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<br />CALTIi'OHNIA 1"INlI AND (JA~I g
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<br />SPAWNING LOCALE
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<br />'rhe general area where the humpback sl.wkm' was ob~eI'Yed in spawlI;
<br />in'" activities is at the Needles Boat TJHudlllg, located 1Il the n(~rthw('s,
<br />co~ner of JJake l1avasu. Observations were m.acle from the shore of a small
<br />bay south of the landing and its adjacent pomt.
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<br />FIGURE 1. Point south of Needles Boat landing. Photogroph by R. D. Beland, January, 1951.
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<br />The bottom of the bay is silt over sand intermixed with a smatterin~
<br />of boulders and some gravel spotted throughout the shallow areas. NUllH'l-
<br />OIlS depressions over a foot in diameter :vere seen and ap.peared ;o.lw
<br />largemouth black bass (1I:i1'cTopteTuS salmoules) n?sts. AquatIC veget~tlOlI
<br />consists of small clumps of blue-green algae growlllg on the !:lOU l~er~ ~I~\:
<br />bottom, and bullrush (8ciTpUS sp.) pf~tches ~llong the mar.glllal areclS '\.
<br />the head of the bay. 'l'amarisk (l'amanx galhca) adds conSIderable shad
<br />to the littoral zon? in the apex of ~he bay. .. ,. . . . . of
<br />The bottom ad;Jacent to the pomt to the, ~Hlth of ~IJls bay conSIsts ,_
<br />f! three-foot wide silt strip, located about 2;) feet otl'i'>hor~, border?d h.
<br />;:ubble both lakeward and shoreward. No aquatic vegetatIOn was found
<br />in thii'> area and the beach is open.
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<br />SPAWNING OBSERVATIONS
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<br />On March 2, ] 850,W arden 1.1eo ROi'>sier an~l tl~e writ<:J' notpd spawl,'i1il;
<br />humpback suckers and carp (Cyprinus caTplO) m.the l1ttoral area of t I
<br />slllall bay and point south of Needles Boa~ Lan(hng'. Two su:kers, t;nt.;
<br />ripe mal~s exuding milt, were seined. TheIr lengths. w('re2 2~.2 ~n;l ,~\
<br />inches and their weights 4.8 and 5.5 pounds, respec.tJvely.. 1 hey '\,C1 L; :.~
<br />ht'illiant breeding coloration. 'rhe dorsal and h.rteral ~ntcg'un~(,l~t was 1~1,:,,\.
<br />to a point about one inch below the lateralluJe, WIth a bnlhant 01'.11 "
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<br />;-Aii'l~-:;-~h 11leasureInenls are to fork of caudal fin.
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<br />SPAWNINfl OF' THg HUMPfiACK SIJCI{J<;I~
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<br />(olonltion extending ventrad from this point. JJimited time prevented
<br />I'lIl'ther observations on this date.
<br />On March 15th at 3.30 p.m. two gTOUps of suckers were seen working
<br />t heir way along the marginal areas in the apex of the bay south of the
<br />landing approximately 15 feet from shore, in about 18 inches of water.
<br />Itl group one, six fish were noted revolving clockwise at a slow rate in
<br />rOIlI'-foot diameter circles. Suddenly the caudal fins of all fish began to
<br />vibrate violently and one fish jumped clear of the water. It appeared that
<br />fivc of the fish, presumably males, were exerting pressure on one fii'>h,
<br />I'l'esumably a female; three were crowding together on t.he female's right
<br />~icle and two on her left. The two most proximate males were pressing'
<br />"~!l1inst the sides of the female with their heads just behind her hump.
<br />Ensuing violent motion raised bottom silt so that. furth('r ob.servationi'>
<br />1I'(,1'e prohibited. Occasional water agitation was noted dnring' this one
<br />/llId one-half minute period of activity and the Joeation of the fish eould
<br />.asily be determined by the clond of suspended matter raii'>ed from their
<br />\'ioh'nt motions. Following the spawning a('t the fii'>h separated and rnoved
<br />I.way singly, two into deeper wat.er and the other four parallel to the
<br />'lIore.
<br />The second group consisted of t.hree fish lying in a depressed pocket
<br />! possibly a largemouth black bass nest) about t.hree feet from shore in
<br />10 inches of water. Caudal fins of t.he two outer suckers, presumably
<br />males, began vibrating and a column of water about. five inches high by
<br />V'\'('n inehes in diameter was thrown into the air. Again bottom silt.
<br />!,"eluded the actual spawning act. After about one and three-quartel'''
<br />minutes of aetivity, the fish separated. A marine plankton net was towed
<br />Un'ou::!'!l the immediate area, but no spawn was recovered.
<br />Within one-half hour 48 suckers between 20 and 80 inehes long wel'(~
<br />. "llIlted passing through this area. Carp were intermingling with the
<br />,,,,'k..l's and ranged in length between 10 and 15 inches. 1'he1'c was a
<br />.,Iigllt wave action in the bay area, due to an easterly breeze.
<br />!In Mareh 1Gth a strong east wind createcl wave action, preventing'
<br />d..taded observations of fish movements. However, a small sehool of
<br />. !"'k..,,s was located in the same area as of the previous afternoon, but
<br />II" t iglLt grouping was noted. A set was made with a standard sampling
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<br />IIGURE 2.
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<br />Humpback sucker, Xyrauchen texanus (Abbott). Specimen from Colorado River
<br />below Davis Dam. Photograph by W. A. Evan." May 30, 1950.
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