 21 -Weight gains (or losses) in 19 to 28 days among frequently fed age-class 0 coho salmon, expressed as percentages of the initial weight of the fish, in relation to dissolved oxygen concentration. The curve has been fitted to only the results of tests performed in 1956. All of the 1956 positive weight-gain values are results of 21-day tests (from Herrmann et al. 1962). &A I I 1 r I 1 I Or 1956 tests (Y 1955 tests .O Surviving fish AA Only or mostly dying fish l 23456789 OXYGEN CONCENTRATION (MILLIGRAMS PER LITER) OXYGEN CONCENTRATION (MILLIGRAMS PER LITER) Figure 22-Grams of food (beach hoppers) consumed by frequently fed ageclass 0 salmon per day per gram of initial weight of the fish, in relation to dissolved oxygen concentration. The curve has been fitted to only the 1956 data (from Herrmann et al. 1962). distress; at the lowest concen- tration, a large portion of the fish population may be affected. Dissolved oxygen concen- trations are normally near 0 Or 1956 Tests 06 1955 Tests Surviving fish AA Only or mostly dying fish OXYGEN CONCENTRATION (MILLIGRAMS PER LITER) Figure 23-Food conversion ratios for frequently fed age- class 0 coho salmon, or their weight gains in grams per gram of food (beach hoppers) consumed, in relation to dissolved oxygen concentration. A food conversion ratio of zero (not a ratio having a negative value) has been assigned to each group of fish that lost weight. The curve has been fitted only to the 1956 data (from Herrmann et al. 1962). saturation, except in small streams with large amounts of debris from logging or other sources (Hall and Lantz 1969) or in larger, slow-moving streams receiving large amounts of municipal or industrial waste. SUSPENDED AND DEPOSITED SEDIMENT Suspended and deposited fine sediment can adversely affect salmonid rearing habitat if present in excessive amounts. High levels of suspended solids may abrade and clog fish gills, reduce feeding, and cause fish to avoid some areas (Trautman 1933, Pautzke 1938, Smith 1939, Kemp 1949, Wallen 1951, Cooper 1956, Bachman 1958, Cordone and Kelley 1961). According to Bell ( see footnote I), streams with silt loads averaging less than 25 mg/l can be expected to support good freshwater fish- eries. State turbidity standards for Colorado, Wyoming, Montana, and Oregon are set at no more Table 12-Incipient oxygen response thresholds for various salmonids (modified from Davis 1 975)" Arctic char Brown trout Brook trout Species Rainbow trout Rainbow trout Holeton (1973) Irving et al. (1941) Irving et al. (1941) Graham (1949) ,I 0, I Beamish (1964) Irving et al. (1941) Response Randall and 120-250 g 8.5-15 5.18-7.34 Smith (1967) Downing (1954) 13.3 + 1.4 17 + .5 9.74 Source cm Jones (1971) 20 mo. old 8-10 5.94-5.67 ,I I 20 mo. old 21-23 4.50-4.34 I tazawa (1970) 235-510 g 2.3-13 8.73-6.74 Size Temperature Kutty (1968) -- 15 5.08 Randall and - - 15 5.18-6.47 Smith (1967) Hughes and Saunders 400-600 g 13.5 5.35 (1 970) Cameron (1 971 ) 300 g 10, 15, 20 4.71-5.75 Lloyd (1961) 1-11 g 17.5 5.78 Oissolved oxygen Sockeye salmon Brett (1964) 50g 20-24 9.17-8.53 Concentration Coho salmon Saturation Davis (1973) 1579g 13 6.74 Randall and 1.5-1.7 kg 15 5.07 Smith (1967) Whitmore et al. (1960) 6.3-11 cm -- 4.5 Hicks and 5.1-14.8 m 12 + 1 9.0 DeWitt (1971) Davisetal.(1963) Juvenile 10-20 11.33-9.17 Oahlberg et al. (1968) " 20 9.17 Herrmann (1958) I 8.0-4.0 Chinook salmon Whitmore et al. (1960) 6.3-11 cm summer temp. 4.5 " 6-3-11 cm fall temp. 4.5 Davis et al. (1963) Juvenile 10-20 11.33-9.17 Atlantic salmon Kutty and 87-135 g 15 4.5 Saunders (1 973) Percent 15.8 Signs of asphixia and loss of equilibrium 50 Blood not fully saturated with O2 below this level 50 ,I 63.2 Onset of 02-dependent metabolism 50.7 Reduced cruising speed 98.8 Onset of 02-dependent metabolism 7 5 Reduced activity all temperatures Standard oxygen uptake reduced below this level Below this level, blood is not fully saturated with oxygen Circulatory changes