DOUGLAS SKIDMORE KENNETH K. CHEW
LOAN COPY ONLY MUSSEL AQUACULTURE
PUGET SOUND
.p . TECHNICAI. REPORT ! r OP@QN4~ I
I;IMKSTII'QI'~ g, I;.;,«0:;n~t~v
MusselAquaculture in PugetSound
DouglasSki6nore and Kenneth K. Cher.
WashingtonSea Grant Program Universityof Washington~ Seattle Preface 1 Growingbrussels 1 Sealro tom ,'ulture SeedCr>llection Derrsities Substrates Cleansing About the Authors Wasllrllgarrd Packillg DouglasSkidmore received a Master ol' Fisheries degree from the Lrruversih rrfWashingtmr School Irroirlems 4 ol'Fisheries. He is nova partnerirr RaceI,agoon Mussels. Kenneth K Chewis professor arrd Pote»tialof Seaho tomCulture rrr Puget Sound chairmanof L!ivisionof Aquacultureand invertebrate Fisheries at the I'niversity rrf Washington Ijouchot arrd intertida! '.ulture 6 School of Fisheries. SeedCollection 6 Chrc~ photo of Race/agoon mrrsre/rAF Roger rcbrerbor TransferrirrgMussel Seed to HigherGrou»d 6 .onstnrctron 6 KeyWords I Mussels 2. Aquaculture Mussels Tides,Temperatures, a»d Salirrities 7 Harvesting I'rohlerns 8 Corrsiderationsof Houchot or intertidalCulture irr Puget Sourrd 8 irrterrirlalCulture Methods I:sed in PugetSound 8 Raft Culture 9 SeedCollection 10 AttachingSeed to Ropes 10 RaftConfigurations 11 Thisresearch and this publication were supported by grant NA84AA-D-I I, projects R?A-16 T}«rrrrrrrg 11 andA PC-S,from the National Oceanic and Atmospheric Administration to the Washington 1!epuration I I SeaGrant Program. Problems 11 Sur'talrilityof RaftCulture for PugetSound 11 RaftCulture in pugetSound 12 Lorrglines I ' Copiesol'this report may he ohtairred from Washi»gto» SeaGrant Commurrications, Collegeof SeedCollectors I 'r Ocearra»d Fishery Sciences, I'niversity of Washington,Seattle, WA 98195 prov,Out I'rohlems I'r Washingto»SeaGrant Program Suitahilityof I.o»glineCulture Ii CollegeofOcean and Fishery Sciences 2 SeedCollection in PugetSound 15 'rr versitlrrf Washington HG-,'r0 Methods I S Seattle,WA 9819! Dtiliai»gNatural Seed Iteds IS CatchrngSeed on CollectorLines 1S WSG8>-< MusselLarvae Settlement i» Puget Sound Ih October1985 .ountingSamples I? $S.00 AreasSampled 17 SeasonalPatterns of Seulernent 17 Fouling 5? SenlementDensities 22 PennCove 52 WhySome Areas are Better Than Others 22 hianchester 5? I,arvalSettlements Prediction Model 24 Burki In! et 53 TemperatureModel 24 I-:ftectsof IntertidalConditioning on Raft-or Longline-grownMussels to ColdStorage Correlationof EyedLarvae to SettledLarvae 24 Survival 53 HatcheryRearing of Aihrr'luseduir's I.arvae 24 ShellLife of Intertidaland Continuously Submerged htussels 53 Settlement 25 Effectsof IntertidalHardening on ShelfI.ife 54 5 Growth,Mortality and Conditionof NyBlms edNBsand Mythslus References 55 californhxNNsin PngetSound 26 Growthand hlortality of,Qytilus eclulis 26 GrowthResults 27 SeawaterAnalysis 27 FactorsAffecting Growth 27 hiortalities 29 ComparitiveGrowth of Mvlilusedulis from Three Seed Sources in PugetSound 31 Results 32 Condition Index 33 ConditronIndex Evaluations 33 Seabeckand Manchesi.er 34 FightStation Study in PugetSound 34 DryWeight Comparisons 35 Factorsthat influence Condition and Tissue Weight 35 Growthand Survival Comparisons of,V>~tilus err le ornianusand iti'yrilus edult's 36 ExpertrnentalSet-up 37 Resuhs 38 CulturePotential ofNy6!us californianus 39 HatcheryExperiments with Nytilus californianus 40 Spavning of theAnimals 40 RearingLarvae 41 Results 41 Settlement 42 BiologicalConsiderations 44 Conclusions 46 4 Additional Considerations 47 Socio-politicalAspects Permits and leases! 47 Predators 48 ScoterI!ucks 48 Starfish 49 Crabs 49 Weather5VIndwaves and Exposure! 49 Pollution 49 Para!>licShellfish Poisoning 50 REFACK
:uiturinaeconomically important marine organismsis hecoruingm<>rc prvvalsnr worldwide.One animal which has experienced vast utilization in marine aquaculture is the mnusse.Mylilus edulis, the bay mussel, is found worldwide and is the predominant species culturedfor humanconsumption, though several other species are used as weH, In thePacific Northwesta new aquaculture industry is emergingthat is producinghigh quality mussels- again tfytilusedrdis is thecommon species used. Theintent of thispaper is to describetypes of musselaquaculture used around the worldand the evolution of musselaquaculture in thePacific Northwest. ln addition,this reportwill presentinformation concerning mussel aquaculture in PugetSound that has been the resultof tenyears of researchby studentsand facuhyof the Schoolof Fisheriesin the CoHegeof Ocean and Fishery Sciences, University of Washington.We hope this publication will be of valueto existingand future musselaquacuhurists in PugetSound. DouglasSkidmore and Kenneth K. ;hew Februaryl 985
2llrrsrel,0quaeritiiirern Pager Sound garourng.Vuueir tore:raft culture of rnussels began in Spainwithin the last 35 years Korringa, 1976!, the first amountsof seedin PugetSound had to beestablished. In addition, the growth rates of mus- musselfarms in theUnited States were established in the early 1970s in Maine Abandoned selsin PugetSound needed to be determinedand compared to other areasof theworld, Farms!and in PugetSound Penn Cove Mussels!. Since that time the production ofmussels Primaryelforts were directed toward finding areas where adequate seed could be caught and on both coastshas increased and severalmore companiesare now in operation. determiningwhether it wasfeasible to produceseed in hatcheries.Growth and mortality rates Salesof culturedand wild harvestmussels in the PacilicNorthwest have steadily wererecorded for manyareas of PugetSound, High mortality rates of I ytr1rrsedNtis in some increasedsince 1974 Figure I!. Increasedsales are a responsetoincreasing demand for areasprompted research on the aquaculturepotential of anothermussel species Mytiigs highquality shellfish inlocal restaurants, Manyof the finest restaurants inthe Pacific North- californianrrs.The results of theseinvestigations are presented inthis report, along with a westcommonly serve mussels asappetizers or as main entrees. The most common way they reviewof thedifferent methods used to growmussels in variousregions of theworld, areprepared is steamedin a wineand herb sauce. Musselfarming has been practiced insome European countries for 700 years, but Popularityofmussels in the Northwest has increased due to the high quality of local only sincethe 1970sin NorthAmerica Mason,1971!. Theprinciple species of musselcul. culturedmussels, Locally grown mussels have been entered in twonational mussel tasting turedhas been,Ifytilrrs edrdis L, thecommon bay or bluemussel. Over the years, techniques contestsand Washington cultured rnussels from Penn Cove have won both competitions to grow musselshave evolved into threebasic forms: seabottom culture, bouchots or interti- QeearrLeader, 1981!. Washington mussels held two of the top three positions in both com- dal culture!, and raft and longlineculture, Methods differ becausethey evolved out of the petitions. necessityto complywith differing environmental conditions between regions. Bottom culture Mostdomestic mussels now sold in the UnitedStates come from a singlemajor East canbe more successfulunder a specificsituation than bouchotsor raftculture and vice versa. Coastproducer, Great Eastern Mussel Farms, Inc. in Tenants Harbor, Maine. Great Eastern Foradditional information, see the following publications: Korringa, 1976; I.utz, 1974 and dredgeswild and cultured mussels from the sea bottom, Once ashore the mussels are taken 1980;]enkins,1979; Myers, 1981; Mason, 1976; I,utz et al., 1977; loosanoff, 1943.! Some of toa processingplant where they are held in large seawater tanks. Processing issimilar to thesetechniques will besummarized and their potentialapplication in PugetSound discussed methodsused in theNetherlands see Techrriqrres to Grorutrtiussets!, Clumps are separated in thischapter, andwashed by machine and sortedby hand on a conveyor. TheUniversity ofWashington began investigating mussel culture in 1973.This coin- Seabottom Culture cidedwith the establishment of the lirst mussel farm in Puget Sound by Peter Jefferds, Wash- Musselfarmers in The Netherlands and Germany have successfully used bottom cul- ingtonSea Grant support enabled the School of Fisheries, University ofWashmgton, toinvesti- turetechniques for 300years to producemillions of kilogramsof musselsto supplytheir own gatethe potential ofmussel aquaculture in Puget Sound. The approach was to determine countryas well as partsof Franceand Belgium I.utz, 1980!. TheNetherlands government wheremussels could survive and grow in PugetSound at a ratewhich could support viable leasesplots of bottomland 00 x 200rueters; 24 acres!in the shallows of theZeeland and commercialventures, Waddenzeeestuaries for a reasonablefee. Seed mussels are placedon the plotsof land and Severalkey parameters had to be addressed in the investigations. Wildseed sources growto marketsize in 20 months,The annual harvest from TheNetherlands has been in havebeen used by ail mussel farms throughout theworld, but the ability tocatch adequate excessof 100,000metric tons of livemussels, although it hasbeen decreasing in recent years, Bottomcuhure of rnusseisis now beingtried on the northeastcoast of the United States.Natural subtidal beds have been harvested for severalyears, but stock enhancement by planingseed may sustain the harvest of musselsin thatarea. 