Seattle’s Aquatic Environments: Duwamish Estuary

Duwamish Estuary The following write-up relies heavily on the Case Study of Elliott Bay and the Duwamish River Estuary by John Houghton, Pentac Environmental, in the State of the Nearshore Ecosystem: Eastern Shore of Central Puget Sound, Including Vashon and Maury Islands (WRIAs 8 and 9). January 2001 (Review Draft) for the WRIA 8 and 9 Nearshore Technical Committee.

Overview The Duwamish River estuary is located at the tide. During periods of low fresh-water inflow and lowermost extent of the Green/Duwamish River high tide stage the salt-water wedge has extended as system (WRIA 9), a 93 mile long river system that far upstream as the Foster Bridge, 10.2 mi above originates in the Cascade Mountains near Stampede the mouth. At fresh-water inflow greater than Pass and flows generally west and northwest 1,000 cfs the salt-water wedge does not extend toward the city of Seattle. Currently, the Green/ upstream beyond the East Marginal Way Bridge Duwamish River basin drains 483 square miles (RM 7.8) regardless of the tide height (Stoner 1967). (Weitkamp et al. 2000). Tidal influences are observed upstream to about the mouth of the The Duwamish River transports fine material in a Black River in the city of Tukwila. These last 11 freshwater plume emptying into Elliott Bay. miles of the system are a brackish estuarine envi- Sediments return from Elliott Bay to the Duwa- ronment called the Duwamish estuary. The mish as a near-bottom sediment load contained in Duwamish is considered “vital to salmon as a the salt-water wedge (GeoSea Consulting 1994). transition area for adaptation of migrants to Eight species of anadromous salmonids have been salinity changes.” (Williams et al. 1975). The last noted in the Duwamish Estuary. Chinook, coho, 4.6 miles of the estuary are located within the city chum and steelhead are common; pink, sockeye, of Seattle. sea-run cutthroat trout and bull trout are rare. The last 5.3 miles of the Duwamish are dredged for Chinook salmon returning to the Green River navigation and contain deep water habitats where have been a mixture of natural and hatchery none previously existed (Warner and Fritz, 1995). Chinook salmon since approximately 1904, when This lower area has been developed for water the first hatchery fish returned to the Green River dependent commerce and heavy industry. The Hatchery on Soos Creek. The naturally spawning Port of Seattle operates a series of terminal facilities component of the Green River Chinook run at the mouth of the river. contains a mixture of wild and hatchery Chinook. Approximately 3-12 million Chinook salmon have The tides in the Duwamish River estuary have been released into the Green River each year since marked inequalities in the successive high- or low- 1953. water stages. The datum plane (0 point) for tide height in the Duwamish River estuary is mean There has been no means to differentiate hatchery lower low water at a tide reference station about 1 Chinook from natural Chinook salmon in the past. mile northeast of the estuary mouth. According to Draft run-re-construction information for the years the Army Corps of Engineers, the mean tide stage 1989 – 1997 inclusive indicates approximately 56 is 6.5 ft above MLLW, and maximum and mini- percent (range: 25 to 83 percent) of the natural mum estimated stages are 15.00 ft ± 0.5 ft above escapement in the mainstem Green River are from MLLW and 4.5 ft ± 0.5 ft below MLLW, respec- hatchery reared and released fish (Cropp, pers. tively (KCDNR, 2001). comm. 1999 reported in Kerwin et al. 2000). It is not possible to determine to what extent the Circulation of water within a stratified estuary remaining approximate 40 percent of the mainstem comprises a net upstream movement of water Green River escapement has its ancestry from within a lowermost salt-water wedge and a net hatchery origin fish that have spawned for one or downstream movement of fresher water in the more generations in the wild. layer overriding the wedge (Pritchard 1955). The saline wedge water, which has its source in Elliott In the spring of 2000, 100% of the hatchery Bay, oscillates upstream and downstream with the Chinook were marked with an adipose fin clip

