Old-Growth Forests

c.i5 Fishand WildlifeRelationships in Old-GrowthForests Proceedingsof a Symposium Sponsoredby Alaska District, American Institute of FisheryResearch Biologists Northwest Section, The Wildlife Society AlaskaCouncil on Scienceand Technology Held in Juneau,Alaska, 12-15 April 1982 Symposium Editors William R. Meehan TheodoreR. Merrell,Jr. ThomasA. Hanley SuggestedCltatlon: (Eds.). 1984. Fish and ttilliam R., TheodoreR. Merrell, Jr. and Thornas^A' Hanlev lleehan, in Juneau,Alaska' ltiiaiiie-ietaiionstrips in 0ld-GrowthForests: Proceedingsof a syrnpoiiumheld 12-15April 1982. Ainer.Inst. Fish. Res.Biol' 425p' Published by the American lnstitute of Fishery Research Biologists December 1984 Availablefrom John W. Reintjes,Rt. 4, Box 85, MoreheadCity, NC 28557 Price920. *'"' &,,4 HABITATSAND SALMONIDDISTRIBUTION IN PRISTINE. E SEDIMENT-RICHRIVER VALLEY SYSTEMS: S. FORKHOH AND .€ ii OUEETSRIVER, OLYMPIC NATIONAL PARK € E JamesR. Sedell I USDA, ForestService. Corvallis, Oregon il ri Joseph E. Yuskaand RobertW. Speaker Oregon State University,Corvallis, Oregon :]: ABSTRACT Four distinct running-water habitats are defined and examined on the South Fork Hoh River and Upper Queets River-main river channel, river off-channel areas, terrace tributaries, and valley-wall tributaries. Speciescompositions, densities, and total fish biomassesare distinctly different for each habitat examined. Habitat formed by the main river channel and its tributaries is controlled by the valley terrace structure and the modifyingeffects of large woody debris. Large woody debris is important to all habitats regardless of size of stream. Without large wood, spawning and rearing-habitat quality would be poorer, even in the large, sediment-rich main channel. large wood-capped side channels had eight times the coho salmon (Oncorhynchus kisutch) densities as side channels without debris. During late summer, the majority of juvenile salmonid rearing occurs in river side-channelareas and tributaries. INTRODUCTION Stream ecologists have few benchmark descriptive terrace tributaries. and vallev-wall tributaries (Swanson studies for naturally sediment-rich river systems. We and Lienkaemper 1982; et ;1. lg82; Sedell et'al.1982). know very little about aquatic habitats and how they are Speciescompositions, densities,and total fish biomasses formed in pristine, sediment-rich river valley systems.We were defined for each habitat type. With each habitat also know very little about how a pristine old-growth type, pools were described and the role of large woody forest interacts with the river to produce different fish debris in the formation and stability of fish habitats was habitats. documented. Sedell et al. (1982) found terrace The rivers of the Olympic National Park representthe tributaries and side channels to have the higheststanding last pristine coastal systems of intermediate size in the crops of juvenile coho salmon. This present study western United States. As such, they can provide reexamined the sites on the South Fork Hoh River and important insights as to the summer salmonid habitats of examined the Upper Queets River in order to determine coastal rivers in their "native condition." For these whether the 1978 results were consistent through time rcasons, a description of two rivers in the Olympic (South Fork Hoh River) and held true for another river National Park provide a neededand significant baseline system (Upper Queets River). for streamecologists and fisheriesmanagers in the Pacific We thank Jeff Cederholm and Peter Bisson for Northwest. reviewing the draft manuscript. Our heartiest thanks to The 1978 South Fork Hoh River study examined late Judy Bufford for drawing the figures, and to Rose Davies summer frsh populations in relation to four general and Phyllis Taylor-Hill for typing the manuscript. habitat types: main riverchannel, river off<hannel areas, HABITAT DESCRIPTIONS Geomorphic processeshave created and maintained Main River Channel four broadly defined classesof aquatic habitat in the South Fork Hoh River and Upper Queets River valleys The main river channelsfor both the Queets River and (Swanson and Lienkaemper 1982). These are the main South Fork Hoh River (Sedell et al. 1982\are wide and channel, side channel or off<hannel areas, terrace shallow. Wetted widths range from 8 to l0 m in summer tributaries, and valley wall tributaries. The influencesof to 20 to 40 m in winter. The main channel meanders forest vegetation on aquatic ecosystemsand geomorphic within a wide channel ofexposed gravel bars that average forms and processesincrease across this range ofstream 100 m wide. The large cobble substrate appears very types from main river channel to valley wall tributary. stable, with gravel bars being formed and destroyed Structure and productivity