200 Seed Collection H Almostevery year a naturalsettlement of small mussels occurs in certain regions of 100 TheNetherlands. It is this abundantnatural set of seedmussels which makesthis productive industrypossible. Seed beds are controlledby the Ministry and, on the adviceof oificials,are Z 100 openedin the late spring or summer.Seed mussels are removed Irom the public beds by Annualtiraduct growthand an inferior mussel will result, To obtain the proper growth densities, the foHowing measurementsareused when seed is spread Korringa, 1976!: 1. Wheatgrain-sized seed mussels .5-0.75 centimeters! Density:20 metric tons per hectare approximately 18,000 pounds per acre or 0.4 poundsper square foot!. 2. Bean-sizedseed mussels approximately one centimeter! Density:50-35 metric tons per hectare approximately 27,000 pounds per acre or 0.6 poundsper square foot! . Substrates Plotsof landleased to farmersare generally subtidal below low water!. The plots rangefrom two to seven meters below low water. Growing plots are almost never seen above waterand must be worked by boats with special dredges to inaintainthe plots. The bottom is End view probedwith special sticks to reveal the texture of the substrate. Substrate that is too muddy or Figure2. Scheme toosandy isundesirable formaximum growth: an even mixture of mud and sand is optimal. theNetherlands: ! h Cleansing h ower, ! sorler; I rrrrga,1976! Right So Duringharvesting, siltthat is stirred up by the dredge is ingestedbythe mussels and Mossels. retainedbetween its valves. To remedythis problem before processing and inarketing, mus- selsare taken to a cleansingarea of intertidal water with a hardsandy bottom where they are Weather Wavesand curren scan be the deadliest enemy. Mussel plots are gener- leftto eject the grit. This cleansing period about three to eight days also allows seagulls to allylocated in protectedwaters; however, attimes mnter storms and ice are problems to performa freeservice of removingany starfish and dead or dyingmussels during low tide. contend with. FreshwaterAn influx of freshwaterthat causes a substantialdrop in salinitycan Washingand Packing cause mass mortalities of mussels, Afterbeing dredged olfthe cleansing plot, mussels are taken to the processing plant Silt Musselsproduce silt by their own filtering activity, but if thesubstrate is too wherea specialmachine separates, washes, and packs them at a rateof two to four tons per siltythe mussels cannot stay above the surface of themud and may smother, If siltis depos- hour Korringa,1976!, The machine Figure 2!, whichrequires seven men to operate it, has itedunder the mussels they will try to stayabove it, butthey wiH still bevulnerable to erosion sixstations that the mussels proceed through: duringstrong tidal movemenu. Farmers in TheNetherlands sometimes remove the mussels 1. Hopper mussels are introduced tothe hopper by either conveyer belts or grabs andtow a chain-harrowacross their beds to alleviatethis problem, 2. Breaker a rotatingshaft with off-set pairs of blades every several inches. The shaft BarnaclesWhen barnacles are attached to mussels,they are harder to cleanand turnsat approximately 34rpm when the tube is tightly fiHed with mussels and water, fetcha lowerprice at market, 3. Washer a rotatingcylinder constucted of steelrings, placed so that no mussels fall Potentialof SeabottomCulture in PugetSound through,It is angled at 10' so that the mussels How through slowly as they are washed Seabottomcuhure of musselsprobably has the least potential appfication for use in byseawater pumped through perforated tubes. PugetSound. No subtidal beds ofAfytilur eduh's are known to existin PugetSound, but they 4. Blower mussels drop onto a wirenetting that moves over an upward air current areahundant subtidafly along the northeast coast of the United States. Large subtidal mussel whicheliminates empty shelLs, leaves, or seaweedsuch as ftkvz. bedsare found olf thecoasts of Maine,New Hampshire, and Massachusetts. These beds are 5. Sorter mussels drop from the blower to a rubbersorting belt. Four or fivemen stand harvestedwith dredges and millions of poundsof musselsare shipped throughout the United alongsideand pick out undesirable objects. States.These beds are reseeded and managed like mussel beds in TheNetherlands. 6. Weighingapparatus clean mussels are fed into a hopper,which automaticafly weighs Grovvhngmussels subtidafly isan unlikely prospect in PugetSound, primarily because them.They are then bagged by another worker. of predation.Starfish and crabs are abundant and consume any mussels or othershellfish that happentoappear in thesubtidal zone. Evidence ofthis occurred when several ropes with Problems harvest.sized mussels were inadvertently dropped to thebottom of PennCove. When retrieved ShortageofSeed Anaverage ofone out of five years has a failureof seed, severalweeks later, the lines of mussels had been almost entirely consumed bystarfish. Predators Crabsand starfish can consumelarge amounts of mussels. Evidenceof crabseating the mussels could also be detected. Many of theshells were broken, Crrortvntt;I fussels .1!uxseiAquaculture in Puget,thurre rows,the poles are placed about 20 cemimeters apart and contain 125 poles in a row. indicatingdiat crabs had broken them and devoured the meat inside. Any attempt togrow Double-rowedbouchots have bvo 190-polerows, one meter apart, with polesspaced at32- musselssubtidally would require control of predators byfencing orelimination, a seemingly centimeterintervals. Bouchot rows should be spaced 25 meters from one another but are difficult prospectat best. oftenonly 15-20 metersapart Korringa,1976!. Oakpoles are usedalmost exclusively, and theyare generally4- i meterslong and Bouchot and Intertidal Culture 12 20cmitimeters in diameter at thethick end. Poles are placed by drilling a holein themud Mongthe southern coast of France and in partsof the northern coastline ofNor- withan auger on a tractor.The pole is theninserted into the hole 2-3 metersdeep The top mandyand Brittany, mussel cuhure has been conducted onstakes orpoles called houchets. I..Smeters of poleis coveredwith mussels and the lower portion is sometimes wrapped with Bouchotfarming originated in the Ause de l'Aiguillon, on the coast of France, in 123'>,A plasticto deterstarfish. shipwreckedIrishman, Patrick Walton, placed poles with net strung on them in anattempt to Tides,Temperatures, and Salinities catchseabirds for food Mason,1971!. Not many birds were captured, but mussels grew Bouchotsare locatedon the shallow,gentle sloping shelves of thePertuis Breton profuselyonthe poles. Since then this method has changed little. Space for the bouchot poles regionof theAtlantic coast of France.The tidal range varies from five meters during spring areleased by the French State for 25-year periods. France produces over 50,000 metric tons tidesto two metersduring neaptides. Current velocities can reach two to threeknots on of livemussels annualh, and all a're soldfresh, There are over 1,100 kilometers ?00 miles! springebbs, Water temperatures range from about8'C-20'C in the westernmostsection. of rowsof musselpoles along the French coast. Salinitiesvary little and remain in therange of 32-55parts per thousand. Seed Collection Harvesting Seedmussels for bouchotsare collected on bouchotpoles or on rackswith coco- Theharvest season is from May I February I, andall harvestingisdone by tractors fiberlines. Poles are placed in deeperareas than the growing sites. The poles are planted low intertidallyinJanuary April to allow the growth ofhydroids and other highly desirable with specialattachments to scrapeolf themussels. Grading of musselsoccurs aboard a large 'hairy"textured plants and organisms thatattract mussel larvae. The larvae settle in -2.4 m May-bruneand grow rapidly. Figure3 Racktor seedcollec i tlon. A morerecent seed collection method is racksmade to holdcoco-fiber strands olf 35 cm thebottom. Coco-fiber has the correct texture to inducesettlement of mussellarvae earlier thanthe poles. Seed isalso more easily transported onropes than on poles. Racks are made 60 cm ofpoles placed inrows I.S meters apart and spaced in2.4-meter intervals. Coco-Aber islaid thelength ofthe rows over two levels ofcross bars, one 60 centimeters offthe bottom and the oakpoles other95 centimeters Figure 5!. Therows are generally 25 meters long and contain 25 strandsper level. The seed racks are placed relatively lowin the intertidal area compared to the growing areas. TransferringMussel Seed to HigherGround Afterthe seed reaches a sire of approximately 20millimeters, it is harvested from the polesand packed innylon tube netting called "boudins." The netting ends up resembling a sausageandis approximately fivemeters long and ten centimeters thick. In turn, each is wrappedspirally around the pole, leaving space between thewraps, giving ita candycane stripeappearance. Theextra space allows the rnussels room to grow, so thinning may be unnecessary.This process is shownin Figure4, Ropesladened with seed from the rack collectors are transferred inJuly to growing areas.The coco-Aber rope is cutinto sections 2,5 3meters long, and because ofthe high densityofseed on them, only one section isused for each pole. Cut sections arewrapped on barepoles and left to grow. 10cm Construction Figure4. Makingof "boudin"seed saosages, which are wrapped spirally around boochot poles. Mussels wilt Bouchotpoles are placed in rows50 meters long and aligned perpendicular tothe eventuallygrow out of themesh and cover the poles. coastline.A houchot arow of poles! can be either a singlerow or doublerow. In single Nore Aqrurculfurein Pager Sound GroumgAf uveLr boat,where mussels areplaced ona trellistobe scrubbed andwashed, Workers wearthick rangingfrom three feet to minustwo feet MLLW Figure 5!, glovestohand scrub themussels overthe treUis, thenwash them with jets ofwater oseparate Seedmussels placed in this system for growout are procured in twoways, Seed is themand rinse olf any grit. The srnafler onesare separated ouand are eventually placed eithercaught on lines or placedin meshtubing. Seed caught on lines is collected ina similar backin tube netting obe wrapped back on growing poles. fashionas mentioned earlier in thissection and seen in Figure5, One-hundred-foot linesare strungon racks in