59 Seattle’s Aquatic Environments: Duwamish Estuary have resulted in existinghabitatconditions that Extensive waterregimeand channelmodifications Physical Changes Historical Modifications KCDNR, 2001). (T. Cropp,personalcommunicationreportedin than anyotherhatcherystockinPugetSound hatchery displayahighermarinesurvivalrate Chinook salmonreleasedfromtheGreenRiver 1997) (KCDNR,2001).WDFWreportsthat last 30yearsandin7ofthe10(1988to Escapement goalshavebeenreachedin12ofthe WDFW is5,800(WDFWandWWTIT1994). in 1989.Theescapementgoalsetforthisstockby and themaximumescapementof11,512occurring minimum escapementof1,804occurringin1982 escapement forthepast20yearsis6,153,with based onrecentescapementlevels.Theaverage status oftheGreen/Duwamishstockishealthy and Wildlife(WDFWWWTIT1994),the According totheWashingtonDepartmentofFish KCDNR, 2000). basin (WDFWunpublisheddatareportedin stocks isnotevidentintheGreen/Duwamish downward trendcommontootherPugetSound earlier years(1968to1982),indicatingthatthe during recentyears(1983to1998)compared averaged 20,900fish.Runsizetendedtobehigher ranged from12,750in1982to40,5081989and Chinook salmonintheGreen/DuwamishRiver From 1968to1998theestimatedrunoffall (0.87%)(Weitkamp to ChinookreleasedfromtheIssaquahhatchery Snohomish (0.45%),andSkagit(0.23%),butsimilar Nisqually (0.45%),HoodCanal(0.51%), 0.76%) tendedtobesomewhathigherthanthatof survival ofGreenRiverfallChinooksalmon(avg. in survivalwasfoundbetweensystems.However, for allstocksinyears.Nostatisticaldifference 1972-1993, butannualestimateswerenotavailable time periodofanalysisencompassedbroodyears Canal) usingCWTreleasesandrecoveries.The (Nisqually, Sammamish,Snohomish,Skagit,Hood several otherwatershedsinPugetSound compared tosurvivalestimatesofChinookin (coded wiretag(CWT)-basedestimates)was Survival ofGreenRiverhatcheryChinooksalmon fish inthefuture.(Weitkamp which willmakeitpossibletoidentifyhatchery et al. 2000). et al. 2000). 60 dam limitsflowstoamaximumof12,000cfs, flood controlandlowflowaugmentation.The the EagleGorgeofupperGreenRiverfor Hansen Dam(HHD)wasbuiltbytheACOEin mum withdrawalof113cfs.In1962,theHoward diversion damontheGreenRiver,withamaxi- By 1913,thecityofTacomacompletedawater percent and81percent. (ACOE), 1997),atotalreductionbetween32 mately 1,700cfs(U.S.ArmyCorpsofEngineers Duwamish Riverwasestimatedtobeapproxi- 1996). By1996themeanannualflowof cfs priortothediversion(Fuerstenberg, Duwamish Riverwasestimatedat2,500to9,000 and Fritz1995).Themeanannualflowforthe about onequarterofitsoriginalextent(Warner Currently theGreen/DuwamishRiverdrains that theGreennolongerreceivedthoseflows. from theBlackRiverintoLakeWashington,so At thissametimetheCedarRiverwasdiverted Locks andLakeWashingtonShipCanalin1916. Salmon BayaftertheconstructionofBallard Washington weredivertedwesttoLakeUnionand made thisdiversionpermanent.FlowsfromLake by afloodin1906,andlaterman-madestructures White RiverweredivertedtothePuyallup present sizeandconfiguration.Flowsfromthe early 1900’sreducedthedrainagebasintoits natural andman-mademodificationsduringthe the WhiteRiver(nowpartofWRIA10).Both Lake Washingtondrainagebasin(WRIA8),and present GreenRiverwatershed(WRIA9),the much largerwatershedincludingallflowsfromthe Prior tothe1910’s,DuwamishRiverdraineda Duwamish Riversystem(Blomberg were nothistoricallypresentintheGreen/ A morenatural Duwamishbeach. et al. et al. 1988). Seattle’s Aquatic Environments: Duwamish Estuary further reducing hydrologic channel forming remain or have been recreated (Weitkamp et al. (KCDNR, 2001). 2000). Since estuarine prey production is most abundant at about +2 to –2 ft. MLLW (mean Most of the major landscape forming events lower low water), this habitat is important to effecting the estuary occurred in the early 1900’s. young salmon (Weitkamp et al. 2000). Also, young During this time, a substantial quantity of filling Chinook commonly feed within about 0.3 – 1 m of and dredging occurred to construct Harbor Island, the water surface. Given the tidal fluctuations in the East and West Waterways, and the Duwamish the estuary, substrate at these middle and lower shipping channel upstream to the Turning Basin. intertidal elevations provide the estuarine shoreline Dredging has resulted in the replacement of 9.3 habitat and water depths most frequently used by miles of estuarine channel habitat with the 5.3 juvenile Chinook salmon (Weitkamp et al. 2000). miles of deep channel habitat that exists today (Blomberg et al. 1988). Filling to increase the Recent habitat management policies and restora- developable land base has resulted in a reduction of tion projects, as well implementation of require- between 96 percent and 99 percent of the inter- ments for mitigation for any new losses of habitat, tidal mudflats and estuarine wetlands historically have begun to address the degraded conditions present in the Duwamish estuary (KCDNR, 2001). along the Duwamish River (Kerwin et al. 2000). Kellogg Island was formed by extensive fill place- The Kellogg Island area has recently been the focus ments, but includes remnants of two historical of efforts to recreate estuarine wetlands and restore channels and has a densely vegetated riparian zone intertidal habitat (Weitkamp et al. 2000). Other and intertidal wetlands. These represent a majority restoration efforts have included a 1.6-acre estua- of the remaining intertidal wetlands in the rine wetland restoration project at the Turning Duwamish Estuary (Simenstad et al. 1991). Basin, Hamm Creek and Seaboard restorations under the Elliott Bay Duwamish River Panel Shoreline armoring in remaining areas has reduced (natural resource trustees administering a settle- the functionality of most of the rest of the inter- ment agreement for natural resources damages tidal habitat. Upper and middle intertidal habitat with Seattle and King County) and various shore- in the estuary has been eliminated by the construc- line improvement projects associated with tion of bulkheads and piers. Upstream of the improvements at the Port of Seattle facilities. Turning Basin, there has been less modification by Although small by historical standards, these shoreline armoring and the construction of piers actions have served to improve habitat conditions and bulkheads and higher quality middle and lower in the estuary. intertidal areas are still found, but extensive diking has reduced the quantity of upper intertidal Tides, Salinity and Sediment Deposition habitats (Weitkamp et al. 2000). Regular dredging operations (every 2-3 years) in Where shorelines are not intensively developed, the Duwamish Waterway have deepened the main substantial middle and upper tidal flat habitat active channel for navigation purposes. A report issued by ACOE (U.S. ACOE, 1997 p.36) implied that due to dredging practices, the tide migrates farther upstream than it had prior to channeliza- tion and dredging. This assumption appears to be valid when considering the combined effects of deepening the channel, reducing the watershed area by 70 percent, and reducing the freshwater dis- charge by 70 percent (U.S.ACOE 1997). Reducing the mean annual flow from 2500 cfs (conserva- tively) to 1700 cfs compromises the stream flow’s ability to resist upstream migration of the tide for longer periods of time than occurred historically. Dredging the channel lowers the elevation of the channel bottom thereby making it more accessible Some places still have mud flats at low tide. Other places have to a wider range of tides (KCDNR, 2001). There- steep rip-rap with no mud flats. fore it is likely that the point of greatest aggrega- 61 Seattle’s Aquatic Environments: Duwamish Estuary tip ofHarbor IslandtotheTurningBasin was 2002, theportionofDuwamish fromthesouth Harbor CleanupandRedevelopment Project.In regulatory reviewsinimplementing theSouthwest the ArmyCorpsofEngineers tocoordinateother 1990’s withtheDepartment ofEcology,EPA,and the PortofSeattlehasbeenworkingsinceearly have beenongoingforovertenyears.Inaddition, sediments andcleanupactivitieswithinthissite Remedial investigationsofuplandsoilsandmarine Compensation, andLiabilityAct(CERCLA). to theComprehensiveEnvironmentalResponse, Environmental ProtectionAgency(EPA)pursuant waters weredesignatedasaSuperfundsitebythe Earlier, portionsofHarborIslandandsurrounding ing methods. will requirefurtherstudyusingbiologicalscreen- standards serveasabasisforidentifyingareasthat 30 toxiccompoundsand8metals.Thesediment and sedimentstandardsareexceededformorethan Initial characterizationsindicatestatewaterquality River andElliottBayareonthestate’s303(d)list. Pursuant totheCleanWaterAct,Duwamish Duwamish. contamination remainsinthesedimentsof occurred havebeeneliminated,buttheresultant Most industrialdischargeswhichhistorically significant impactsonsedimentandwaterquality. industrialization oftheDuwamishEstuaryhashad The urbanizationofthelowerGreenRiverand Quality Sediment ContaminationandWater versus tidalactivity(KCDNR,2001). tion isdistributedastheresultofriverineprocesses by GeoSeaConsulting(1994)ishowmuddeposi- What remainsinconclusiveinthestudycompleted favoring thedepositionofmud(siltsandclays). moval (fromdredgingactivities)mayresultin River isbecomingincreasinglyrare,anditsre- ing (1994)suggeststhatsandintheDuwamish Sediment samplingperformedbyGeoSeaConsult- composition ofthestreambed(KCDNR,2001). previously had,thenitcouldhavechangedthe activity isoccurringfartherupstreamthanit the kindsofsedimentthataredeposited.Iftidal Consulting 1994)andasaresultitmayalsocontrol deposition intheDuwamishWaterway(GeoSea Tidal activityisreportedtodominatesediment moved upstreamfromearliertimes. tion forsaltwateracclimationChinookhas 62 species insamples collectedinPugetSound. species conductedin1998found 39non-native estuary. However,astudy ofPugetSoundmarine habitats orChinooksalmon intheDuwamish impact ofexoticplantand animal specieson There islimitedinformation regardingtheeffector Exotic PlantsandAnimals sp. and levels ofcontaminantsinsalmonprey( Duwamish Estuary.Evaluationofspecifictoxic smolt fromconsumingamphipodsinthe chemicals inthewater,andnoriskstosalmon no riskstojuvenilesalmonfromdirectexposure aquatic lifefromchemicalsinthewatercolumn, Bay. Thisassessmentidentifiedminimalrisksto CSO impactsintheDuwamishRiverandElliott recently conductedawaterqualityassessmentof al. at themajorcombinedseweroutfalls(Weitkamp The largestcurrentdischargesofstormwateroccur industrial dischargesandsedimentcontamination. drains, combinedseweroutfalls(CSOs)and discharges frompublicandprivatestormwater Elliott Bayispotentiallyadverselyaffectedby Water qualityintheDuwamishRiverand actions. conducting studiestosupportnecessarycleanup the PortofSeattleandBoeingCompanyare named totheSuperfundlist.Seattle,KingCounty, 1980s (WarnerandFritz1995). plant wasdivertedfromtheDuwamishin effluent fromtheRentonwastewatertreatment previously reported,presumablybecausethe dissolved oxygenlevelsaresomewhathigherthan summer period.A1994studyreportedthat degrees C)inthelowerriverduringlate temperature canbeexceptionallywarm(22-25 of riparianvegetation(Kerwin increased runofffromimpervioussurfacesandloss to urbanizationanddevelopment,including region overthepast20years,probablyattributable tributaries intheurbanandurbanizingareasof increasing surfacewatertemperaturesinmost the Duwamish.Therehasbeenatrendtowards have beennotedasproblemsintheupperpartof Both temperatureandlowdissolvedoxygen(DO) and transportmodel(KingCounty1999). removed fromthesystemusingasophisticatedfate contributions ofCSOsweremathematically These estimatesofriskdidnotchangewhenthe strate anyrisktothegrowthofyoungsalmon. 2000).KingCounty(King1999) Eogammarus confervicolus et al. ) didnotdemon- 2000).Water Corophium et Seattle’s Aquatic Environments: Duwamish Estuary