occur, including a slowing of the heart Any reduction in oxygen led to more rapid death in cyanide 43 percent reduction in maximum swimming speed 30 percent reduction in maximum swimming speed Blood not fully saturated with O2 below this level Altered respiratory quotient, little capacity for anaerobic metabolism below this level Changes in oxygen transfer factor and effectiveness of O2 exchange occur Breathing amplitude and buccal pressure elevated Blood not fully saturated with O2 below this level Toxicity of zinc, lead, copper, phenols increased markedly below this level Available oxygen level appears to limit active metabolism and maximum swimming speed 63.6 Blood not fully saturated with O2 below this level 50 Elevated blood and buccal pressure, breathing rate increased -- Erratic avoidance behavior 83.1 Acute mortality in kraft pulpmill effluent increased below this level 100 Reduction of O2 below saturation produced some lowering of maximum sustained swimning speed 100 I ,I 87.2-43.6 Growth rate proportional to oxygen level with best growth at 8.0 mg/l, lowest at 4.0 mg/l Marked avoidance of this level in sumner Little avoidance of this level in fall 100 Reduction of O2 below saturation lowered maximal sustained swimning speed 44-33 Salmon stop swimning at a speed of 55 cm/s at O2 levels below this; faster swimming requires more oxygen 1'courtesy of the Journal of the Fisheries Research Board of Canada. Table 13-Response of freshwater salmonid populations to three concentrations of dissolved oxygen (modified from Davis 1975, courtesy of the Journal of the Fisheries Research Board of Canada) Function without impairment 7.75 76 76 76 76 85 93 Response Initial distress symptoms 6.00 57 57 57 59 65 72 Most fish affected by lack 4.25 38 38 38 42 46 51 of oxygen Mg/l ---------- Percent---------- Oxygen than 10 JTU, 10 NTU, 5 JTU and 5 NTU over background levels, respectively. g/ Saturation at gi ven temperatures ( "C) 0 5 10 15 20 25 Cordone and Kelley (1961) suggest that indirect rather than direct effects of too much fine sediment damage fish populations. Indirect damage to the fish population by destruc- tion of the food supply, lowered egg or alevin survival, or changes in rearing habitat probably occurs long before the adult fish would be directly 7/ harmed (Ellis 1936, Corfitzen,- , -- - JTU = Jackson turbidity units. NTU = Nephelome tric turbidity units. - 7/ Unpublished mimeographed report, "A study of the effect of silt on absorbing light which promotes the growth of algae and moss in canals," by W. D. Corfitzen. U.S. Dep. Int., Bur. Reclam., 1939. Sumner and ~rnith,g/ Tebo 1955, 1957, 1974, Tarzwe1194957, Ziebell 1957, Casey,- Bartsch 1960, Cordone and Pennoyer,s/ Chapman 1962, Bjornn et al. 1977). - 8/ Unpublished mimeographed report, "A biological study of the effects of mining debris dams and hydraulic mining on fish life in the. Yuba and American Rivers in California," by F. H. Sumner and 0. R. Smith. Submitted to the U. S. District, Eng. Office, Sacramento, California, from Stanford Univ., 1939. - Unpublished mimeographed report, "The effects of placer mining (dredging) on a trout stream," by 0. E. Casey. Annu. Prog . Rep. , Proj . F-34-R-1. Water Quality Investigations, Federal Aid in Fish Restoration, Idaho Dep. Fish and Game, Boise, 1959. - lo/ Unpublished mimeographed report, " Notes on silt pollution in the Truckee River drainage," by A. J. Cordone and S. Pennoyer. Calif. Dep. Fish and Game; Inland Fish Admin. Rep. , Sacramento, 1960. Deposited sediment may reduce available summer rearing ( fig. 24) and winter holding (fig. 25) habitat for fish (Stuehrenberg 1975, Klamt 1976, Bjornn et al, 1977)- Bjornn et al. (1977) added fine sediment (less than 6-4 mm in diameter) to natural stream channels and found juvenile salmon abundance decreased in almost direct proportion to the amount of pool volume lost to fine sediment ( fig . 