the early spring to catch the set in May or June. The seed lines incorporate Problems thesame coconut fibre twine that the French use o catchmussel larvae. Coco hb WeatherGales may occur, and sometimes candamage themussel poles, espe- ~coiri ' ! Lsattrac mussellarvae because of its fibroustexture. Larval mussels seek a srnaUniche ciaflythose that have been weakened bythe work ofshipworms. inw ichto hideanrl coir offers such spaces, Seed cofle tedfr ks, il' PredatorsThough starfish areonh' a slightproblem inthe intertidal area, stin- romharvest are placed in meshtubes 100 feet long Figure4!. In bo hcases the seed lines graysmove induring thesummer months andconsume themussels, Thisproblem isso arestretched out into the rows of pipesand placed into position. severethatlarge mesh nets are strung onthe outside ofthe growing area~each year todeter When musseLsreach harvest size, the lines are remove d omt fr h epipesan abuoyis thepredators. attached oone end. At high ide the lines are pulled into a boatand taken to a cleaning ShipwormsThepoles used tobuild the bouchots systemare made ofwood and arge.The mussels are removed from the lines, separated, graded, washed, and bagged, aretherefore susceptible tobecoming honeycombed andweakened byshipworms. Lifeex- pectancyofpoles isfrom 5-6 years. Raft Culture ConsiderationsofSouchot orintertidal Culture inPuget Sound UsingSpain as an example, rafts iniriafly were constructed ofold hulls of fishing Musselsgrownon bouchots inFrance arerenowned fortheir high quality, andfetch vessels,Timbers were used to build a platformradiating horizontally f'rom the hull for hang- a higherpricethan raft grown mussels fromSpain Korringa, 1976!. Because musselsare ng mussellines Lutz, 1980!, Theselines were used to catchmussel seeseed as weweU as grow row grownintertidally withdaily exposure toair, the shelf lifeof the product isenhanced andthe . size.More sophisticated float design construction 'on has as b eenus ed int' h epast musselshavea somewhat differentflavor and texture than those grown onrafts orlonglines, ten years. whichare continuously immersed, Theability ofthe mussel todevelop a tougher sheUand Culturingofmussels isprevalent inthe protected waters of Spain's Rias. Until 1974, remainclosed when out of water isan adaption which increases itsshelf life in the market. Spairiwas the world's largest producer of mussels,with annual sales of 130,000metric tons Intertidalculture using bouchots orother !yes ofintertidal formations couldbe Lutz, 1980!. However,with the additionof 3.000additional rafts theRi initiatedinPuget Sound, butthere areproblems thatmay beencountered ingrowing mussels crowdede anand production ro dropped to 50,000metric tons per year. Mussel production re- intertidallyhere.Unlike some parts ofFrance, where barnacles arenot much ofa problem, maine epresseduntil 1980, when production increased tonearly 100 000 mmetric tons per barnaclesettlements inPuget Sound are substantial, andthose that settle and grow on mus- year FAO.1985!, selsmust beremoved before themussels canbe marketed. Thisisgenerafly doneby hand The use of rafts for growing mussels is now widespread. though the technolo of raft andisvery time consuming. Barnacles onintertidal mussels areespecially difficuftin that they ge dramaticallywiththe development ofcost-elfective floatsand gear. developa harder, thicker shell than dothose onsubtidal mussels, inaddition, thegrowth rate Raftsare now used in theUnited States, Sweden, New Zealand I and man e me o use in Spainare presented here as an example ofmussel usse ccu lt ure using ofmussels grown intertidafly isusually slower than rnussels grown onrafts orlonglines rafts. becauseexposure tothe air at low tide reduces feeding time. IntertidalCulture Methods Used in Puget Sound Onlyone commercial musselfarm inPuget Sound hasbased itsoperation inthe intertidalzone, Race Lagoon Mussels, a company locatedon Saratoga Passage onthe east side ofWhidbey 1sland atRace Lagoon usesan intertidal longline system togrow mussels, This systemismuch like the system usedto grow oysters inGrays Harbor, Washington. Because thesystem islocated ona beachbetween thehigh tide and low tide water level, itcan only be maintainedon tidesthat are low enough to exposeit, Theimertidal longline used atRace Lagoon consists of100-foot linesthat are staked tothe beach andsupported offthe beach with plastic PVC pipe, The pipes are inserted into Figure5. Ir ter Idallongline system Used aiRace Lagoon. thebeach inrows that consist often support pipes spaced approximately ninefeet apart. The rowsareplaced three feet apart and parallel tothe shoreline. Mussels aregrown attide levels i tuxretAquaculture in Pager5ound C;rprring.'lfu~etr Seed Collection meterrope, Ropes are made from esparto grass, old trawl nets, or synthetics most are Mussellarvae settle in abundanceon the rocks of theintergdal zone in Spain,livery syntheticrope!. Seed mussels reach market size sbeH length of 80-100 milHmeters! in yearseed mussels are scraped olf these rocks. providing the Spanish mussel industry with 12-18months, and each eight- to nine-meter rope can yieM 250 pounds 13 kilograms!of 60 70percent of its neededseed Korringa,1976!, During seed collection season small livemarketable mussels Annually, a raft wiH yield 175,000 pounds utilizing 700 ropes Kor- bnalsare used to transportworkers and seed. On an average Hde, several workers can gather ringa, 19'76;Lutz, 1980! . 1,500kHograms ofseed. The farmers either collect the seed themselves orbuy i , whichis RaftConfigurations sometimescheaper than hiring peopleto collectit. Theremaining portion of seedis coflecteddirectly on ropes suspended from rafts, Anaverage-sized raftis about23 meterssquare and is anchoredin atleast I I meters Ropesare hung from rafts from December through January to catchseed during February ofwater atlow tide. Culture lines are approximately ninemeters long, so they never touch the andMarch. In thePacilic hforthwest, mussel seed generally is caughtin lateApril to early bonom.Rahs are made as simple as possible, concrete or steelfloats have been used, and June. evenstyrofoam andfiberglass arebeing tested Lutz, 1980! . In Spain a woodeneucalyptus AttachingSeed to Ropes frameworkoffive-centimeter-square timbersisused tosupport ropes, The timbers areplaced 45centimeters apart and ropes are hung from them Figure 7!. Seedis collectedwhen it is from8-10 miHimeterslong. The seed mussels are then at achedto theropes with a bandage-liketissue made especially for themussel Industry Thinning Figure6!. Thebandage is wrapped around the rope while the mussels are placed in posi- Afterthree or fourmonths, mussels can become overcrowded, which can reduce tion.The mussels attach to therope in a fewdays and the rayon bandage dissolves, growthor causelayers to separa from e the rope and faU off. Before this occurs the ruussels It takesapproximately 6-7minutes for an experienced worker to load a singleeight- arepartiaHy stripped ofl'the lines and the excess iswrapped onto new lines, One rope may sometimesproduce three or four newones, Depuration Tobe sold fresh in Spain or exported toFrance, mussels must be depurated to eliminateanybacteria derived from sewage and other poUutants thatmay accumulate inthe meat.This is accomplished byplacing them in large tanks and circulating purified water throughthem for 48 hours. Large depuration plants have been constructed tomechanize the process, Problems Kydrographicconditio raSalinity inSpain's Riode Arosa isusually high, with a limitedrange of fluctua ion.Once every six to seven years the river that feeds the bay floods andcauses a freshwater lenseto form on the surface. The top 1-1,5 meters ofthe cuhure linesmay die. PredatorsThere islittle predation bys arfishand crabs, More dangerous arethe sparidftsh, which consume mussels bycrushing them. woodenframework, used in Spain;b! steelball floe ion, FoulingOrganisms Ascidians andsponges grow on culture ropes and compete 8 wooden framework;c! styrofoamfloats attached with withthe mussels forspace and food, Barnacles andpolychaete worms also tend to grow on steel"box" hearne and pealed poles ae crass members theropes, usedby Penn Cove Muesefs Inc.!. Suitabilityof RaftCulture for Puget Sound Raftculture ofmussels inPuget Sound has a goodprospect and is presently being usedby growers inseveral locations, aHof whom use or propose touse combinations ofrafts andlonglines. Raftsoffer the utilization ofthree-dimensional spaceinthe water, allow large quantitiesofmussels tobe grown in a relativelysmall amount ofspace, donot restrict the operationtothe beach area, thereby aHowing a wider selection ofsites! and are inexpensive to construct,The quality of rnusselsproduced on raftsis exceHent:the meat is brilliant white and ender, and the flavor ismild and succulen Penn .Cove raft-grown mussels from Whidbey IO 11 MusselAquaculture in PugetSound SeedCollection in Puget5ound elftcientincatching mussel larvae inPuget Sound, This study used rubberized curled-packing facility.The study sites were chosen to representa widearray of marineenvironments found hair RCH!as the standard for measuring larval settlement indifferent areas. However, when m PugetSound. suspendedinhigh settlement areas, not only did the RCH pads receive settlement, sodid the Larvalrecruitment of tftytr'lus eduits was monitored by counting the number of plan- PVCpipe frames towhich they were attached, therope on which they were suspended, and tigrades newly settled mussel larvae! attached to coUectorsubstrates, CoUector substrates thenetting that supported theRCH pads. Itseems that mussels wiUsettle on anything leftin madefrom strips of RCHmaterial cut into pads and attached to framesof PVCpipe Figure9! thewater long enough. weresuspended byfloats or docksso that they were continuously submerged. Samples were Thekey