Eleven non-native species found in the survey were Green/Duwamish River Chinook historically new observations for Puget Sound. (KCDNR, resulted in both artificially high counts of natural 2001) Phragmites is known to invade and overtake production, resulting from straying hatchery fish, native vegetation in some sites. and the establishment of harvests limits that did not allow adequate wild stock escapement (Myers Overwater Structures et al. 1998). In addition, hatchery management From the Turning Basin (RM 5.3) to the mouth of practices are thought to have led to earlier run- the Duwamish River, overwater structures occupy timing of returning adult Chinook in recent about 12,150 linear feet, or 2.3 miles, on both decades (Weitkamp et al. 2000). banks of the river. This represents about 15 Chinook spawning occurs primarily in the Green percent of the lower estuarine shoreline. River between river mile (RM) 24 and RM 61. Overwater structures in the upper Duwamish Spawning also occurs in larger tributaries including Estuary between RM 11 and RM 5.3 are limited to Soos Creek, Newaukum Creek, and Burns Creek road and railway bridges (KCDNR, 2001). (Grette and Salo, 1986). All these streams join the river upstream of the estuary. No Chinook Chinook Utilization of the Duwamish spawning is known to occur in the estuary or in Estuary smaller streams flowing into the estuary (Weitkamp et al. 2000). The Duwamish estuary provides habitat for: Adult Chinook salmon hold in the lower river o Adult migration (Duwamish to Kent area) until approximately o Juvenile migration and rearing mid-September, depending on temperature and flow (T. Cropp, Green River salmon biologist, o Transition zone for both adults and juveniles WDFW, pers. comm. reported in Weitkamp et al. 2000). Low oxygen levels in the lower river and Adults estuary (e.g., near 14th Ave. bridge) also may The Green/Duwamish River system historically inhibit upstream migration (Miller and Stauffer supported both spring run and summer/fall run 1967, Salo 1969). More recent studies suggest that Chinook salmon. Presently, only summer/fall run the problems of low DO may be somewhat Chinook are thought to exist as a self-sustaining alleviated by changes in the outfall from the population, although spring Chinook are occasion- Renton Sewage Treatment Plant. (Warner and ally found in the system. Green/Duwamish River Fritz 1995). fall Chinook salmon migrate through the Duwamish Estuary from late June through mid- Juveniles November, peaking between late September and Wild Chinook salmon produced in the Green/ late October (Grette and Salo 1986). Duwamish River system are classified as “ocean Three stocks of Chinook are present in the basin— type” fish because they typically spend little time a hatchery stock that is descended from a wild run; rearing in freshwater after emerging from spawn- the Green/Duwamish stock, which spawns ing gravels. Juveniles are found to be abundant in throughout the basin; and the Newaukum Creek the main stem of the Green River mid-February stock, which spawns in this middle tributary of the through April. Green River. The Green/Duwamish and Although juvenile Chinook salmon are present in Newaukum Creek stocks are considered “natural the Duwamish Estuary over an 8-month period, stocks,” defined as naturally spawning fish that are catch data show an abrupt increase in smolts in descended from both wild and hatchery fish mid-May followed by an equally abrupt decrease. (WDFW and WWTIT 1994). This indicates that most of the fish represented in Chinook salmon in the Green/Duwamish River the pulse of abundance were not in the estuary for system are a mix of hatchery-reared fish, naturally more than 2 weeks (Warner and Fritz 1995). producing fish of hatchery origin, and wild Chi- Mark-and-recapture studies conducted by nook. Hatchery strays are thought to have had a Weitkamp and Schadt (1982) showed similar results large influence on wild Chinook stocks in the with most Chinook remaining in the waterway for river. Hatchery-based fisheries management of about two weeks. The longest individual residence 63 Seattle’s Aquatic Environments: Duwamish Estuary Chinook salmon intheupperestuaryat RM 7.5. study alsofoundthehighest densitiesofjuvenile comparison tositeswithother substrates.This habitats, suggestingahigher productivityin ous benthiccrustaceansand smallshrimpatmud strates. Additionally,thisstudy collectednumer- ratios ofsiteswithsand,gravel,orcobblesub- beaches, andthesesitesproduceddoublethecatch greatest catchovershallow,sloping,softmud waterway. WarnerandFritz(1995)foundthe limited amountofnaturalhabitatremaininginthe the DuwamishEstuarymaybeassociatedwith The distributionofjuvenileChinooksalmonin to thesalinitygradientandavailabilityoffood. tion ofjuvenilesintheestuarymayberelatedboth must makeastheyentersaltwater.Thedistribu- habitat forthetransitionalchangesjuveniles One importantfunctionofanestuaryistoprovide Transition toSaltwater to spawninggrounds. habitat foradultsalmonwaitingtoascendtheriver salmon andalsoprovidestransitionholding necessary forthesurvivalofjuvenileChinook The estuaryprovidescriticalhabitatelements Habitat Requirements are morevulnerabletopredatorsduringlowflows. 1971), presumablybecausedownstreammigrants decreased significantlywithlowerflow(Wetherall 1969). SurvivalofmarkedhatcheryChinook nook salmonin1967(1,500cfs)was51-68%(Salo Estimated downstreamsurvivalofmarkedChi- 2000). Chinook juvenilesinthebasin(Weitkamp releases andlittledataisknownspecifictowild thought tobelargelyinfluencedbyhatchery production inthebasin,thesetimingestimatesare on KetaCreek.Giventhehighdegreeofhatchery ery andtheMuckleshootIndianTribe’shatchery ery-reared fishfromtheState’sSoosCreekhatch- curred shortlyfollowingknownreleasesofhatch- Chinook salmonintheDuwamishestuaryoc- Warner andFritz(1995)reportedthatpeakuseof in MayandJune(Meyer Peak abundanceintheDuwamishestuaryoccurs weeks intheDuwamishEstuary(KCDNR,2001). spent 2weeks,andtworecapturedfish6 nook spentatleast1weekintheestuary,half ducted byBostick(1955)indicatedthatallChi- was 24days.Mark-and-recapturestudiescon- et al. 1980;Salo,1969). et al. 64 Food such asinvertebrates andlarvalfish(KCDNR, primary productionandas sourcesofpreyitems These habitatsarevaluable bothasthebasisfor production andavailability forjuvenileChinook. thought tocontributesignificantly tothefood Estuarine saltmarshesand associated wetlandsare of theestuaryislimiting(Weitkamp evidence toindicatewhethertherearingcapacity estuary forprolongedperiods.Thereisnocurrent portion ofjuvenilesthattendtoremaininthe tidal habitatsmayreducethesurvivalofthat intertidal habitats.However,lossofupperinter- oped shorelinescontainavailablemiddleandlower estuary, eventhoseareasadjacenttohighlydevel- habitats; however,approximately63percentofthe primary causeofthelossupperintertidal juvenile Chinook.Shorelinedevelopmentisa mud) areimportantfoodproductionareasfor gradual slopesandsmallersubstrates(cobbleto It isthoughtthatshallow,intertidalhabitatswith were consumedmoreduringtheday. night thanduringthedayandchironomidflies larly (1981) foundthatgammeridamphipods,particu- 1990). Inexaminingdieldifferences,Meyer larval fish,mysids,andcumaceans(Parametrix, includes gammaridamphapods,copepods,insects, the watercolumnofDuwamishEstuary.Prey that occurredinlowerintertidalsedimentsor (1997) foundthatjuvenileChinookfedontaxa feeders inestuaries(Healey1991).Cordell Chinook juvenilesappeartobeopportunistic Basin (WarnerandFritz1995).Meyer ties increasedtonearthosefoundattheTurning at KelloggIsland(RM1.6).Atthisstation,densi- with theexceptionofmost-downstreamstation were observeddownstreamoftheTurningBasin, Steady decreasesinjuvenileChinookdensities mudflats withsomemarshvegetation. natural shorelinescharacterizedbyintertidal 7.5 (WarnerandFritz1995).Theseareasarealso Turning Basin(RM5.2),justdownstreamofRM 1991). Modestdensitieswereobservedatthe intertidal flatsandemergentvegetation(Tanner This areaisarelativelylargenaturalshorelinewith 2001). move offshorewithincreasingsize.(KCDNR, tended tomoveinshoreatnightand ated withbothnearshoreandoffshoreareas,but found thatjuvenileChinooksalmonwereassoci- Corophium salmonis , wereconsumedmoreat et al. et al. 2000). et al. 1981 et al. Seattle’s Aquatic Environments: Duwamish Estuary