of aquatic communities continuously. Some bank cutting is evident along the vary acrossthese stream types in responseto geomorphic steep south valley side slope. The water is turbid due to factors and degree offorest influence (Sedell et al.1982; suspendedglacial material. Organic material transfer and Ward et al. 1982). storage is low. Edges of the main channel accumulate 33 &- sediments but riffle areas are relatively clean. The Terrace Tributaries channel gradient is 2-3 percentand is composed mainly of riffles and deeper runs, with some pools associatedwith Terrace tributaries result from spring networks on the debris. Riparian vegetation does not significantly flat valley floor and from tributaries draining the valley influence the course of the river; however, bank cutting side-slopesand continuing acrossthe terracesto the main causes inputs of large woody debris which can river on the South Fork Hoh River. Many terrace accumulate on bars and outsides of bends to deflect the tributaries parallel the secondary river channels that cut river flow (Swanson and Lienkaemper 1982). Debris through the lower terrace areas within the flood plain accumulations provide little cover for fish rearing in the before emptying into the main river. These streams are main river channels, but divert water through side- very stable and have low gradients, slow velocities, and channel overflow areas. Chinook salmon spawning channel widths from I to 5 m. These features are *wall habitat is provided by the big root wads and boles sometimes referred to as based streams." This functioning as scour agentsin the main channel. The tail- results from mainstream overflow of natural stream outs of these scour pools provide excellent cleaned and leveesin combination with collected side-slope runoff. sorted gravels. This habitat type is common in both glacial and non- glacial high-gradient streams. Where sediments have been deposited historically, this habitat type is often Side-Channel or Off-Channel Areas poorly developed and is usually considered a side- Side channelsare subsidiary channelsto the main river channel feature. ln glacial streams such as the Hoh and which are located within the active exposed lower flood Queets River systems,these features are well developed. plain. These channels are not the obvious braided The lower Mississippi River has a few of these terrace channels. Unlike a braid, they carry a very small systemsthat are 28-320km long and9Gl26km wide, e.g. percentage of the flow of the main channel. Some are Yazoo River Basin. caused by woody debris accumulations on bars in the Terrace tributaries were found to be the most main channel; river flow is diverted by debris through a homogeneous of the habitats examined. Most terrace cobble and gravel flood levee.Some sidechannels are the tributaries along the Upper Queets River appear to be result of channel migration of the point bar. As the spring- and seepage-fed, low-gradient streams. channel migrates it often leavesan array of "scroll bars" Generally, they arise from a marshy or spring area where or levees which are generally parallel with the main the terrace meetsthe side slope, and flow parallel to the channel and not long in length (P. Peterson, personal main river for a considerable distance before joining the communication). Water percolates through the flood main river. Terrace tributaries have a very small levee gravel berm and debris to create a side channel watershed and never had low-velocity flows running between the gravel berm and the bank opposite the main through them year:round. Depending on their distance river flow channel. Other off-channel areas are from the main river, terrace tributaries are affected by intermittent overflgw channels that receivegroundwater main channel floods in different ways, but do not scour as from the main rivei and nearby terrace. Moit are subject side channels often do. In most cases,terrace tributaries to direct flows during freshet periods; others become receive depositional "pulses" from main-river flood completely isolated during summer low-flow periods. flows, to the extent that the flood level of the main river Flow velocities are lower than the main river and water penetratesthe terrace tributary system. percolated through berm gravels carries reduced Terrace tributaries are composed predominantly of suspended sediment. Organic input from terrace pools and short sectionsof riffle. Pools accumulate large vegetation and overflow accumulations from main river amounts of riparian leaf litter from the dense forest floods collect on off-channel pool bottoms. In the canoopy, thus producing abundant aquatic insects absence of heavy shading and the scouring effects of (Ward et al. 1982). Pool substrate is

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