factor involved incatching seed is the surf'ace texture of the substrate. Mus- takenmonthly or bimonthlyand coHectors replaced with a newRCH pad. sellarvae prefer to settle on filamentous substrates, suchas rope hemp or coir! that has a CountingSamples bristlytexture, or a PVCpipe that has diatoms andtor hydroids growing on it, giving it a Settledlarvae ofiffytttus edtdis were removed from the coUectors by emersing them filamentoustexture, Data provided byJohnson 980! suggestthat hydroid and diatom in householdbleach for eightminutes, Bleach oxidizes the mussel's byssal fiber attachments, growthon coHecting substrates dramatically improve their larval collecting capabilities. Since therebyfreeing them I'rom the collector. Simply rinsing the coflectors over stacked sieves, inmost areas of Puget Sound hydroids or diatoms wiH grow on submerged substrates in a one-miHimeter 18! and0.150-mfllimeter 100! meshsize would retain newly settled matterof weeks, many methods can be used to obtain seed. mussels,Counting of plantigradeswas done under a microscopein petri dishes,When sam- It isonly necessary tosubmerge coUectors forone month or a fewweeks to obtain plescontained more than 1,000 plantigrades perRCH pad, subsamples were taken to esti- theproper settlement ofhydroids ordiatoms, Thus, the most important criteria are placement mate their total number, wheresufficient settlement isexpected and that the rope is hbrous,or has enough time to AreasSamplezl acquirethe proper texture to attractmussel larvae. It isapparent that the most cost-effective method of obtainingseed is to catch it on The17 sites studied by Johnson 980! andSkidmore 983! werethe following iinesrather than scrape it from rocks or pilings.Tocatch seed, it is necessary toknow when Figure i0 a andb!: thepeak settlement ofrnussels occurs and where the most likely settlement areas are. ReaUz- 1. BuddInlet, Department of NaturalResources marine station floating dock ingthis need, two studies conducted bythe University ofWashington weremodeled todeter- BuddInlet, West Bay Marina minewhen peak settlements occur for different areas mPuget Sound and what areas offer the 3. CaseInlet, north sideof HerronIsland bestor mostconsistent settlement of mussellarvae. The results of thesestudies are described CaseInlet, one mile north of ferry landing in thefollowing section. 5. DabobBay, Point Whitney shellfish laboratory dock 6, DabobBay, Camp Parsons dock 7. EldInlet, near The Evergreen State College MusselLarval Settlement in PugetSound 8. FoxIsland, Washington State Department of Fisheries salmon net pens Twoseparate studies to determinewhen and where mussel larvae settlement occurs 9. Graysmarsh,wildlife refuge, Strait of Juan de Fuca, Sequim Bay monitored17 sites and included most areas that could feasibly support a musselculture 10 HolmesHarbor, dock near golf course 11, Manchester,Naflonal Marine Fisheries Service laboratory dock, east side Figure9. Rubberizedcurled 12. Manchester,NMFS laboratory dock, westside pacifyinghair RCH!pads and one- inchPVC frames, which are used lo 13, PennCove, Coupevifle dock, gas float rnonrtorthe settlement of Nfybios 14. PennCove, Penn Cove Mussels, Inc. raft eduiislarvae in PugetSound 15, PennCove, San de Fucadock 16. PortTownsend, Union wharf 20 cm 17, SquaxinIsland, Squaxin salmon net pens in PealePassage Seasonal Patterns of Settlement Themajority of settlementoccurred from late April through early July for thehvo yearsstudied. Figures 11-1 5 showthe seasonal fluctuations of Mytilusedutiv larval settle- mentfor thestudy sites. Most sites displayed the characteristic rapid increase to peaksettle- mentlevel, then a gradualdecrease within two to sixmonths, By winter the majority of the . studysites had virtuaHy no mussellarval settlement activity. 17 16 ~ifureelAquacuilurein Puget Sound SeedColleclton in PugetSound CANAOA 'Ev Figure1GA. NorthPuget Sound and the San Juan Archipelago. ' indicates study site. Figure10B. PugetSound and Hood Canal. indicatesstudy site. 18 heedCottectton rn PugetSound JttusselAquaculture in Puget Sound Figure11. Numbersof Mytrtus 03000 Figure13. Numbersot My/J!JJs eduiislarvae settled at BJJddIr lei 50,IXI0 edorislarvae settled al lhreesites in andCase Inlet. 50OR PennCove, Whidbey Island, Wash- 70XO ington. 30.RO 95 200R JODIMI 10, 20OR 10'JOI J 191J 1990 20 50OX Figure14. Numberof Myfiirrs eduiislarvae sett ed in HolmesHar- JJ bor,Whidbey Island and on the east 10 sideot SquaxinIsland dunng 198. 100 IXI 1979 20000 CC Figure12. Numbersot My i!us edunslarvae settled at DabobBay '50Xi 10000 andManchester. 10 1979 Figure15. Numbersof Myriius 3 000 cdogssettled at EldInlet, Port Townsend,and Fox Island during 1979. J 7 M 1979 1980 2000 000 OR M J 7 M 9 M 3 J 9 1979 1979 1980 2t 2D ,4fum>/Aquaculturein Pugef Siiund ,'yeedC'olkciionin Pugel Sound Table2 showsthelargest numbers ofmussel larvae collected for1979 and 1980 and Table2. PeakSettlements of Nfytifua eduiiS larvae and settlement periad fOr variOuS areas Of Pugot Sound approxunatesettlement times. Most sites had peak settlements oflarvae during late spring or 1979 1980 earlysummer. Some sites had not one, but hvo settlement peaks, with one occurring inlate Plaatigrades Settlement Plaotigrades Seiuemeot springand another in latesummer or fall. Locatipn peroolleotor period personestor period Settlement Densities BuddInlet Numbersofplantigrades perRCH pad varied from area to area. Peak settlements A! nept Nat Resources 22,500 May-June21 23,200 May8-22 B!West Bay Marina 50,300 May-June21 21,640 IVIay 8-22 rangedfrom 472,500 plan igradesonan RCH pad in Penn Cove to232 per pad in Manchester CaseInlet east!,The ranking ofpeak settlements froinall sites reveal large variations insettlement in A! !terranIsland 12,400 lateMay-June 15 4,260 lateApril-May 15 PugetSound see Table J! 8! Shaws 34,500 lateMay-June15 8,930 lateApril-May 15 In 1979Penn Cove had the highest levels of mussel larval settlement ofaII areas nabobBay A! Pl Whitney 6,360 August-Navember 7.520 lateApril-May 23 studied.Counts ofplantigrades were472,500, 201,500 and 79,900 plantigrades percollector 8! CampParsons 16,300 August-September 4 124 lateApril-May 23 padfor the three areas studied inPenn Cove. These were found to he adequate, ifnot too Manchester A! East 236 lateJuly 227 lateJuly-August dense,for useby mussel growers in thatarea. 8! West 862 lateJuly 453 lateJuly-August In 1979and 1980 Table2! therewas a largedifference in settlementon PennCiive PennCove MusselsInc. rafLs, although owner Peter Jefferds expressed satisfaction withthe sets. In fact, A! Coupeviliedock 20I,500 aleMay-June 15 13,600 lateMay-June lateJuly-August inboth cases the settlement required thinning because they were too dense for uninhibited 8! PennCove Mussels, inc 79,900 ateMay-June 15 3,876 IVIay-June growout.Four thousand plantigrades perRCH pad could be considered a viable coinmercial C!San de Puca dock 11900 May-June Augusp settlement.However, areas with higher settlement levels are more likely to receive aconsis- September tentsettlement than thoseon thelower end of thescale, HelmesHarbor 57,800 lateMay-June WhySome Areas are Better than Others Seuaxlalslead 6,900 May-June EldInlet 3,200 lateMay Becauseofthe wide range of physical properties contained in he areas studied, October-November somegeneralizations canbe made as to what makes upa goodsite for catching mussel PorITewasead 1,600 July-midSeptember larvae.Settlement wasgreater inprotected bays and inlets, where the newly spawned larvae Foxisland 336 lateSpring-early summer wereless likely to be sv, ept away by tides, currents, orwind-created mixing. Graysmarrh 264 lateAugust-November PennCove had the highest larval settlement rateof afl areas studied. It is a protected Table3, Rankingof sitesby numbers of plantigradesat "peak settlement" for 1979.Indicated andfairly stable body of water, has a slowflushing rate, and during spring and summer there numbersare an average of 2 or3 RCHpads. islittle wind-created mixing. Nearby, theSkagit River introduces nutrient-rich v'ater that siowlyenters the Penn Cove system, Enormous diatom and dinoflagellate blooms continue SampleSite PlafstigradeS/RCHpatl nearlyall spring and summer. These blooms feed a largenatural mussel population and supplylarge swarms oflarvae with adequate food, A greatproportion oflarvae are able to 1979 1980 PennCove, Juan de Fucadock 472,5 'I1,900 surviveand remain in thecove long enough to settle. PennCove, Coupeville dock Manchester,bycontrast, had the lowest settlement rate of the study areas. Its waters 201,500 13,800 PennCove, Perin Cove Mussels inc. raft 79,900 3,876 arealmost always well mixed, stratifying only on neap tides during long warm days in sum- HolmesHarbor, Golf coursedock 57,800 mer.It ispart of Rich's Passage, which isa flushingchannel forPort Orchard and Sinclair BuddInlet, WestBay Mar na 50,300 21,640 Inlet.Thus, any larvae spawned atManchester arelikely to be swept away or mixed into the CaseInlet, North of Ferrylanding one mile! 34.500 8,930 waterto produce only sparse concentrations. Thetiming of settlement isalso affected by Buddinlet, Departmentof NaturalResources dock 22,500 23,200 DabobBay, CampParsons 16,3DG 4,174 physicalproperties of thewater. CaseInlet, HerronIsland 12,400 4,260 Johnson 980! foundthat there was a gradientintiming of settlement from the SguaxinIsland, Salmon net pens 6,900 extremeinlets of southern Puget Sound and the Saratoga Basin tothe Strait ofJuan de Fuca. DabobPay, Whitney Pt. Shellfish laboratory 6,400 7,520 Inhis study the earliest settlement occurred inthe spring insouth Puget Sound and Saratoga EldInlet, near Evergreen State College 3,200 Basin,Settlement wasincreasinly later at Fox Island, Manchester, Port Townsend, and Grays- PortTownsend, Union Wharf 1,600 Manchester,West 882 453 marsh.Essentially, themore influence