2001). Although there has been a loss of between structures and piers, fish predators are rarely 95 and 99 percent of estuarine habitat in the lower present under these piers (Weitkamp and Farley, Duwamish basin, there is no evidence of inad- 1976; Weitkamp and Katz, 1976; Weitkamp, 1982; equate food supplies for existing populations Ratte, 1985; Williams and Weitkamp, 1991). There (Weitkamp et al. 2000). Individual Chinook spend is presently insufficient information to determine relatively limited time in the estuary. Although what effect other predators may have on Chinook limited time is spent in the estuary, Chinook juvenile survival in the estuary (Weitkamp et al. salmon grow significantly during estuarine resi- 2000). dency (Shepard, 1981; Salo 1969). Salo (1969) found that Chinook captured in early June in the Water Quality estuary averaged 76 mm in length while Chinook While sediment contamination and occasional captured in early July averaged 90 mm. In a study water quality deficiencies are commonplace in the of coded wire tagged Chinook fry, Warner and estuary, it is less clear what effects, if any, these Fritz (1995) found that hatchery Chinook in- have on juvenile salmon survival. King County creased their body weight an average of 70 percent found that there were no acute risks to juvenile during the period between release and recapture in salmon from contamination in the water column the estuary. This same study found that juvenile during their recent CSO study (KCDNR, 1999). Chinook spent on average only 25 days rearing in This conclusion was largely attributed to low the mainstem of the river before entering the residence times for water column pollutants and estuary (range 8 to 61 days). the relatively short time juvenile Chinook spend in It should be noted; however, that hatchery man- the estuary. Both factors tend to reduce Chinook agement practices may account for some of the exposure to potentially harmful contaminants. differences between wild and hatchery fish It is thought that historic contaminants in the (Weitkamp et al. 2000). Hatchery Chinook sediments of the Duwamish estuary have little released in the system have historically been reared potential to have a direct impact on juvenile to larger sizes prior to release as compared to their salmon (Weitkamp et al. 2000); however, some wild counterparts. Up until recently, there has investigators have indicated that many of the been no way to distinguish between large hatchery contaminants common in the sediments of the reared fish entering the estuary and wild or natu- Duwamish estuary may have a long-term chronic rally produced Chinook juveniles that have spent effect on Chinook (McCain, et al. 1990; Varanasi et weeks rearing in the natural environments al. 1993; Stein et al. 1995; Arkoosh et al. 1998). (Weitkamp et al. 2000). Additional investigation is necessary to better understand the potential long term effects of water Predator Avoidance and sediment contamination on Chinook survival. Most of the fish predators, such as smallmouth and In addition, the rate and role of natural attenuation largemouth bass, that are found in freshwater is not well understood in the estuary. Given recent systems such as Lake Washington are not present reductions in contaminant inputs, it is not clear in the Duwamish estuary. Predators on juvenile whether, or to what degree, natural burial and Chinook in the Duwamish Estuary are thought to attenuation is reducing contaminant concentra- include river lamprey, juvenile coho salmon, and tions over time (KCDNR 2001). avian species including great blue heron, western While the effect of impaired water quality on grebe, merganser, cormorant, pigeon guillemont, juvenile survival appears limited, the combination and kingfisher. River lamprey may be a significant of low summer flows, low dissolved oxygen levels, predator on juvenile Chinook with 7% of juve- and high temperatures have been shown to delay niles observed showing lamprey marks (Salo, adult migration and increase the time adult Chi- 1969). Specific studies of river lamprey predation nook spend holding in the estuary and lower river on juvenile Chinook have not been conducted in (Miller and Stauffer 1967; Salo 1969; Weitkamp et the Duwamish estuary, but Beamish and Neville al. 2000). The water quality conditions leading to (1995) estimated that lamprey were killing 25% - delays of adult migration are thought to be most 65% of the young Chinook and coho migrating out significant above the South Park Bridge, beyond of the Fraser River. the Seattle city limits, where water quality is Although the estuary contains many overwater influenced more by inflows from the upper basin

