水产养殖专业英语OceanTodayOpenRivers,AbundantFishManyspeciesoffish,includingthosethatareimportanttotheU.S.economy,migratefromtheoceantofreshwaterriversandstreamstospawn.Afterspendingyearsintheocean,fishinstinctuallyreturntothesameriverswheretheywereborn,makingtheoften-treacherousjourneyupstream.Somefish,likesalmon,travelnearlyathousandmiles.Iftheymakeitpaststrongrivercurrentsandhungrypredators,thesedeterminedfishmaythenfindthemselvesblockedbyman-madebarriers,suchasdams.AsmanyastwomilliondamsandculvertsarelocatedinthestreamsandriversoftheUnitedStates.Unfortunately,manyofthemblockaccesstomorethan600,000milesofriverhabitat.Special“fishladders”arebuilttohelpfishpassoverthesedamssotheycancontinueswimmingupstreamtoreachtheirspawninggrounds.Someofthedamsthatblockfishpassageareimportantproducersofcleanelectricalpower.Butotherdamsinthewayoffishmigrationsareoldandoutofuse,evendangerousiftheyareleftuncheckedandnotmaintained.Oftenthebestsolutionistotakethemdown.In2007,PortlandGeneralElectricremovedtheMarmotDaminOregon,whichopened100milesoffreshwaterhabitattothousandsofmigratingfish.Amongthemwereseveralsalmonspecies,whicharelistedas'threatened'undertheEndangeredSpeciesAct.TheMerrimackVillageDaminNewHampshirewasanothersuccessfuldamremoval.Thesmalldam,originallybuiltinthe1730s,hadfallenintodisuseanddisrepair.Loiselle:“RemovaloftheMerrimackVillageDamisgoingtomakewayforriverherring,Americanshad,Americaneels,andAtlanticsalmonthathavebeenblockedfrommigratinguptheSouheganRiverforalmosttwoandahalfcenturies.•••[bigsmile]weanticipatethatwe'regoingtoseemanymorefish,otherwildlifeintheareaandinourriversystemthanwe'veeverseenbefore.”NARRATOR:Whenweremoveabarriertomigratingfish,wenotonlyincreasethehealthandquantityoflocalfishpopulations,wealsoincreasetheoverallhealthoftheriverandeventheeconomichealthofthecommunity.NOAAhashelpedremoveover50damsin12years,enablingmigratoryfishtofinallyreachtheirhistorichabitat.FishonaFarmEveryweekendsmallfarmersaroundthecountryheadtotheirlocalfarmer'sma...
