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<br />
<br />
<br />occasionally even dl\.ertmg tlow Inw mland baSinS
<br />such as the Salton Se;t, The Color,ldo River Delta
<br />was further intlul'nced hy a rcm.ubhlt: tidal bUfr-.
<br />Tide:s In the SeJ. of Cortez t'xceed 9.0 m at the
<br />river's mouth, J.mong the hIghest In tht. wurld SWift,
<br />desuuni\'e tidal currt'"nts moved with rem,lrkable
<br />speed for more than 100 km upsueam,
<br />
<br />Low Desert. Riverine Fish Communities
<br />
<br />Canyons of lar,ge desert rIvers pn.-se:nt t\\O haslc
<br />types of habitat ~1ost Imprcssl\e >ltt. the reaches th.lt
<br />are termed wllltewater In the jarg\ln l,f river runners.
<br />where bonom lrrq,:ubntles cause wJ.vt'"s, whIrlpools.
<br />and other turDulenle. The second type is called
<br />tht:\\.att:r, where det:p. strong, unobstrucred t10w
<br />occurs. hut With little surface rou~hness (Fl,f.:. SK).
<br />
<br />Figure 58. LOOking downstream from a Ilatwaler reach to a
<br />maJor rapid on [he Colorado River In Grand Canyon,
<br />Arizona, 1970,
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<br />J,'
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<br />.~.....
<br />~ .
<br />" ...,;; ,
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<br />~~
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<br />,'l,-I'
<br />~, , ......
<br />. " .....
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<br />.,:"t:",,!.J,,>:
<br />
<br />Thl' ColorJdo Rlvt'r IS notoflOus for whltewAter,
<br />espeCIally In [he Grand Can}'on, aod the Rio YaquI
<br />tlow>; through similarly constrained n:i1ches through
<br />parts of its course. \X'ider places sepHating can}.ons
<br />tend to hil\'e dlfterent: faunal composiuons, covered
<br />bdow
<br />CanplOs of the Colorado Rin'r sUPPOrt d special
<br />llsh communlry consisting mostly of humphMk chub.
<br />srt'ckleJ dace, hlu('head moumain,sul'ker. ilnd
<br />tlannelmouth sucker. Of tht:se. only the humpback
<br />chub (FI~. 59) IS found in whitewater. where it lives
<br />in deep eddies Jssociated with large boulders,
<br />Indentations In canyon walls. or other protecung
<br />obstructions. This is one of the most bil.lrn' mlnnow
<br />"pecles in the world. with lar~e, strong fins. leathery
<br />skin wlrh det-ply embedded sCJ.les, and a remarkable
<br />hump between the head Jnd dorsal fin. The: last
<br />reflects d powerful Jnd compaCt muscularure
<br />required for movement wltllln ItS habitat and
<br />throu~h rapids serar;Hln,L! one eddying habitat from
<br />JOIlther. Despite years of study. Imle is actually
<br />known of the humpback chub's feeding Jnd
<br />fr-pruductlon. \"\'e know that it lives a relatively long
<br />time. perhaps more than ~O yeHs, and rh;!t It
<br />reproduces In spring/early summer, The fish is rare.
<br />and cl,lsseJ as endangcrr-d, so few h;l'I.e bet'n
<br />s;\(t1fi(ed lor biolo~lcal examinatIOn.
<br />Speckled J;\CC (Fig, ,~I) live along sand anJ gravel
<br />h;!rs of tlat\\'ater tt';lches of the Culorado River.
<br />Fb,nnelmouth suckers O"\c, 60) remalO in deeper
<br />water except when feeding, when they m\we onto
<br />
<br />Figure 59, The largest known popuJallon 01 endangered
<br />humpback chub lives In the towermosl Llltle Colorado River,
<br />Arizona This adult. 36.0 cm tn total length. was
<br />photographed al Willow Beach National Fish HatChery.
<br />
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<br />01107
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