65 Seattle’s Aquatic Environments: Duwamish Estuary affected bythesestructures(Weitkamp outmigration throughtheDuwamishestuaryisnot However, manyauthorshavefoundthatjuvenile (Simenstad also increasetheirsusceptibilitytopredation behavior inresponsetooverwaterstructuresmay 1982.). Themodificationofsalmonidsmigrating Tanner 1991;Simenstad nearshore inshallowwater(Weitkamp1982; vulnerable becausetheymigratealongthe Duwamish Estuary,arebelievedtobeparticularly salmon, thetwomostabundantjuvenilesin Ocean. Juvenileocean-typeChinookandchum Sound duringtheiremigrationtothePacific migrating alongshallow-waterhabitatsofPuget tial barriersorinhibitorstojuvenilesalmon Docks andotheroverwaterstructuresposepoten- discussed aboverelatedtowaterquality. Chinook migrationthroughtheestuaryexceptas There arenootherknownbarrierstoadult Habitat Access conditions intheestuary(Weitkamp mid 1990’smaybeimprovingwaterquality provide highersummerflowsimplementedinthe operational changesinHowardHansenDamto wastewater treatmentplantinthe1980’sand that thediversionofdischargesfromRenton Sound (Weitkamp and islessbenefitedbymixingofwaterfromPuget Chinook areseenalongshorelinesthanunder the lowerDuwamish.Theynotedthatmore salmon alongopenshorelinesandunderpiersin Weitkamp andFarley(1976)observedjuvenile This recreatedoff-channel habitatprovidesshallow waterrefugeathightide. et al. 1982). et al. 2000).Itshouldbenoted et al. 1991;Simenstad et al. et al. 2000). 2000). et al. 66 by moderatetohighriverflowsintothelower derived fromtheupperwatershedistransported tions ofseveralkeyprocesses(Figure6).Sediment estuaries anddeltasareformedbycomplexinterac- Off-channel habitatsinlowerriverareasincluding areas forjuvenileChinook. channel habitatareasarealsoimportantforaging river, andfrompredators.Themarginoff currents presentwithinthelowersectionsof outmigration periodofChinook,fromtidal currents whichmaybehighduringthespring channel habitatsproviderefugeareasfromriver off channelhabitatareas.Channelmarginand habitats alongthemarginsofriverbank,and in largerriverssuchastheDuwamishareshallow preferred habitattypeforjuvenileChinooksalmon juvenile Chinooksalmononahistoricalbasis.The provided themostimportanthabitatareasto channels, sloughs,andotheroff-channelhabitats within thisareaisnotwellunderstood.Side although thelengthofresidencybythisspecies as arearingareabyjuvenileChinooksalmon, drainage intoPugetSound.TheDuwamishisused juvenile ChinookmigratingoutoftheGreenRiver important habitatandphysiologicalfunctionsto The DuwamishRiverandestuaryprovideseveral Landscape andHabitatFormingProcesses the Duwamish tures actuallyimpedejuvenilesalmonmigrationin clarify ifbehavioralresponsestooverwaterstruc- (KCDNR 2001).Furtherinvestigationmayhelp enter areascoveredbypiersandoverdeeperwater piers, butthatcohoshowedlittlereluctanceto . rivers, afinely estuary areasof the deltaand side channels.In such asoxbowsand channel habitats time toformoff- lateral basisover meanders ona highly sinuous,and depositional areasis these lowgradient river channelin floodplain. The to formabroad natural conditions deposited under river, whereitis Seattle’s Aquatic Environments: Duwamish Estuary outbranching network of channels called “distribu- filled for industrial and residential development. taries” is typically formed by the interaction of Dikes and levees which have been constructed along river currents and tidal processes. These habitats sections of the Duwamish for flood protection are scarce under current conditions as a result of further hinder the formation of off-channel habitat extensive channelization and dredging of the areas by restricting the active floodplain to a narrow Duwamish River channel, and industrial develop- corridor along the mainstem river channel. Tide ment along the Duwamish shoreline. gates intended to prevent saltwater intrusion into urban areas also prevent the tidal currents from Almost all of the off-channel habitats that were forming and maintaining blind sloughs and other historically present in the lower Duwamish River off-channel habitat areas. Extensive armoring (e.g., and estuary were destroyed during the late 1800s riprap) and bulkheading along the banks of the and early 1900s when the lower Duwamish River Duwamish now inhibit the lateral migration of the was channelized (straightened and deepened) to river, preventing the formation side-channels, create a navigation channel, and when natural oxbows, and sloughs. channel meanders, sloughs, and side channels were

Duwamish River Diagram Urban Landscape Habitat Habitat Population Constraints Processes Processes Requirements Functions

Land Sediment Inputs Development Channel Hydrology Formation/ Shallow and Complex Habitat Upstream Water (flow regime) Maintenance Juvenile Storage & Predator Survival Diversions Tide Magnitude& Littoral Avoidance Periodicity Vegetation Channel Modifications Food Juvenile Organic Matter Woody Debris Growth and Transport Accumulations Bulkheading Brackish Condition and Armoring Nutrient Salinity Gradient Water Cycling Juvenile Overwater Benthic Smoltification Structures Production Riparian Adult Tributary Vegetation Zooplankton Migration Modifications Production Heat Flux & Transport Non-point Water Quality Contaminants

Barriers Habitat Access

Figure 6. Hierarchical relationship between urban constraints, landscape processes, and Chinook habitat requirements in the Duwamish River system.