2 6 ) . Because sediment budgets are difficult to deter- mine for each stream, Bjornn et ale recommended using the per- centage of fine sediment in selected riffle areas as an index of the "sediment health" of streams. They reasoned that if the riffles contained neg- ligible amounts of fine sedi- ment, then the pools and inter- stitial spaces between the boulders of the stream substrate would also have negligible amounts of sediment. Control I without sediment \ n Test with sediment) M TEST NO 10 12 11 16 13 13 13 14 15 SPECIES-ACE CKO CKO SHo SHo CKO SHo CKOSHO CTO CT1,? ORIGIN W W H H W H W H H W Figure 24-Densities of fish remaining in artificial stream channels after 5 days during winter tests, 1975: W = wild; H = hatchery; 1/2 = boulders in pools 1/2 imbedded with sediment; F = fully imbedded; CK, = age 0 chinook salmon, SH, = age 0 steelhead trout; CT, = age 0 cutthroat trout, CT,.2 = age 1 cutthroat trout (from Bjornn et al. 1977). Control (without sediment) Test (with sediment) TESTY01 1 3 4 6 5 7 8 SPECIES -AGE SH1 SH1 sH1 SHo SHo SHo CKO CKO O~U~IN~-WILD~HATCHERY-~ WILD IUDEDDEDNESS 113 2/3 F F 112 F 1/2 F Figure 25-Densities of fish remaining in the Hayden Creek artificial stream channels after 5 days during the summer tests, 1974 and 1975: SH, = age 1 steelhead; CKo age 0 chinook; 1/3 = key boulders in pools 1/3 imbedded with sediment; F = key boulders in pools fully imbedded (from Bjornn et al. 1977). 0 I I I 1 0 2 5 50 75 100 PERCENTAGE POOL AREA Figure 26-Fish numbers in upper test pool versus percentage pool area deeper than 0.30 m, during the sediment additions into Knapp Creek, 1973 and 1974. Arrows denote observations not used in fitting the regression line. P = prior to addition of sediment; 1 = after first addition; 2 = after second addition; 3 = after third addition (from Bjornn et al. 1977). COVER Cover is perhaps more important to anadromous sal- monids during rearing than at any other time, for this is when they are most susceptible to predation from other fish and terrestrial animal s . Cover needs of mixed popula-kions of salmonids are not easily deter- mined (Giger 1973). Shelter needs may vary diurnally (Kalle- berg 195 8, Edmundson et a1 . 1968, Allen 1969, Chapman and Bjornn 19691, seasonally (Hartman 1963, 1965, Chapman 1966, Chap- man and Bjornn, 1969), by species (Hartman 1965, Ruggles 1966, Allen 1969, Chapman and Bjornn 1969, Lewis 1969, Pearson et al. (see footnote 4 ) , Wesche 1973, Hanson 1977), and by fish size (Butler and Hawthorne 1968, Allen 1969, Chapman and Bjornn 1969, Everest 1969, Wesche 1973, Hansori 1977). Overhead cover--riparian vegetation, turbulent water, logs, or undercut banks--is used by most salmonids (Newman 1956, Wickham 1367, Butler and Haw- thorne 1968, Baldes and Vincent 1969, Bjornn 1969, Chapman and Bjornn 1969, Lewis 1969, Lister and Genoe 1970, Wesche 1973). Beside providing shelter from predators, overhead cover pro- duces areas of shade near stream margins. These areas are the preferred habitat of many juve- nile salmonids (Hartman 1965, Chapman 1966, Allen 1969, Everest 1969, Mundie 1969, Everest and Chapman 1972). Submerged cover--large rocks in the substrate, aquatic vegetation, logs, and so on--is also used by rearing salmonids. Hoar et al. (1957) and Hartman (1965) observed that newly emerged salmonids tend to hide under stones. Similar behavior is typical of overwintering juvenile steelhead and chinook that seek refuge within rock and rubble substrate in Idaho streams (Chapman 1966, Chapman and Bjornn 1969, Everest 1969, Morrill and Bjornn 1972). The relative importance of cover is illustrated by experi- ments in which salmonid abun- dance declined when cover was reduced (Boussu 1954, Peters and Alvord 1964, Elser 1968) and in experiments where salmonid abundance increased when cover was added to a stream (Tarzwell 1937, 1938, Shetter et al. 1946, Warner and Porter 1960, Saunders and Smith 1962, Chapman and Bjornn 1969, Hunt 1969,1976, Hahn 1977, Hanson 1977). STREAMFLOW Recommended streamf lows for rearing