|
<br />152
<br />
<br />CALIF'ORNIA F'ISH AND GAME
<br />
<br />gill net at 10.J5 a.m. and rnn at 12 m. Four snckers were ?aphJl'('d.
<br />weighed and nleasured, and fin ray COIWtS recorded. All WE're npe mal.,s
<br />and extruded milt when removed from the net. They ranged from 4.8 to
<br />5.6 pounds and 21.2 to 23.1 inches.'
<br />
<br />
<br />FIGURE 3. Four-irloh humpbcak sucker fram the Colorado River below D~vis Dam. The nuchol
<br />hump is absent in this specimen. Phofograph by R. G. Hu/quist, May, 1951.
<br />
<br />The I'>nrface was calm by noon but no spawning groupl'> were S('('II.
<br />~\ few fish were jumping in the center of the bay. 'I'he gill net was nil'
<br />several times during the afternoon in all attempt to capture a gral'i,1
<br />female sucker. li'ive suckers ranging from 4.3 to 5.5 pounds and 19.::' Iii
<br />21.:3 inchel'> were caught, but all were ripc males.
<br />At :3,O:"} p.m. some grouping of the suckers in the apex of the bay \\'11"
<br />noted, but no actual spawning appeared to be taking place. A sligh!
<br />surface ripple made observations somewhat difficult at this time. ']'\\,O
<br />plankton tows were taken with the marine net. One complete tow con.
<br />f'>isted of a 40-foot drag each way. An area over the spawning groIllIds
<br />15 feet by 40 feet was covered. AU depths were samplcd. No spawn was
<br />
<br />3 A fe\v notes \vere taken on the physical appuarance of one of these captured Inale~
<br />5.:1 pounds in weight and 21.5 inches in length. Pronounced breeding tuberch".
<br />approximately three-sixteenths inch in diameter aIl(1 of about the same height, wcr-
<br />noted on the lower nine rays of the caudal fill, a.nd anteriad on approximately tWI'
<br />:.;l,ncl one-half inches of the lateral portions of the cawlal peduncle; the seven rap
<br />of the aIlal fin were also bordered vdth tubercles. The pelvies were sinlilarly covpr,o,l
<br />with tubercles of somewhat smaller size, about one-eighlh inch in diameter. An ".
<br />shaped pattern of tubercles was also noted over the frontal bone.
<br />The m,outh .was typically sub-inferior. The dissection of the bOlle plate above th~
<br />vertebrae, or the predorsal region he tween the occiput and dorsal fin, reveall~d ...
<br />height range of 1.6 inehes, taken just dorsad of lhe posterior edge of the opere!e, II>
<br />1.2 inches at the baRe of the first dorsal ray. I~ewo separations of the plate were ,f(J.Ull,1
<br />between the base of the dorsal spine and the apex of the nuchal hump, which dlvll](,d
<br />the plate into thirds, presumably to per'mit lateral flexibiUly. Below the dorsal fln
<br />a fairly heavy plate, 1.0 inch high, extended over the entire length of the .fish. .
<br />Pin ray counts for this specimen and the other three taken at the same tJrnc ''''en'
<br />constant at D-15, A-7, and C-18.
<br />
<br />SPAWNING OF' THE HUMPBACK SUCKER
<br />
<br />153
<br />
<br />
<br />FIGURE 4. larval humpback sucker taken near Needles Boat Landing, Lake Havasu.
<br />Photograph by R. G. Hu/quist, May, J 951.
<br />
<br />f. eon'I'ed, bnt one larval humpback sucker, 0.4 inch in total length, was
<br />I'/lptmed (identification by Dr. Carl h Hubbs).
<br />(III tile morning of J\Iarch 17th the bay area was wat.ched from the
<br />"I','\'ions loeation, but no suckers were in evidence. An overnight net set
<br />\',"IS run and only seven ripe carp and three bluegill (Lcpornis rnacro-
<br />di/'/(s) were eanght. By 10 a.m. it appeared that no suckers were moving
<br />into this bay area, 1'>0 the observation station was moved to the first
<br />point south of the boat landing, where suckers had been. collected on
<br />~ral'('h 2d. 'l'he water surface was calm and 27 suckers were clearly
<br />\' isible IIIilling about just offshore.
<br />One group, consisting of two males and one female (presumably)
<br />hdween them, was noted moving in a counter-clockwise cirele about.
<br />three feet in diameter. The males appeared to be "herding" the female
<br />wilh their heads and humps, nudging the female in the genital region.
<br />,\ fter about 30 seconds of this circular mo\'Cment aU three lay on tbe
<br />bottom on their ventral surfaces. 'I'he males' caudal fins vibrated rapidly
<br />lJnd appeared to be slapping the female in the genital region. At this
<br />,illle this group was in two fect of water approximately 25 feet from
<br />'he shore, over silt bottom. Silt erupted with this activity and furtber
<br />l,hsf'l'vation waR impaired. 'l'he silt elolld continued in sllspension for
<br />ll...~,.~ 111 i llll /;(~S lwfore the fish were seen to separate and move away. 'l'his
<br />l\l~t lOll was noted between ](J.05 and 10.13 a.m.
<br />A seeond grou p, eOl1sistillg' of three lllales and one female (presurn-
<br />aldy). Will'> observed moving along the silt-bottomed strip betwl'en lO.l:)
<br />aud '\().17 a.m. 'l'he female eseaped to deeper water and no I'>pawlling'
<br />lIr'! i\'ity was lloted. 'rhe f('male appeared li/.!hter in color, being more
<br />""OIl'II I hall blaek on the dorsal side, but of the same size as tht' malE'S.
<br />.\t 10,20 a.III. wave aetion from passing' motor boats dispersed the groups
<br />allll ouly I'>ingle fish were seen.
<br />n.,. 10.45 a.m. only seven suckers were observed in the shallow area,
<br />tl:Clll~h several silt "enlptiollR" were noted 50 feet offshore in 4.5 to 6
<br />reet of water, and apparently some spawning activities were taking
<br />
<br />...
<br />
|