from the main basin waters, the later the mussel settle- Foxisland, Washington Dept. of Fisheriesnet pens 336 ment,Settlement peaked insummer inthe main basin of Puget Sound and Strait ofJuan de Graysmarsh,Wilcf life Refuge 264 Manchester,East 232 273 Seedr.olleciion in Puger,i,ound NusrelAquaculture in PugeiSound rialinfections of Vibrio anguillaruzn. In aU, 914,000 setting-sized larvae were produced Fuca.Lower water temperature closerto the Strait ofJuan de Fuca may have paaiaffy ex- from206 rniffion fertilized eggs. The maximum recorded survival I'rom egg to metamorphosis plainedthe delayed settlement times. stagewas 1.14 percent for aUexperiments. LarvalSettlement Prediction Model Settlement Johnson 979! found that itwas possible topredict thetime ofmussel larval settle- Threesubstrates were tested in thetanks for their ability to catch settling mussel arvae.They were Synclove rope, RCH material, and fiberglass filter material, all of whichhad mentbyeither correlating degree-days thatthe larvae were present inthe water orby count- a filamentoustexture required for settlement. Although the preferred settlement substrates ingthe number of eyed larvae in the water. werefilamentous, a large proportion oflarvae 0-74 percent!settled on the sides of the TetnyeratureModel tanks,which offered the largest surface area for settlement. Ii wassuggested inthe literature andfound bysampling inPuget Sound that the lengthoftime larvae arefree-swimming beforesettling isaffected bythe temperatures they encounter.Warmer v'ater generally hastens thedevelopment ofthe larvae, concluded by Bayne,1965! up to 14'C, However, ifthe water iswarmer than 14'C no significant increase in developmentoccurs,Johnson calculated a value of496 day-degrees forfuU development and settlementI'or mussel larvae inPuget Sound. This value iscalculated byadding the daily temperatureofthe water from the time ofmussel spawning tothe time ofIlval settlement. I.arvaein HolmesHarbor settled after five to sixweeks. CorrelationofEyed Larvae to Settled Larvae Johnsonalsofound ihe number ofeyed larvae occurring inthe plankton wasa good indicatorofwhen settlement would occur: in Holmes Harbor, for example, anincrease in eyedlarvae vvasrapidly followed bya sharpincrease inlatvae settling. Thenumber ofeyed- larvaeinthe plankton increases sharply before settlement. Theterm "eyed" larvae refers toa conspicuousdarkspot that appears inside thesheU ofthe free-swimming larvaebefore they beginsearching fora sitetosettle. This spot isthought tohave some use as far as orientation tolight. Settlement timescan be estimated closely using water temperature andeyed larvae counts HatcheryRearing of Nytfkcs edglis Larvae Atthe onset of the mussel culture studies atthe University ofWashington, catching wildseed was a majorobstacle withthe two sites selected. Researchers therefore decided that toobtain consistent supplies ofseed itwould be necessary toproduce it ina shellfish hatchery.Waterstrat 979! experimented withrearing,tent tilusedulis larvae tosetting size at theNational Marine Fisheries Services laboratory experimental hatchery inManchester. MJiilusedulis were difficult tospawn. Tomduce spawning themussels wereplaced inelevated seawater, 18-2>'C, for up to two hours. If this did not induce spawning theywere treatedwith chemical stimulants, KCI gramsper liter!, H202 Morse etal., 1977!, and spermsuspensions obtainedby stripping malernussels. Normal fecundits wasfrom 500,000 to 6 millioneggs per individual. Onceeggs were collected theywere fertilized witha smallamount ofsperm, andheld in 150-litercircular tanks in a staticwater system at15-21'C. Densities oflarvae inthe tanks wereless than five per milliliter at the straight hinge size. Survivalrates of larvae from egg to straight hinge stage was 1$.5 percent; from straighthinge tosettlement sizesurvival vtas3.3 percent. Several batches werelost to bacte- .Itu,ccetrtquacutturem Puget,S'ourrd tr'rrur' h.,ttortrrtr'ti,arid rfnrhtion ter,and Penn Cove, and analyzed using methods described byStrickland and Parsons 972! Growthwto todetermine the weight of microscopic materials present, Particles used by rVytilus edtdr's as foodare 5-250 microrneters in size. Only particles within this size range were used in food Iv o comparisons.Studyareas were compared, estimating thefood available bythe dry weights of h e retainedparticles, Total particulates dry weights! and particulate organic material ashed I 5 C3 v eight!were determined Bavne and Widdows. 1978!. 3 Growth Results .V!tilus educ's, grown at four of the live experimental sites in PugetSound, attained market-sizedsheU length 0 millimeter!within 12 to 15months. Mussels grown at Man- !r '9 C 3 r 'r 3 r, 5 n 9.9 9hC chesterwere the only group not to attain the average size of 50miUirneters even though they v weregrown for 18months. Growth rates of.Vytilus educe's forthe five areas are shown in L II Figure17. Since seed mussels for aff five sites were collected from the same area Budd Inlet! andgrown in identicalcages, dilferences ingrohtnh rates were auributed totheir growing 5 X environment. ?e 5 c3 3 Lipidgrowth rates occurred during the hrst summer and faU with the most pro- nouncedgrothnh between the sizes of 15and 85 miffimeters. In some areas the most rapid growthwas during October and November. When observing increments ofgrowth per month it waspossible tocategorize thegrowing areas into two distinct groups Figures 18a and b!. IvV 195C Slowergrowth areas Figure 18a! were found to have a decreasinggrowth rate through the experiment,while the higher growth areas Figure 18b! had "growth bursts" during October Figure18. Averagemonlhly growth incrernenls in shelllengths ol lirfyfrloserfulrs grown at hve ocationstn C 5 andNovember. Growth increments per month reached 12,6 millimeters per month during the Puge'ISound Ie! is lheslower growth areas, and fb!, faUmonths in highgrovrih areas, while a maximumofsix miffimeters per month was mea- having"grOwth bursts" in!all arethe taSter grawth suredin theslower growth areas. One possible explanation forthe different grosvxh rates was areas thefood found in thoseparticular areas of PugetSound. Figure! 9. Righr:Parlicu ale Organic rnatter POM! SeawaterAnalysis fromone liter semfh es taken from e!Case Inlet, fb! Manchesler.and fc! PennCOve Particulateorganic matter POM!, as a fractionofthe seston in seawater,can be construedasa grossindicator of availabiefood to filter feeding animals Widdows, 1978!, herelatr.d to theamount of foodin thewater, After sampling v aterover eight months from CaseInlet, Manchester, and Penn Cove showed that POM varies for differentareas of Puget Sound Figures 19 and 20!, Penn Cove had the highest POM weight with 8.56 miUigrams per PennCove and Manchester for POM,it becameapparent that there was more food available to literduring mid-August. Manchester hadthe lowest seasonal maximum ofthe three areas musselsas POCMand total seston in Penn Cove than at Manchester. Duringmost of the year Penn Cove waters are turbid, rich, and light-green incolor. studiedwith 4 miffigramsperliter. However, Manchester had the highest percentage POM of TemperatureIrr'adienLs andsalinity dilferences can be detected in its surface layers. Dense totalseston, with 8i percent.Maximum weight of totalseston was 10 miffigrams per liter layersof phytoplanktonand suspended particulates can be seen while scuba-diving. These recordedin June in bothPenn Cove and Case Inlet. v:arm.nutrient-rich surface layers support large blooms of phytoplanktnnthat feed the FactorsAN'ecting Growth rapidlygrowing mussels. The clear, deep blue waters at Manchester, however, are well-mixed 34ytilusedulr'sn being a filterfeeding animal, is dependentupon plankton, organic andexchanged daily with main basin waters of Puget Sound. Only rarely at Manchester willa detritus,bacteria, and probably dissolsed organic matter DOM! in the water as sources of thermoclineor halochne develop. Suspended particulates and plankton are weU mixed into food.In aquacukureoperations, population densities, grov;ing depths, and predation can be thewater column and rarely form dense aggregations. Thus, large blooms of phytoplanktonto controffedtooptimize growth, but food supplies can only be reasonably controUed through supportfast growth are rarely available at Manchester, siteselection. Therefore, to assurefast grossih, mussel aquaculturists must locate their opera- Mortalities tionsin productivebays. In thisstudy the growth of mussels was compared tothe amount of t'ood in thewater, At 18months of age,the average cumulative mortality of musselswas approximately representedhytotal seston and POM, Faster grovih rates and larger ultimate size appeared to 80 percent Figure 21! for aUfive areas tested, After six months of theexperimentsome mortalitieswere seen at Manchester.The other four areashad no signilicantmortalities until 28 ,ItuswlAquaculture in l'upet'Sound Grvulh, .4IVrtutitV, and Vrutitr'vn eacharea and placed in cages covered with vexar I -inch plastic nettmg to protect them Condition Index againstpredation. Arrays of duplicate cages with rnussels from the three seed sources were Conditionindices can be considered a measureof "marketability"or "fatness"of a setup at eachof thethree test growth sites during February 1981. bivalve,or moreprecisely, the tissue weight relative to shellparameter. At times,the meats of Results musselsare extremely small doe to spawningor otherconsiderations, which reduces their PennCove PennCove seed produced the largest mussels over nine months Figure marketacceptance. If detected, it may be prudent to restrictthe harvest of musselsduring this 22a!.The growth curves are a typicalsigmoidal shape inherent to thegrowth characteristics period.In Belgiumand other large mussel-producing countries, harvest is suspendedduring ofmany bivalves. Figure 