habit at have usually been based on the individual components (such as food, cover) of habitat rather than numbers or biomass of fish. Thompson (1972) listed guidelines for developing streamflow recom- mendations in rearing habitat: e adequate depth over riffles riffle/pool ratio near 50:50 approximately 60 percent of riffle area covered by flow riffle velocities of 0.31- 0.46 m/s e pool velocities of 0.09- 0.24 m/s stream cover available as shelter for fish. Such guidelines are obviously based on the food production, cover, and microhabitat needs of fish, rather than the relation between streamf low and fish production. Streamf low has been related to cover (Kraft 1968, 1972, Wesche 1973, 1974, and figs. 27, 28, and 29); streamflow and pool area to standing crop of fish (Kraft 1968, 1972, Nlckel- son and Reisenbichler 1977, and fig . 30) ; standing crop to cover (Wesche 1974, Nickelson and Reisenbichler 1977, and figs. 31 and 32) ; and standing crop to a habitat quality index (Nickelson 1976, and fig. 33). Such studies suggest a definite relation between stream carrying capacity for fish and discharge. 00: PERCENTAGE BASE FLOW Figure 27-Comparison of percentage reductions of fish numbers and cover in three runs in Blacktail Creek, Montana (data from Kraft 1968, from White 1976). lO0l t ? i Douglor Creek #I: Hog Pork Creek j MEAN COVER RATING Hog Pork Creek Douglas Creek #7 X Douglas Creek #1 PERCENTAGE AVERAGE DAILY FLOW Figure 29-Comparison of percentage of habitat reduction with percentage decrease in average daily flow and hypothetical percentage decrease in fish population (data from Wesche 1974, from White 1976). 4b SO 60 70 80 1 POOL VOLUME (CUBIC METERS) Figure 30-Relation between pool volume and juvenile coho standing crop (from Nickelson and Hafele 1978). Figure 28-Changes observed in the mean trout-cover rating as flow was reduced at the Douglas Creek No. 1,7, and Hog Park Creek study areas (from Wesche 1974). COVER X AREA Figure 31-Relation between mean trout cover ratings and standing crop estimates of trout at eleven study areas (from Wesche 1974). Douglas Creek #6 7 Hog Park Creek / Douglas Creek #1 / 40 Deer Creek #2 20 10 Deer Creek #1 Log Y = 0.0204 + 5.338 X 0 0.1 0.2 0.3 0.4 0.5 MEAN COVER RATING Figure 32-Relation between cover times area and cutthroat trout standing crop in two Oregon coastal streams (from Nickelson and Reisenbichler 1977). HABITAT QUALITY INDEX Figure 33-Relation between a habitat quality index and coho salmon biomass in six Elk Creek study sections at flows of 3.00, 2.25, and 1.50 ft3/s (from Nickelson 1976). SPACE Space requirements of juvenile salmonids in streams vary with species, age, and time of the year and are probably related to abundance of food (Chapman 1966). The inter- actions and relation between cover, food abundance, and microhabitat preferences of the various species of salmonids are not well understood; until they are, spatial needs of the fish will be less than adequately defined. From measurements of fish densities in streams, we have some idea of spatial require- ments of juvenile salmonids. Pearson et al. (see footnote 4) Nickelson and Reisenbichler (1977), and Nickelson and Hafele (1978, and fig. 30) found that coho standing crop was directly related to pool volume. Bjornn et al. (1977) found a similar relation for chinook salmon in small streams (fig. 26). Pear- son et al. found a close relation between total stream area and coho numbers--perhaps an example of the idea that more space equals more food equals more fish. Food and space are thought to be the most important factors influencing fish density in streams (Larkin 1956, Chapman 1966). Studies in California by Burns ( 1971) revealed signi- Cicant correlations between living space and salmonid.biomass; decreased living space resulted in increased fish mortality. Not surprisingly, the highest mortality was associated with the summer low flow period. The studies of Kraft (1968, 1972 and fig. 