67 Seattle’s Aquatic Environments: Duwamish Estuary factors forjuvenileChinooksurvivalandfitnessinnearshoreareas. Based ontheanalysisabove,followingtablesummarizesourunderstandingofmostsignificant ucinFnto odto omn rcse Constraints formingprocesses Habitat condition Habitatcharacteristic/ Function Habitat Function Population upmigration Adult saltwater transition to Juvenile outmigration rearing and Juvenile off-channel habitat anduppermiddle intertidalhabitatsemerge askeyareasoffocus. Among thesefactors,the protection andrestorationofestuarinewetlands complex Access Water Brackish Access Quality Water Availability Food Avoidance Predator river andestuary No barriersinmainstem connected tomainchannel distributaries) thatare habitat areas(e.g.,sloughs, Complex off-channel refugia for rearingandhabitat Access tooff-channelareas river andestuary No barriersinmainstem Clean andcoldwater channel habitats along banksandwithinoff- debris, gravels,andcobbles) macrophytes, woody Diverse substrates(esp. through off-channelareas Hydraulic continuity channels) sloughs, anddistributary (including sidechannels, Off-channel habitats small cobbles) Small substrates(mudto tide) depth from-2ftto+6ft Shallow water(1morless Preliminary Focus Areas 68 Flow Regime Tide magnitudeandtiming Hydrology side channels Hydraulic connectivityof Flow regimeoftributaries oxygen demand) and deposition(biological Organic mattertransport watershed Heat transportfromupper dissolved oxygen) warmer water,reduced increase potentialfor Flow Regime(lowflows growth Riparian vegetation algae growth Aquatic macrophyteand zone andsaltwedge) densities withinmixing Salinity change(highfood from upperwatershed Organic mattertransport and deposition Woody debristransport formation) pattern (off-channelhabitat Tidal magnitudeand channel habitatformation) transport sediments;off- Flow regime(highflows watershed, bankerosion) Sediment sources(upper flow periods warm waterduringlow may behinderedby Upstream migration Channelization Upstream dams (including filling) Land development culverts by floodgatesand and tributariesblocked habitat areas Access tosomeoff-channel debate contaminant impactsunder uncertain. Sediment Impacts ofcontaminants last twodecades substantially improvedwithin Water qualityconditionshave inflows Reduction infreshwater CSOs vegetation Loss ofriparian Tributary diversions channel habitats Reduction inside- bulkheading Bank armoringand mixing zone) freshwater -saltwater greatest within Channelization (impacts Upstream dams Loss ofriparianvegetation Overwater structures Filling ofside-channelareas including dredging Channel modifications Dike andlevees bulkheading Bank armoringand Seattle’s Aquatic Environments: Duwamish Estuary

Habitat Improvement Projects in the Duwamish Estuary Habitat improvement projects should focus on improving those habitat qualities that the science indicates will likely provide the greatest benefit for fish. Habitat restoration projects will be monitored whenever possible. Monitoring will track those critical variables that will help the City to assess effectiveness in meeting project objectives. The City will seek to design and monitor habitat restoration projects that create benefits for multiple species where this practical and where doing so does not undermine the main objec- tives of the project. The following table notes projects which have already been completed and projects which might be considered, noting the benefits for fish which each project may create. (Many existing projects in the Duwamish have been done with Port of Seattle participation.) Project Name Project Cost Habitat Requirement or estimate Predator Food Brackish Status of Project Project Description Avoidance Availability Water

1st Ave South Property negotiations are now going Restoration Intertidal Complex Bridge on to close out the 1st Ave. South Bridge of upper and vegetation off-channel project. Shoreline at the northwest side middle habitat areas Potential of the bridge will be converted to an intertidal Bank (e.g., sloughs, intertidal slough similar to Seaboard. habitats revegetation distributaries) This area is adjacent to the outlet that are for the SR-509 wetlands. connected to main channel

2nd Ave S. Street This street end has good middle to lower Restoration end intertidal habitat. Regrading of the bank of upper and will increase the middle and upper middle Potential intertidal areas. intertidal habitats

Ball Foster This non-water dependent business fully Improved Glass Bank uses its parcel with a truck driveway bank Improvement abutting the river. When they repaired conditions their bank armoring, they used smaller Completed rock, and cleaned up rubbish from the intertidal area. Though there is nothing visible that looks like a restoration project, this work was likely beneficial to juvenile salmonids

Boeing Public Boeing did a partial bank set back and Restoration Intertidal Complex Access Bank some revegetation to create a public of upper and vegetation off-channel Revegetation access site on the bank of one of their middle habitat areas buildings. The site needs some intertidal Bank (e.g., sloughs, Completed stewardship and additional restoration habitats. revegetation distributaries) will increase the value of the area for that are Potential salmonid habitat. Some work may be connected to possible in conjunction with sediment main channel remediation expected just up-river from this site. In addition, if the disincentives of the Shoreline Management Act were removed, there is ample area to dramatically increase the middle and upper intertidal habitat.

69 Seattle’s Aquatic Environments: Duwamish Estuary Completed Bank Revegetation Gateway North Potential Duwamish Diagonal Completed Intertidal Habitat Turning Basin Coastal America Potential City LightSouth Potential Station City LightPump Completed Habitat Park Intertidal Cecil B.Moses future toincrease intertidalhabitat. be includedinrestorationdone inthe City LightPumpStationsite andcould river’s foodweb.Itisadjacent tothe contributes detritusandinsects tothe members. Thebankrevegetation developed andkeptupbycommunity Ave. S.andE.MarginalWayhasbeen The streetendat8 aggregation siteforsalmonidjuveniles. part oftheriverseemedtobeamajor the Muckleshootsabout5yearsago,this wedge. Duringbeachseiningdoneby salmonids attheendofsaltwater Together thesesitesareanchorfor river fromSite#1(seelaterinthistable). Panel. Thissiteisdirectlyacrossthe through theElliottBayRestoration been restoredtoanintertidalslough site belongstoKingCountyandhas Also knownasNorthWind’sWeir,this This smallpublicaccessareaoff8 of theElliottBayPanel. remediation isdoneundertheauspices work whentheproposedsediment may beabaseforadditionalhabitat There isasmallcoveattheoutfallthat and removalofaderelictferryboat. line, replantingofintertidalvegetation, removal offill,regradingthebank America grant.Restorationincluded restored withassistancefromaCoastal This PortofSeattlepropertywas salmon. important transitionareaforjuvenile Kenco Marinesiteandwithinan at thissitejustdownriverfromthe There ispotentialtorestoretheshoreline site. existing GatewayNorthpublicaccess access siteaswell—adjacenttothe so thatthesitewillbeagoodpublic slough. Publicamenitieswillbeincluded be developedasanintertidalmarshor Georgetown SteamPlant.Thesitewill station whichdrewwaterforthe riverbank, istheoldCityLightpump future. Justnorthofthissite,onthe some optionsforrestorationinthe th Ave.S.willsupply 70 th habitats intertidal middle of upperand Restoration habitats intertidal middle of upperand Restoration habitats intertidal middle of upperand Restoration habitats intertidal middle of upperand Restoration habitats intertidal middle of upperand Restoration revegetation Bank revegetation Bank vegetation Intertidal revegetation Bank vegetation Intertidal revegetation Bank vegetation Intertidal revegetation Bank vegetation Intertidal main channel connected to that are distributaries) (e.g., sloughs, habitat areas off-channel Complex main channel connected to that are distributaries) (e.g., sloughs, habitat areas off-channel Complex main channel connected to that are distributaries) (e.g., sloughs, habitat areas off-channel Complex Seattle’s Aquatic Environments: Duwamish Estuary

Gateway South This small public access area off 8th Bank Bank Revegetation Ave. S. and Riverside Dr. S. has been revegetation developed and kept up by community Completed members. The bank revegetation contributes detritus and insects to the river’s food web.