22a shows a dropin thesize of mussels from Penn Cove during andafter spawning. In fact,mussels from wild sobtidal beds on theeast coast of theUnited SeptembertoNovember. This was due to starfish intruding into the cages and eating the Statesare not harvested during the summer months due to poormeat condition due to largermussels. However, until the starfish invasion, Penn Cove seed had exhibited faster spawning. growththan the other two populations, in PugetSound mussels follow distinct condition patterns related to watertempera- Meatcontent of musselswas also compared dry meat weights per mussel! for the tureand food regimes. Johnson 980! andWaterstrat 979! studiedthe condition index of threeseed sources grown at Penn Cove. At Penn Cove dry weighLs ofthe three seed popula- PugetSound mussels. Some generalizations fromtheir work are made which are presented in tionsdid notdiffer significantly at theend of thestudy. thefollowing section. Survivalofmussels grown at Penn Cove was also affected bystarfish predation Fig- ure22b! . Likegrowth rate, survival among Penn Cove mussels was superior until the preda- Condition Index Evaluations tionindicating that Penn Cove mussels seemed tosurvive better, although survival for all seed Numericalvalues to expresscondition index can be obtained by using several meth- sourceswas quite low. ods.One standard method follows Westley 9S9!: .4frrnchesterTests show that the shell lengths of thethree stocks of mussels grown D wei ht tissue rams! atManchester differed significantly in September,with Penn Cove seed attaining the greatest x 100 = Condition Index lengthand Budd Inlet the least Figure 23a! . Survivalwas found to be low in allseed sources Volume of shell cavitv ml! bythe end of the experiment, butPenn Cove seed survhed better although still low! than Usingthis method, an oyster is marketablewhen it hasa conditionindex value of 10or DabobBay and Budd Inlet seed Figure 23b! . Theseed sources also differed indry weights of greater.A similarvalue is as yet undetermined for musselsin PugetSound. meatat the end of theexperiments. Dabob Bay seed achieved greater dry weights than Penn Conditionindex of musselshave, in thepast, been based on severalshell parameters: Coveand Budd Inlet seed, hqurzx'inisr randAt this site Penn Cove mussel seed again attained the largest shell Figure24. Growthand survival of musselsfrom lengthsand had better survival than the other two seed sources tested Figures 24a and b!. Ihreeseed sources grown at SquaxinIsland Musseldry weights diifered between seed sources with Dabob Bay having the highest meat weightfollowed by Budd Inlet and Penn Cove, In summary,the hest growth rates were attained with Penn Cove and Budd Inlet seed grownatPenn Cove and Squaxin Island. Seed from Penn Cove provided the best growth inall hieewater areas tested. In evaluating thegrowth potential ofthe three locations, Manchester is theprrorest, while Penn Cove and Squaxin were similar. Differencesin growth among the three seed populations in this experiment may be indicativeofgenetic dilferences. Electrophoretic techniques chemically plating chrorno- somes!have revealed differences in allele frequences in rnusselson the east coast of North Americafrom the intertidal zone Koehnet al 1973! in estuaries oehn et al,,1976!, and withinthe Canadian Maritimes Gartner-Kepkay et al,, 1980!.Thus, it is verylikely that dilfer- encesin geneticmake-up caused the variations seen in thisstudy, Thepossibdity ofhnding a superiorgrowing or survivingmussel for culture is an importantfactor for a musselaquaculturist toconsider. A superior seed source could benefit theemerging mussel aquaculture industry. Though transferring seed from one site to another islabor-intensive, thebenehts from faster growth and better survivorship may far outweigh the additional labor costs. I},' .ttuhxeiAqrur<'uiture in Pummel.'iound h'rOtcth..UOrlcriilf, ct nd CO>rch'ti'mr 5o Figure26. CondmonIndex of mussels,Mytrrus Figure25. Conditionindex of edv/rs,al eighlIOCali One in PugefSound adult,raft-53SOended IVfytrtvs edvtiS 40 at Seabeckarid Manchesfer Calcu- '2 latedby f!ry tissuewl grams!'vol. 30 of shellcavity lmlll x f 00C I 2O H 10 5o u I 3 h, 0 N 3 i F v 4 40 Wh volume,weight, and length, AH of thesemethods have some degree of errorinvolved in their 3O calculations.In thefirst experiment, Waterstrat used Westley'5 method for determiningcondi- tionindex of musseisgrown at Seabeck and Manchester, For the sec 34 Gr indicatedthatrtfytiluseatiforniar rotstarpamcproductwsn Swvavas Figure28. S ~rvival of lirfytrlus edulrsand Vyfdus ealilomrarrus grownat Manchesterand Sqfraxin Island ore29. Iolar OrganicPrO- CtinnfTOP'I Of MyrrluS edulrS and I,luS Caldomi anus grown at lUlan- slerand Squaxin Island r I, upswingat birthloctions, and attained the highest TOP value of 125grams per 100 rnussels. theaverage organic value of a musselat the shell lengths calculated at eachsample period, ,Ceuuvzterctncd>sisSquaxin Island and Manchester have substantial differences in TheTOP value obtained is essentiallyan estimate of theorganics that were accrued by the v aterproductivity: Squaxin Island is byfar themore productive. Its waters are very green and populationof 100mussels, taking into consideration loss of organicsfrom mortalities. it is possibleto seeplanktonic cells in the v aterat times.During the springand summer there Atboth sites the amount and types of particnbtematerial in thewater available as aredefinite phytoplankton blooms that make the water turbid and rich looking. Manchester, foodto musselswas sampled, Samples were taken using the methods described by Strickland on theother hand, lias very little phytoplankton in the water. For most of theyear, it is clear andParsons 9?2! for determiningthe weight of microscopicmaterials in seawater. andnonproductive. During the summer sonic large blooms appear, but they often disappear Results asfast as they come. Figure 30 shows the total weight of seston.POM in grams,and the ShellLengths Shelllength measurements revealed that at both sites, N edulisini- «verageparticle sizes for seawateratManchester and Squaxin Island. At Squaxin Island there tiallygrew faster for thefirst three months. but by August growth of tt edits beganto slow wasmore total seston,and therefore more particulateorganic matter, which meanttnore down Figure27!. Bythe termination of theexperiment the difference in sizebetween the two foodwas available for filter feeders,This maybe responsiblefor growthdifference observed specieswas small. Average shell lengths and 95 percent confidence intervals are as follows: hetweerrthe two sites. CulturePotential of Nytklus eaAforw&nats SquaxinIsland Manchester Harvestingof,tfytilus ccdtfornianusfrom the outer coastof Oregonand its success- M. californianus 47.8mm + 1.59 <0.6mm + I.48 ful introductionto severalwestern markets lends credence to thepotential marketability of M. edulis 48.3 mm + 7.6 8 months! 45,6 mm + 1.65 thisorganism if cultured.Since some areas in PugetSoundcannot support culture of bay Suruitval Survivalwas similar at both sitesbut dissimilarbetween species Figure mussels,the California mussel may be a suitablealternative, 28!,M, cabfornianus showed loN mortahty throughout the experiment and at no time did Although,V,edulis growsfaster than It. cctlifornicanus,both reacha harvestablesize manydie at once,,st, educ's, on theother hand, only survived well until June, when mortalities in approximatelyone year Chaves,1975; Chaves and Chew, 1975; Johnson and Chew, 1982; beganto appearand increased until, hy September, there was only one survivor remaining at Skidmore,1983: lncze and Lutz, 1980! . Drytissue weighb for a 50-millimeterrtl. cahforni- SquaxinIsland and only slightly more than 20 percent at Manchester.Predators were not a anusare slightly greater than à edulisindicating that a highermeat iield aftercooking is factorin eitherlocation as the mussels were grown in liow-throughcages and at notime did obtainedfor r>L caltfornictnus, which is a desirabletrait to a restauranteur.Shell weights of thepresence of commonmussel predators become apparent. At timesof mortalitiesfreshly cultured.M.culifornianus, however, are nearly twice that of culturedrti. edulis,but this may deadmussels could be found gaping open with the partially decayed tissue still in the shell, hean asset because it may allow for mechanicalcleaning. Penn Cove mussels are presently TotalOrganic Production Growthol'bivalve populations have often been ex- strippedfrom culture lines, separated, and cleaned by hand. The shells of,V. edulis are so pressedasincreases in shelldimensions. Though this gives insight to shelfgrowth, it addsno brittlethat mechanical cleaning would cause too many shells to bebroken, understandingof a species'ability to utibzeib environment,fix carboncontaining energy A culturespecies that experiences 100 percent mortality before it reachesharvest substances,and survive. TOP values were used in thisstudy to supplementshell-length com- sizeis obviouslyunacceptable. At SquaxinIsland, an entireexperimental population of It. parisons.In thefirst two months of growth,N edulishad accumulated a higher TOP value at edulisdied by the end of thesummer. flowever, rV, californictnus, grown at thesame site in bothsites, but in June and July, because of substantialmortalities, they began to drop Figure thesame manner did notexperience the high mortality. Seventy-seven percent of thepopula- 29!.Conversely, TOPvalues for M californianus,during the same period, began a rapid GrOrrtb ftffrt«frtt «nd Crpndrtrrpn .If« Crei Arf fV«re ftfrre in Pnfaet.ylnr nd Table 7. Qo!ImaitemPeratures and salinities tor surviveof MyflfuSCafrfOrnianus larvae Temperature Salinity 3030 Ernhryontc 145 298 Day3 1 5.5 307 Day7 l61 393 Day17 147 30.6 14.7 30.1 Day21 al00 Table8. Oplimaltemperatures andsali ~ ibesfor growthof Mutt/uscairfornianvs larvae TemperatureeC Salinity'iao 206 Day3 1 5.9 308 Day7 17.9 31.2 Day17 143 31.2 Day2I 1 4.5 311 rangedfrom 26'i00 to 36'!'00 at 2'700 intervaL~. Survival and growth of larvae were measured 2300 atdays 3, 7, l 7,and 21. Greatest survival rates at each sampling are shown in Table7. .M.c«liforff ianffa larvae survived best at 14.7'C and a salinityof30 l pptfor the 2 l- 2C00 dayexperiment. Figure 31 shows a responsesurface fffr survival atthe 21-day sample: the 0 3 00 6 03 0 00 1200 Ielr 0 30 elI 0 ie00 2 00 30all centeris the optimal temperature and salinity for survival today 21. The center was consid- remperalereIr'i eredas having induced 100 percent survival and the temperatures andsalinities correspond- Figure31. Surfaceresponse of lÃytffvscalifornia«vs larva stfrvtvaf. Dptimal survival occurred at ingwith the rings around the center induced survival oflarvae, as indicated on the rings. centerwhere Temp. 14.7 C andsalinity 30.1 ppt. to day21. llarvalgrowth was also affected bydifference in temperatureand salinity, tempera- tureespecially, Temperatures andsalinities that induced the best grownh are shown in Table f!, grnwihresponse surface is shownin Figure32. Similartrends emerged in both survival and growth by varying temperatures and salinifies.in bothcases faster growth and hetter survival was apparent at highertemperatures nap whenthe }atvae svere young 7days! and as the larvae became older l 7-21days! the trendreversed and the larvaewere enhanced by lowertemperatures, 3e00 Settlement In Falmagne'sexperiments, the,V c«lrforffianf46 larvae were ready to select a sitein whichto settle at 17-2i days from fertilization. This was marked first hy the development ofa 3203 conspicuous"evespot" and finaliy a ciliatedfoot. Like many other bivalve larvae, the develop- mentof an eyespot indicates the approaching settlement from the free-swimming stage. Just ," 00 beforea settlementthe ciliated foot appears at thispoint the larvae is termed"pediveliger," whichis usedin thesearch for a siteon which to settle.Eyespots developed when the larvae lf 00 were230-240 micrometers in sizeand larvae remained approximately this size until settle- ment.When the larvae settle, they attach themselves with a byssalthread. MetamOrphOSiSOftf, CahfOrni«neer frOmfree-swimming larvae to that Of SeSSile, 2!00 attachedmussels has been the most plaguing factor in attemptsto "set' larvae.Larvae sur- vivedto near the time of metamorphosis, atwhich point substantial mortalities occurred. ar.00 Duringmetamorphosis larvae lose their velum a ciliated circular organ used for swimming 600 e00 lllx 1006 0 I 21JU a ll 2 Hl lp 10 andfeeding! and begin life as attached organisms. Nofeeding occurs during metamorphosis; acmelalaic I6, energyrequired for physiological rearrangement comes from stored energy reserves which Figure32, Surfaceresponse of fprffrfiivs catifornianus larva growth after 21 days of hatchery culture. Optima arelipids. lf thehpid level is iow, the larvae may not survive Gallager and Vlann, 198 t! . growthoccurred at centerwhere Temp. 14.5 C' andSalinity 31.1 ppt ,ftuael2tqtuiculturein Puget bund G'routb. dtlortaiit>, and Condition Oncethe metamorphosis iscomplete themusseis again begin to feed. Figure33. MyiiluSCaiiiarnia2ioS laNaI Sett emeot Settlementattempts have thus far met with limited success, Many techniques and ootwo types oI collectorsobstoites and tank sides. diferentsuhstrates have been used to increasethe numbers of larvaesettling However, in mostattempts thefinal number ofsettled larvae were unacceptably low. Sc~eralattempts were made toenhance thesettlement, N californianus wasfound tnprefer the same filamentous typecollector substrates thatIf. edulis preferred. Figure 33 showsthat, of the three substrates available forN caltfornianustosettle on, it choserubber- izedcurled packing hair, which was the most filamentous. Apeculiar trait that,'lfcahfornianus displayed when searching fora settlementsite wastheir habit of dropping tothe bottom oithe tank. Most of the pediveligers could be found atthe bottom of the tank, When collector substrates were suspended in the tanks most of the settlementwould occur towardthe bottom of the substrate. Othertechniques usedto enhance settlement were conditioning thewater by placing d 2 d3 adultmussels in it beforeintroduction ofthe larvae and by decreasing thetemperature ofthe waterduring settlement attempts, Themost significant effectwas induced bylowering the ~III' ! watertemperature, onedegree per day, to 12'C.Survival oflarvae after metamorphosis was tionsin I'ugetSound are not limiting to thereproductive capabilities of2IS. californtanus, bestusing this procedure. 3, If it is possiblefor N californianusto spawnin PugetSound, he next considera- Experimentstodetermine lipidreserves bystaining Gallager andMann, 1983! and tionis whether the larvae can survive and settle. Very little information isavailable onpre- iodevelop new techniques toenhance setUement areunder way. These experiments mayshed ferredsubstrateand larval behavior, The Uiniversity ofWashington SeaGrant supported lighton the reason forhigh mortalities oflarvae during metamorphosis, Ifthe cause islow hatcheryai ihiMFS aquaculture facility in Manchesterhasbeen unable to successfully reara lipidreserves, thentechniques toalleviate thisproblem canbe researched. largebatch of larvae past metamorphosis. Possibly conditions in Puget Sound limit the range BiologicalConsiderations of,tf californianus by exclusionof thelarvae, Introductionofexotic species inPuget Sound isnot a newoccurrence, In1924 the Reproductivestrategies between mussel species are quite diNerent,.tf, edulis is a seedof the Pacific oyster Crassostrea gigas! was introduced toPuget Sound toaid the massspawner, releasing large numbers of eggsin thespring. M californianusappears to be failingand over-harvested Olympiaoyster. Not only did the Pacific oyster adapt weH on the atrickle spawner v ith no predictable pattern of spawning seen. Gompetition forspace in westcoast of the United States, so did some associated plants and animals were introdure d PugetSound is keenerbecause of reducedwave action. so spawning characteristics ofAL alongwith the oyster shipments, Forexample, Japanese littleneck clams Tapesjaponica!, californutnusmay not be a successfulsurvival strategy, its"trickle" spawning characteristics nowcommonly found on many south Puget Sound beaches andhighly desirable asa commer- imroduceonly low numbers of larvaeinto the ecosystem compared to IXedulis, thus it cialspecies, wasintroduced along with a troublesomegastropod, Ocenebrajaponica, the dependsupon availability of suitablesites and colonization of spacewould be minimal. Japaneseoyster drill, Both species have had an economic impact inPuget Sound, one positive 4. Assumingthat.ti. californianus spawns and its larvae survive and settle, their andone negative, Thus, introduction ofnon-native species, such as M. caltfornianus isap- eventualsuccess or failure will depend on competition with other species, especially,tf. proachedwithgreat caution. While the exact outcome oftransplantingdV, cahfornianus into edulis.ILs success will bedictated by its suitability to copewith its environment and its PugetSound isnot known, possible adverse effecb should be considered. iwlnerabilit!to predators,It is possiblethat it cansurvive in someareas and not others due to Johnson 981! notedthe follov'ing considerations whenevaluating thepotential thelarge environmental diNerences throughout Puget Sound. outcomeofintroducing,IL californianus in oPuget Sound aquaculture: Harger 968, 1970a,b, and c. 19,2a and b! performedmany studies on the inter- I, Therange ofN californianusextends along a majorportion of the Pacific coast actionsand coexistence of the two mussel species in southernCalifornia. He found thathtf, ofcnorth America. Harger 9, Ob!states that it doesnot generally inhabit pi'otected waters, educ' maintaineda competitive advantage over,ll, californianus in quietwater situations butdoes occur sparsely t'nharbors, ihus M californianusmay not be successful inPuget becauseofits crawling behavior..lL edulis crawls to the outside of a clump,leaving 2'. Sound.However, thismay be an oversimplification sinceits culture here may overcome the californianus on the inside thereby restricting itsgrowth and eventually smothering it in silt. In theexposed environmenb ofthe open coast,tf. californtanus holds the advantage byits mechanismsthat exclude ib colonization. abilityto remainattached during severe winter storms. N edulisis more susceptible to 2, 3f.cahfornianusgrown insimulated culture conditions grows well and survives predationand wave force. in areaswhere Af. edulis does not. Well-developed eggs were observed under microscope in a sampleof,il, cahfornianus from Squaxin Island. The above findings suggest that the condi- 5. Threemeans of exclusionof,tf, caiifornianus from Puget Sound must be as- , tt Predators Starfish Predatorsthat consume mussels can cause substaniial losses to musselculturisb. Starfishconsume mussels and other shefllish as part of their normal diet, In Wash- Themost common predators are scoter ducks, s arfiish,and crabs. ingtonthe use of rafts and floats for mussel aquaculture deterslarge starfish from reaching Scoter Ducks cul urelines, hut it ispossible for free-swimming starlish larvae to settle on culture lines, At PennCove Mussels, Inc, lar Pollutiou Historicafly,themost significant impacLs onshellfish culturing areas have been the S 50 it@,srrqAquaculturer r Puget,you& Addi'trnrrat 'orrrrderatr'nns Fouling Budd Inlet Thefouling of culturedmussels can be a considerableproblem. Sett}ernent ofvarious An intense settlement of ban acies v as seen at Budd Inlet as at Penn Cove.It speciesofinvertebrates canadd substantial weight to culture ropes in