27) and Wesche (1974, and fig. 29) lend support to the concept that reductions in discharge decrease living space and thus decrease numbers and biomass of salmonids. Changes in streamf low influence velocities and area of riffles more than area of pools. Giger (1993) suggested that if set spatial demands are the primary regulators of fish density in pools, then increas- ing the flow in streams may not lead to increased abundance. He accepts the logic of Chapman's (1965) idea that spatial require- ments of fish control their density below ceilings set by the scpply of food. Chapman (1966) suggested that salmonids have a minimum spatial require- ment that has been fixed over time by the minimum food supply. Space needed by fish in- creases with age and size. Allen (1969) assembled data on densities of salmonids in streams and found positive correlations between area per fish and age or length (figs, 34 and 35). Additional data on densities of salmon and trout with age, size, and locality are presented in table 14 and figure 36. Allen concluded from the data he examined that densities of 10-cm salmonid9 averaged2 about 0.17 fish/m (1.7 g/m ). Residents Migrants A Chum and pink salmon A v Coho salmon v 0 Atlantic salmon 8 Brown trout o Rainbow trout Brook trout 0 Observed territory Figure 34-Average area per fish (on a logarithmic scale) against age (from Allen 1969). Brook trout 0 Observed territory LENGTH (CENTIMETERS) Figure 35-Average area per fish against length on logarithmic scales (from Allen 1969). Table 14-Densities of salmon and trout in streams Yr/cm M~ M~ egg-alevin 0.001 1000 Species Pink salmon B.C. Washington A1 as ka Age/ size Hunter (1959) Bliss and Heiser (1967) Hoffman (1965) B.C. Alaska B.C. B.C. Washington B.C. B.C. Oregon Oregon Areal fish Hunter (1959) Merrell (1962) Mckett (1958) Hunter (1959) Bliss and Heiser (1967) Hunter (1959) Wickett (1958) Chapman (1965) Chapman (1965) 0+/ 2 .33 3.0 egg-alevin .001 1000 Fish/ area Chum salmon Coho salmon alevin Weight/area Hunter (1959) B.C. B.C. Wickett (1951) Oregon Hall and Lantz (1969) Reference Stream size or flow rate 2.9 .37 - - Avg. flows: range, 41.6-183 ft3 (1.92-4.28) (.26-.52) .74 1.35 12.9 Median 4-5 m 1.69 .59 5.4 6-10 m Comnents Chinook salmon Idaho, est. of summer rearing capacity 4 streams in Idaho Idaho 4 streams in Idaho Idaho, est. of summer rearing capacity Bjornn (1978) (.59-3.301) (1.70-.30) (6.4-.86) Flows range 0.107-1.3 m3/s Sekulich and Bjornn (1977) Bjornn et al. (1977) Bjornn et al. (1974) Bjornn (1978) Chinook salmon Steelhead trout .93 1.08 6.1 Medium, width about 4-5 m 1.43 .70 3.2 " 1.92 .52 3.0 Medium, width about 6-10 m 16.67 .06 4.3 Medium, 4-5 m 5.88 .17 13.0 Medium, 6-10 m 4 streams in Idaho Bjornn et al. (1974) )I ,, " Hanson (1977) ,I 4, I, I, 6.67 .15 " - - 3.88 .258 " " Small 4.35 .23 -- Medi urn 14.49 .069 - - II I! Idaho average Graham (1977) 26.14 .038 -- Large (m/fish) (fish/m) (Lochsa River) densities for three sections; low densities result from low spawning escapements Table 14-Densities of salmon and trout in streams -(Continued) Yr/cm Steelhead salmon I+ Species Atlantic salmon Brown t roo t M~ - 109.89 (m/f ish) 60.06 (m/fish) 23.47 (m/fish) 17.84 Reference Age/ size Large (Lochsa River) (cont. from previous page) Graham 1977 Large (Selway River) " I, ,I Area/ fish Small tributaries Idaho, trib. of Lochsa R. " " Idaho, trib. of Selway R. " Fish/ area a Small I, ,I I, I, I4 , Idaho, densities are those " )I present in the fall after stocking in early spring Large (Lochsa River) Idaho, avg. density for " Comnents Weight/area " 3 sections Stream size or flow rate Small (trib. streams) 8, L, $8 Flow - 0.27--.56 cms Densities are those present " during July-August in the fall after stocking in early spring Flow - 0.59-0.95 cms I, ,I 8, ,I Small streams Scotland, densities are Mills (1969) those present in the fall " $I " after stocking in early " I, " spring I, II 1, I, II Small streams I, ,I 0, $1 