Glacier N.W. Bay One of Glacier NW ‘s facilities sits in Intertidal this remnant of a meander. The bay is a vegetation Potential good intertidal mudflat. Glacier is considering doing some bank revegeta- Bank tion to increase the insects available to revegetation aquatic life that use the bay. Glacier NW uses this site to unload Portland cement. It has a cement dock built at the edge of the dredged waterway, so it does not cover the shallow waters of the mudflats. The dock has widely spaced piers and is relatively narrow, so light can get under it. This is a good design for fish as it has less overwater coverage than older wooden docks. The operation of transferring the cement to the silos is done through a closed system.

GSA Coastal The U.S. General Services Restoration Intertidal Complex America Site Administration hosted a Coastal of estuarine vegetation off-channel Intertidal Habitat America project that took out a part upper and habitat areas of the parking lot at the south end of middle Bank (e.g., sloughs, Completed the riverbank and pulled back part of intertidal revegetation distributaries) an old dock. The area was planted habitats that are but otherwise left to develop into an connected to intertidal mudflat. There is significant Restoration main channel erosion happening because of boat wakes of upper and and it may be necessary to do some middle armoring of the bank edge in the near intertidal future. habitats

Hamm Creek This site, belonging to Seattle City Light, Restoration Complex Intertidal Habitat is a restoration done by King County of upper and off-channel under the Elliott Bay Restoration Panel. middle habitat areas Completed Hamm Creek, previously in a pipe, now intertidal (e.g., sloughs, flows into the new intertidal slough. habitats distributaries) that are connected to main channel

Herring’s House The old Seaboard Lumber mill site has Restoration Intertidal Complex Park Intertidal been transformed into an intertidal of upper and vegetation off-channel Habitat marsh of nearly two acres, along with an middle habitat areas extensively planted upland buffer with intertidal Bank (e.g., sloughs, $5,000,000 native trees and shrubs. habitats revegetation distributaries) that are Completed connected to main channel

71 Seattle’s Aquatic Environments: Duwamish Estuary Completed Habitat Basin POS Turning Potential LaFarge T-108 Underway & Revegetation Bank Improvement Kenco Marine Completed Waterway Kelp BedsEast Completed Intertidal Habitat Kellogg Island

Intertidal intertidal vegetation. regrading thebanklineandreplanting intertidal habitatbyremovingfill, Restoration ofmiddleandupper East Waterwaydredgespoils. part ofthemitigationfordisposal intertidal sloughatthispropertyas indicated theywilllikelycreatean public accesssite.ThePorthas Port’s existingT-108restorationand This Portpropertyisadjacenttothe structures. and removingfilldockpier Turning Basinsite,regradingthebank Work willbesimilartothePOS significant workatthesitethisyear restoration planandexpecttodo Indian Tribe.Theyhavedrawnupa Panel andisownedbytheMuckleshoot auspices oftheElliottBayRestoration This sitewaspurchasedunderthe increase aquatichabitat. channel andestablishedkelpbedsto The Portbuiltsomemoundsinthe even bykayak. west channeldrainsandisimpassable other estuarinewildlife.Atlowtidesthe island hostsherons,osprey,otters,and the elevationstointertidalmudflats.The removing someofthespoilstoreduce been doneonthenorthendofisland, dredging spoils.Somerestorationhas mudflats) hasbeentherepositoryfor This island(aremnantoftheoriginal 72 habitats intertidal middle upper and of estuarine Restoration habitats intertidal middle of upperand Restoration habitats intertidal middle of upperand Restoration revegetation Bank vegetation Intertidal revegetation Bank vegetation Intertidal vegetation Aquatic revegetation Bank vegetation Intertidal main channel connected to that are distributaries) (e.g., sloughs, habitat areas off-channel Complex main channel connected to that are distributaries) (e.g., sloughs, habitat areas off-channel Complex Transition Seattle’s Aquatic Environments: Duwamish Estuary

Puget Creek The south end of T-107 is where Puget Restoration Intertidal Complex Estuary Creek would have emptied to the of upper and vegetation off-channel Duwamish if it were still in its natural middle habitat areas Completed channel. Instead, it enters the Duwamish intertidal Bank (e.g., sloughs, through a pipe somewhat downstream. habitats revegetation distributaries) The Army Corps of Engineers created that are this intertidal area in 1999. If Puget connected to Creek is ever daylighted, it will provide main channel a source of freshwater to this off-channel area. Daylighting the Creek is problematic: 1) the geometry of getting the creek under the road and railroad and over the Renton Effluent Transfer pipe while landing on the beach at the right height is challenging. 2) The creek has a high pH likely related to running through remnants of old cement kiln dust deposited upstream. The latter problem reduces the value of the creek for sustaining meaningful habitat for salmonids though the water quality issues are reduced once the creek mixes with Duwamish water.

SeaKing Industrial This site, in unincorporated King Restoration Intertidal Park County, has some good stormwater of upper and vegetation detention ponds. The owner has middle Potential indicated an interest in looking at intertidal Bank potential shoreline restoration designs. habitats revegetation

Site # 1 Intertidal Curtis Tanner identified this site for Restoration Complex Habitat restoration during the concept study of upper and off-channel done for the Elliott Bay Restoration middle habitat areas $1.85 million Panel. In the March 2000 Salmon intertidal (e.g., sloughs, Recovery Funding Board grant round, habitats distributaries) Underway WRIA 9, (the Green/Duwamish that are watershed planning group), was awarded connected to $500,000 toward acquisition of the main channel parcel. The site has been acquired. The real-estate equity will serve as the required match for the Army Corps of Engineers to create an intertidal slough under the Ecosystem Restoration Study, a General Investigation Study done by the Corps in conjunction with the Green /Duwamish Forum in the late 1990s. Seattle contributed $100,000 to this important regional project.

