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7/14/2009 5:02:31 PM
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UCREFRP
UCREFRP Catalog Number
7918
Author
Scoppettone, G. G., M. Coleman and G. A. Wedemeyer.
Title
Life History and Status of the Endangered Cui-ui of Pyramid Lake, Nevada.
USFW Year
1986.
USFW - Doc Type
\
Copyright Material
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<br />More than 98 % of the downstream migrants cap- <br />tured in the plankton nets were swim-up larvae, <br />10.5-12.5 mm long, with well-developed yolk sacs. <br />The rest, which were 13.0-30.0 mm long and typi- <br />cally captured later in the season, had obviously <br />remained in the river for various periods after swim- <br />up. We believe that our samples reflected typical <br />outmigrations in 2 of the 3 years of fishing: In 1982, <br />emigration began on 29 May, peaked on 15 June, <br />and ended on 22 July; and in 1984 the emigration <br />dates were 10 May, 3 June, and 2 July (Fig. 7). The <br />peak emigration followed peak adult migration by <br />26 days in 1982 and 29 days in 1984; adult migra- <br />tions peaked on 20 May in 1982 and 3 May in 1984 <br />(Figs. 4 and 7). The rather brief period between peak <br />migration of adults and that of larvae is consistent <br />with our observation that radio-tagged adults <br />spawned soon after they were released from the <br />FPB. <br />A comparison of catches in the plankton nets in <br />1982 and 1983-years in which we monitored <br />emigration at both the upper and lower ends of the <br />fishway-suggests that our catches in 1983 may not <br />have been representative. Whereas the numbers of <br />larvae captured in the upstream and downstream <br />ends were identical in 1982 (indicating that the <br />larvae had been produced in the river upstream) <br />fewer larvae were taken in the upstream nets than <br />in the downstream nets in 1983 (indicating that <br />cui-ui spawned in the fishway itself-even though <br />it afforded poor spawning habitat and generally <br />yielded few larvae-and that recruitment from the <br /> <br />11 <br /> <br />river was low). Consequently we are not confident <br />that the 1983 emigration pattern (Fig. 7) clearly <br />reflects the behavior of river emigrants in that year. <br /> <br />Daily Pattern <br /> <br />The plankton netting station was operated over <br />one or more 24-h periods in each of the 3 years of <br />river study. Effort was most intensive in 1984, when <br />we conducted four 24-h studies at I-week <br />intervals-one before, two during and one after <br />peak emigration-at a station below MB dam. <br />Larval cui-ui emigrated downstream almost exclu- <br />sively at night in 1984-primarily between 2200 <br />and 0300 h (Fig. 8). Results in 1982 and 1983 (not <br />shown) were essentially identical. Nocturnal emigra- <br />tion is not unique to larval cui-ui, but has also been <br />noted in other catostomids (Geen et al. 1966; <br />Clifford 1972), as well as in other species (e.g., <br />Northcote 1969). <br /> <br />Effect of Marble Bluff Dam <br /> <br />Larval mortality due to trauma from passage over <br />MB dam was investigated in 1984. Three groups of <br />hatchery-reared larvae were released at the top of <br />the dam, and representative samples were recap- <br />tured in plankton nets immediately below it. The <br />larvae were then held in an aquarium supplied with <br />Truckee River water. The aquarium was aerated and <br />partly immersed in river water to control tempera- <br /> <br /> 600 <br /> - May 22-23 !\ <br /> '-.-. May 30-31 I \ <br /> 500 ---- June 7-8 I \ <br /> I \ <br /><D .......... June 14-15 I \.-.- <br />t1l <br />c: 400 I --- . <br /> \ <br />..!!! , \ <br />;> I /\ \ <br />':; / \ <br />U 300 I / \ \ <br /> -" \ <br />"6 i I -- \ \ <br />Q; . , \ <br />.0 I, \ \ <br />E 200 i' \ \ <br />:J . , \ <br />Z I' \ \ <br /> ., \ <br /> JI \ \ <br /> .... <br /> 100 ./ .... \ <br /> It , <br /> I .... ....--.l, <br /> ..... . <br /> -:-f::..... ..... .~ <br /> 0 '- .~--. "t-.~................. <br /> 1200 1800 2400 0600 <br /> Hours <br /> <br />Fig. 8. Die! emigration patterns of <br />larval cui-ui monitored weekly in <br />1984. <br />
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