I, a, Scotland, densities are those present in the fall after stocking in early spring I, Mills (1969) I It I ,I Il 40 I I, I, ,I Mean width 0.9 m England, small, headwater LeCren (1969) 2.2 m streams I, ,I 3.0 m I I, II I 3.7 m , I, ,, ,I I 2.5 m I, I, ,I 6.6 m I, I, 0, I1 .9 m ,I I, ,I 2.2 m I, 1, I, 3.0 m I 8, (I $1 # 3.7 m ,I I, I, 2.5 m I, I, I, I, I, 6.6 m I, I, I* 00 Small, widths range 0.6- Densities are averages of Mil 1s (1969) 1.5 m, avg. 1.0 m 4 stream sections I, I, 0 0, ,I 9, I, ,I Scot1 and I# )I lo England LeCren (1965) I a, England Horton 1961 I( It California Needham, et al. (1945) ,I ,I New Zealand Allen (1951) On , England Horton (1 961 ) )I I New Zealand Allen (1951) a, In New Zealand Allen (1951) Densities of age-0 trout and salmon at the end of their first summer (70-120 mm iq length) average about 5 m of stream per fish (mode about 2 m ). After 2 years of re3ring, densities averaged 2-16 m /qish, and for larger fish, 15-27 m / fish (fig. 36). The spread in densities portrayed in figure 36 results partly from differences in natural or artificial stock- ing rates, size of stream, and habitat quality. Juvenile salmonids usually occupy sites in streams referred to as "focal points" from which they venture out to perform other functions (Wickham 1967 ) . Characteristics of these focal points in water velocities, water depths, substrate, and cover represent the microhabitat preferences of the fish (table 15) to remain oriented into the a Steelhead - rainbow r Brown trout o Coho Chinook x Atlantic salmon AAA .. Figure 36-Densities of age 0, I, II, and older salmon and trout in streams usuaily after 1, 2, 3, or more summers of growth, respectively (see table 14 for sources of data). Table 15-Depth, velocity, and substrate microhabitat preferences of salmonids in streams Species Reference Age Depth Velocity Substrate Steel head Everest and Chapman (1972) ,I 11 Hanson (1977) 1, I, Stuehrenberg (1975) I, I, Chinook Thompson (1 972) Everest and Chapman (1972) Stuehrenberg (1 975) I, 11 Coho Thompson (1972) ' Pearson et a1 .y Thompson (1972) Nickelson and Reisenbichler (1977) Cutthroat Thompson (1 972) Hanson (1977) #I I4 M - <0.15 .60-. 75 .51 mean .58 " .60 " <.30 >.I5 .18-.67 .15-.30 <.61 <.61 .30-1.22 -- .30-1.22 7.30 .40-1.22 .51 mean .56 " .57 " .54 " M/ s - 10.15 .15-.30 .10 mean .15 " .15 " .14 (range .03-.26) .16 (range .05-.37) .6-. 49 <.I5 .09 (range .O-.21) .17 (range .05-.38) .06-.24 .09-.21 .05- .24 <. 30 Cm - Rubble Rubble 10-30 10-30 10-30 Silt .6- .49 -- .10 mean 5-20 .14 " 5-30 .20 " 5-30 .14 " 30 See text footnote 4. 39 current (Baldes 1968). 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Within this overall mission, the Station conducts and stimulates research to facilitate and to accelerate progress toward the following goals: 1. Providing safe and efficient technology for inventory, protection, and use of resources. 2. Developing and evaluating alternative methods and levels of resource management. 3. Achieving optimum sustained resource productivity consistent with maintaining a high quality forest environment. The area of research encompasses Oregon, Washington. Alaska, and, in some cases, California, Hawaii, the Western States, and the Nation. Results of the research are made available promptly. Project headquarters are at: Anchorage, Alaska La Grande, Oregon Fairbanks, Alaska Portland, Oregon Juneau, Alaska Olympia, Washington Bend, Oregon Seattle, Washington Corvallis, Oregon Wenatchee, Washington Mailing address: Pacific Northwest Forest and Range Experiment Station 809 N. E. 6th Ave. Portland, Oregon 97232 -- - -- ~ - - - - -- - . --- - - I 1, The FORE ST SERVl iilture is dedicated to the principle of on's forest resources for sustained vie fe, and recreation. l and private forest nal Grasslands, it greater service to 1 11 i 1 I The U.S. Depart equal consideration 111 Applicants for al 1, l1 -~ - . - - - - ~ - - - ---- - t programs will lor. sex. reliclior )f the N Dna uril