73 Seattle’s Aquatic Environments: Duwamish Estuary Potential T-105 shoreline Completed America Site T-105 Coastal Completed Bench T-104 Intertidal Completed Wetlands SR 509 Underway $350,000 Improvements Bridge Bank Spokane Street Underway Improvements Revival Bank Duwamish South Park rearing areasforfish. the future,thusincreasingcontiguous restoration projectonthisshorelinein pilings. ThePortintendstodoa currently mudflatsandmanyoldwood river frontage,ownedbythePort,thatis Just upriverfromT-105publicaccessis area. shoehorning habitatintoanindustrial spring/summer. Itisagoodexampleof Chinook juvenilesathightideinthe the river,whichhostschumand includes alongchannelperpendicularto This PortofSeattlePublicAccesssite the shorelineinEastWaterway. The Portcreatedanintertidalbenchon River. through atidalsloughtotheDuwamish pond andawetland.Thewetlanddrains WSDOT createdastormwaterdetention During theconstructionofSR-509 boat waketoavoidheavyarmoring. adequately protectedfromerosion site isbehindawingwallandmaybe middle andupperintertidalhabitat.The regrading theshorelinetoincrease conducted afeasibilityanalysisfor shoreline underthebridge.SPU are landscapingthesiteonnorthwest Metro, thePortofSeattle,andSDOT also revegetatethebank. middle andupperintertidalhabitat doing somebankworkthatwillincrease issue. Howeverthereisapossiblityof septic, creatingapotentialwaterquality the SliveronRiver,iscurrently unincorporated KingCounty,knownas concept hasbeendeveloped.Thisareaof largely residentialarea.Aproject riverfront propertyownersinthis create interestinbankrestorationamong Charlie Cunniff,ofECOSS,hashelped 74 habitats intertidal middle of upperand Restoration habitats intertidal middle of upperand Restoration habitats intertidal middle of upperand Restoration habitats intertidal middle upper and of estuarine Restoration habitats intertidal middle of upperand Restoration habitats intertidal middle of upperand Restoration revegetation Bank vegetation Intertidal revegetation Bank vegetation Intertidal revegetation Bank vegetation Intertidal revegetation Bank vegetation Intertidal revegetation Bank revegetation Bank vegetation Intertidal Seattle’s Aquatic Environments: Duwamish Estuary

T-108 Intertidal The Port developed a public access site at Restoration Intertidal Habitat this street end and also pulled back a of upper and vegetation small intertidal slough to the north of middle Completed the public access. This site is adjacent to intertidal Bank the LaFarge site—a potential restoration habitats revegetation site.

Addressing Uncertainties

Biological indicators The Duwamish estuary may be less of a limitation to Chinook salmon in WRIA 9 than is initially indicated by the enormous loss of pre-settlement intertidal habitat and estuarine wetlands. However, due to long standing and intensive hatchery plants in the basin, the specific needs and limiting factors for wild Chinook are poorly understood. In the longer term, a significant body of research is needed to address how, and to what extent, hatcheries and habitat loss have affected wild Chinook in the Green/Duwamish River basin. Pit tagging studies and fin-clipping all hatchery Chinook released in the basin will assist in this regard. Key research and assessment issues include: 1. The identification of specific habitat needs related to wild Chinook through the entire Green/Duwamish River, including the estuary. 2. Quantification of mortality of wild Chinook at each life stage. 3. The role of predation on juvenile Chinook in the estuary. 4. Impact of contaminated sediments on juvenile Chinook survival. 5. Habitat preference in nearshore areas of wild versus hatchery juvenile Chinook. 6. The characterization and distribution of various life-history strategies for wild Chinook in the basin. 7. The effect of overwater structures on juvenile salmonid mortality in the estuary.

75 Seattle’s Aquatic Environments: Duwamish Estuary GeoSea Consulting.1994. Sedimenttransportin Fuerstenburg, R.R.,K.Nelson,andBlomquist. Cordell, J.R.,L.M.Tear,K.Jensen,andH. Cordell, J.R.,L.M.Tear,K.Jensen,andV. Cordell, J.R.,L.M.Tear,C.A.Simenstad,and Blomberg, G.,C.Simenstad,andP.Hickey.1988. Beamish, R.J.,andC.M.Neville.1995.Pacific Arkoosh, M.R.,E.Casillas,P.Huffman, Literature Cited Olympia. of Ecology,ToxicsCleanup Group, Prepared forWashingtonState Department implications toestuarinemanagement. Elliott BayandtheDuwamish River,Seattle: Water Management,Bellevue,Washington. Washington, USA.KingCountySurface to salmoniddiversityintheGreenRiver, 1996. Ecologicalconditionsandlimitations Research Institute,Seattle. University ofWashington,Fisheries results from1997monitoringstudies. America restorationandreferencesites: Higgins. 1998.DuwamishRivercoastal 97-09, Seattle. ies, FisheriesResourceInstitute,FRI-UW- University ofWashington,SchoolFisher- Results from1996monitoringstudies. America restorationandreferencesites: Luiting. 1997.DuwamishRiverCoastal 96-12, Seattle. ies, FisheriesResourceInstitute,FRI-UW- University ofWashington,SchoolFisher- sites: resultsfrom1995monitoringstudies. Coastal Americarestorationandreference W. G.Hood.1996.DuwamishRiver Washington. Sound WaterQualityAuthority,Seattle, Puget SoundResearch.VolumeII. Proceedings oftheFirstAnnualMeetingon over thepast125years.Pages437-454In: Changes inDuwamishRiverestuaryhabitat Fisheries andAquaticSciences.52:644-650. (Lampetra ayresi).CanadianJournalof Fraser Riverplumecausedbyriverlamprey salmon andPacificherringmortalitiesinthe 127:360-374. actions oftheAmericanFisheriesSociety nated estuaryto juvenile Chinooksalmonfromacontami- Varanasi. 1998.Increasedsusceptibilityof Clemons, J.Evered,E.Stein,andU. Vibrio anguillarum . Trans- 76 Meyer, J.A.,T.A.Pearce,andS.B.Patlan.1980. McCain, M.,D.Fuller,L.Decker,andK. King CountyDepartmentofNaturalResources King County.1999.CombinedSewerOverflow Kerwin, John,andTomS.Nelson.December Heg, R.1952.DuwamishRiverChinookstudies. Grette, G.B.andE.O.Salo.1986.Thestatusof report, Olympia,Washington. Fisheries AssistanceOffice, unpublished ington, 1980.U.S.FishandWildlifeService, salmonids intheDuwamishEstuary,Wash- Distribution andfoodhabitsofjuvenile west Region. Agriculture, ForestService,PacificSouth- Currents, Number 1, U.S.Departmentof California. FishHabitatRelationships and inventoryproceduresforNorthern Overton. 1990.Streamhabitatclassification 2001 (ReviewDraft).292p. Resources Seattle,Washington.January King CountyDepartmentofNatural ates, Inc.Seattle,Washington.Preparedfor ates Seattle,Washington,ShapiroAssoci- Washington, StriplinEnvironmentalAssoci- ington, PentecEnviron-mentalSeattle, Marine SciencesLaboratorySequim,Wash- (WRIAs 8and0).PreparedbyBattelle Sound, IncludingVashonandMauryIslands Ecosystem: EasternShoreofCentralPuget (KCDNR). 2001.StateoftheNearshore WA. Department ofNaturalResources.Seattle, by Parametrix,Inc.andKingCounty Duwamish RiverandElliottBay.Prepared Water QualityAssessmentforthe Resources. King CountyDepartmentofNatural ington ConservationCommissionandthe sheds (WRIA9andVashonIsland).”Wash- Duwamish andCentralPugetSoundWater- naissance AssessmentReport,Green/ 2000. “HabitatLimitingFactorsandRecon- Progress Report.July-November1952. Washington DepartmentofFisheries 213 p. Corps ofEngineers,Seattle,Washington. River system.FinalreporttotheUSArmy anadromous fishesoftheGreen/Duwamish Seattle’s Aquatic Environments: Duwamish Estuary

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