andout of water, and comprisedthe major portion of foulingweight during spring nearlyhalf the weight of the requirescostly cleanup or removalatharvest. Some settlements ofinvertebrates cangrow and culturestring was fouling organisms!, Fouling weight during the summer was only two per- actuallystart preying on themusseLs, asmentioned earlier with starfish settling on mussel centcompared to 99 percentin thespring, Fouling was Irrw during the autumn with the culture lines, foulingorganisms comprising a maximumof sevenpercent oi themussel weight. The fouling Johnson 980! notedthe types and amounts of foulingorganisms found during communityduring the summer and autumn included polychaetes, nemereans, flatworrns, hy- differentseasons at PennCove, Manchester, and Budd Inlet. These locations are summarized drotds,barnacles, bryrrzoans, and anemones. as follows: Rejectsof IntertidalConditioning on Raft- Penn Cove Foulingin PennCove varies with depth and season. Barnacles settle heavily m the or Longline-GrownMIIssels to ColdStorage Survival springand comprise up to 74 percent of the mussel weight over thr ee months Settlement of Raft-r>r longline-grown musseLs are a highquali vproduct, but because they are barnacleswas greater at depththan near the surface. continuouslysubmerged while growing, when out of water hey have a relativelyshort shelf Foulingduring the summer was much lower than spring, only six percent of mussel life,Proper handling and storage of musselsincreases shelf life Slabyand Hinkle, !976!, but weight.Surface mussels were more fouled than at depth, Few barnacles settled during this "hardening"of musselscan also benefit shelf life. A commonpractice in theoyster industry is periodbut many other organisms were present: sea stars, polychaetes, nemertean worms to placeoysters in theintertidal zone where they are left exposed to air partof theday. This ribbonworms!, sea cucumbers, hydroids, flatworms, and bryozoans. The largest settlement processis referredto as"hardening" and is usedto increasethe oysters' ability to remain of invertebratesduring early summer was that of mussels.Mussel larvae settled on theculture closedvr h»e out of thewater, If anoyster or musselcannot remain closed. he liquor within lineson and between the larger mussels. Small mussels fouling the culture lines can cause a the shell is lost and the animal soon dies. considerableincrease in theamount of timerequired to cleanthe musseLs for market. ShelfLife of Intertidaland Continuously Submerged Mussels Manchester Preliminaryexperiments comparing the survival of intertidalmussels gathered f'rom Manchesterreceived the least amount of foulingof culturedmusseis. Seven percent floatsand subtidal mussels gathered from one foot above mean lower low water! show that of musselweight was the highest recorded weight of foulingorganisms found there. Seasons intertidalmussels have a farbetter shelf life johnson,1981!, Mussels were placed in a weresignilicantfy different and depths were slightly dilferent. Fouling was the heaviest atnvo- refrigeratorheld at IA'C. Intertidallygrown mussels remained alive far longerthan continu- metersduring the spring, because of barnaclesettlement, Bryozoans comprised the rnalor allysubmerged mussels, which began to dieat dayfl whileintertidal mussels did notbegin to portionof the fouling community during the summer, Although the weight of bryozoans was dieuntil day 11 Figure34!. Averagesurvival time was 15.6 days for subtidalmussels and lowtheir fouling was more significant here than at theother two stations, covering up to SO 19.3 dais for intertidal mussels. percentof somemussels at thesurface. Other organisms of thefouling community at this stationwere poiychaetes, green algae, hydroids, ascidians, flatworms, and anemones, igure34, fvtortait oty subt:dal ndintertidal mussels held in cold torage approximately 34'F, static!. ubtida!N 73,Intertidal N 5t. Foulingof musselson ropes in theintertidal zone by bamaces. ,ltuxvel Rejectsof intertidalHardening on ShelfLife FERKNCKS InJune 19BI, subtidal mussels were placed at theNational Marine Fisheries Service AquacultureFacility at iblanchester.Some rnussels were placed in basketssuspended from the pierat approximately sixfeet above MLI.W and some subtidally. After 2, 9, and 16 days of AquacultureDigest January,19144! Mussel», Robert Rosenberry, ed. 9 I!:46. intertidalexposure, the musseLs were placed in a coklroom and survival monitored Table B«yne,B.I.. f 1965! 'rowth and the delay of metamorphosis ofthe larvae of,Vy tilas edulis 9! I.ongerintertidal exposure did notnecessarily produce k>nger mean survival. With IG days L.! OPhelia2 I!: I 4",. of exposurean increase in theshelf life overthe subtidal control was seen, Ilow Jenkins.R.J. 9?9! Nussel cultivation in the.hturlborough Sound !yeu Zealand!, David Oceanleader ttagazine.Winter 1981.Seanle. Washington: Waterfront Press Co. JonesI.td., Wellington. 7S p Petrailis,P. S 974! Settlementpatterns of;liytilus edulis and Nytilus cahfornianus and Johnson,K.W. 9, 9!The relationship betv,'een Nytilus edutis larvae inthe plankton and theireffects on thedistribution of adultpopulations, M.S, Thesis, San Diego State Uni- settlementforHolmes Ilarbor, Washington. Thesis. University ofWashington, 45p. versity. Johnson,K.W. and Chew, K. 980! Cooperativemussel study: Annual Report 1979. Report Saunders,R,S. 984! ShellhshProtection Strategy. Washington State Department of Ecology, to theDepartment of Fisheries, 65 p, 38 p. Johnson,K.W. 981! Biological considerations forthe introduction ofNytilus californi- Seed,R, 975! ReproductioninNytilus Mollusca:Bivalvia! in Europeanwaters. Pubh'ca- anusinto Puget Sound. Report tothe Washington StateDepartment ofFLsheries. 11p. zione DellaStazione Zoologica Di,V'aPoti, Vol. 39, Suppl,I:317-334. Johnson,K.W., Chew, K.,and Sparks, P. 981! The influence ofintertidal exposure onthe Skidmore,D. A. 983! Settlement,Grov th, andSurvival of Nytilus edulis L in PugetSound coldstorage survival ofsuspended culture musseLs Nytltus eduh's! from Puget Sound. andAssessment ofitfytilus cahfnrnianus for aquaculture.M.S. Thesis, University of Reportto the Washington State Department ofFisheries. 20p. Washington.99 p. Johnson,K.W. and Chew, K. 982! Comparative growthof mussels coUected fromthree Slab>j,B. M. andHinlde, C. 976!. Handlingand storage of bluemussels in shell.Research spatiallyseparated populations inthe Puget Sound region. Report tothe Washington in theLife Sciences, Vol. 23, No, 4, Universityof Maine. StateDepartment of Fisheries.19 p, Soot-Ryan,T. 955! A reporton thefamily Nytili due Pelecepoda!,Allan Hancock Pacific Koehn,R.K., Turand, F,J.. and Mitton, J.B, 973!, Population genetics ofmarine pelecy- Expedition.20 I!:1-174. pods.II, Genetic differences inmicrohabitats ofmodiolus demissus. Etelution Strickland,J. D. H,and Parsons, T. R. 972! A practicalhandbook of seawateranalysis. 27; 100-105. Fisheries ResearchBoard of Canada. Bulletin 167. Koehn,R.K., Milkman, R.,and Mitton, J.B. 976!. Population genetics ofmarine pelecy- Suchanek,J. H. 979! The,tfytiluscalifornianus community: studies on thecompostion, podsIV. Selection, migration andgenetic differentiation inthe blue mussel Nytiyus structure,organization, and dynamics of a musselbed, Ph.D. Thesis, University of Wash- edulis. ington.268 p. Korringa,P. 976!Farming marine organisms low in thefood chain, Flsevier Publishing Taylor,R, Ph,D.candidate, University of Washington,GoUege of Ocean and Co.264 p. fishery Sciences,Personal Communication. Loosanoff,V.L. 943! Cultivationofthe edible musseI.,Southern Fisherman. January: Waterstrat,P,R, 9?9! Prospectsfor thedevelopment of a musselculture industry in Puget 10-27. Sound.Thesis. University of Washington.81 p. Lutz,R. A. 9?4a! . Raftcultivation ofmussels inMaine v aters: itspracticability, feasibilit! Westley,R, E, 959! Selectionand evaluation of methodsfor quantitativemeasurement of andpossible advantages. MaineSea Grant Bulletin No. 4. University ofMaine, Walpole, oystercondition. Proceedings tttational Shellfish Association 50:145-149, Maine.27 p, Widdows,J. 978! Combinedeffects of bodysize, food concentration and seston on the Lutz,R. A.: Incze, L S.;Chew, K. K.; Cliftou, J,A.: Haley, R.; Miller, B, A.; BrownneU, W.; physiologyofNytilus eduHs,Journal of NarineBiotogicat Association, United King- Chaves-Michael,L.;Blumenstock, M.W..; Hayes, K.P.; Weldon, A,; Dearborn, R.K.; and dom. 58.'109 124, Lloyd,P. 9? 7!, A comprehensivereviewof the commercial mussel industries inthe UnitedStates, Washington, D.C National Marine Fisheries Service, U.S. Government PrintingOffice, Stock No 003-020-00i33-S, 134p. Lutz,R. A. 980! Nussel Culture and Hareest: A ~Vorth American Perspeetiee. Elsevier ScientificPublishing Co, 3SO p. Magoon,C.D, andVining, R. 980! Introduction toShellfis Aquaculture in the Puget SoundRegion. Washington Department ofNatural Resources Handbook. 69p. Mason,J. 9; I! MusselCultivation, Underwater Journal 3;52 59. Mason,J, 976! Cultivation.p,385-410. InNarineNussels: TheirEcology and Physiology B.L. Bayne, ed.!, Cambridge: Cambridge University Press. 506 p. Morse,D,E., Duncan, H.;Hocker, N.; and Morse, A, 977! Hydrogen peroxide induces spawningiumolluscs with activation ofprostaglandin endoperoxide synthesase. Sci- ence. 196 5!:298-300. Myers,E, 981! The husbandry ofmussels ina Maineestuary, anappn>ach toa commercial enterprise,ILNH-SG-I64, University ofNew Hampshire. 45p. 57 Alsofrom%ashtttgtott Sea 'rttttt Guideto,tlanila Clam Arluaculture in Puget.Sound hi Oregor1 Attderson,' tart tt stillerand Kemieth K :hs~~ PacificCoast Clam Ftshert'es lh Tinatthlli Kelitttk.Katlmrine a ate ma.and Kemtetlt K. 1:hev Saltuonid Reproductionr An international,Stmposi um editedhy ltohert.'1 Ie amOtO and Staeta seteer ShellPshand Seauved Hanests of Puget,Sound hi [!anieiChenel and Thomas F Mumrord,Jr