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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
\
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<br />12 <br /> <br />ture. A total of 100 larvae placed directly into <br />another aquarium served as controls. Survival was <br />99% in the controls and 89 to 93% in the test <br />groups (Table 2). Our inconclusive subjective evalu- <br />ation was that the modest losses were due as much <br />to trauma from impingement on the recapture net <br />as to dam passage. <br /> <br />Age and Growth <br /> <br />The reliability of scales, the most widely used <br />structure for determining the age of freshwater <br />fishes, has been questioned for catostomids because <br />ages of old fish are often underestimated (Dence <br />1948; Coots 1965; Geen et al. 1966; Coble 1967; <br />Beamish 1973; McAda and Wydoski 1980; Minckley <br />1983). Strong evidence of age underestimation has <br />also been reported in the cui-ui; fish recaptured up <br />to 7 years after they were tagged with Carlin tags <br />showed no increase in the number of scale annuli <br />(Gary Sonnevil, U.S. Fish and Wildlife Service, Great <br />Basin Complex, Reno, Nevada, personal <br />communication). <br />In contrast, the use of opercle bones to age cui-ui <br />proved successful. We used opercle bones taken <br />from dead cui-ui collected along the fish way , in the <br />FPB, or at the Pyramid Lake Paiute Indian Cui-ui <br />Hatchery; from fish sacrificed in food and fecundity <br />studies; and from museum specimens. Fresh oper- <br />cles collected in 1982-84 were boiled to separate <br />tissue from bone. In preserved (museum) specimens, <br />the tissue was separated by scraping it off the oper- <br />cles with a scalpel. Cui-ui were aged by counting <br />annuli from the centrum out to the edge (Fig, 9). <br />In older fish, the fenestrated bone associated with <br />the expansion of the opercle-hyomandibular socket <br />was ground to expose the first one to three annuli. <br /> <br />Opercles were selected over fin rays, otoliths, and <br />vertebrae because they were easy to interpret and <br />could be conveniently processed for reading. Annuli <br />were determined according to the criteria of Cas- <br />selman (1973) for cleithra of northern pike (Esox <br />lucius), Relatively transparent regions of the oper- <br />cle were accepted as being areas of the greatest <br />calcium concentration, indicative of slow or winter <br />growth, and the more opaque regions were <br />accepted as indicating a greater concentration of <br />proteinaceous material and accelerated growth. The <br />outer limit of each anulus was generally represented <br />by a narrow transparent zone, In cui-ui more than <br />about 20 years old the transparent zone was greatly <br />reduced. An annulus was defined as the region <br />where the outer edge of a transparent zone abutted <br />an inner edge of an opaque zone, Although some <br />young adults collected late in the spawning run had <br />already formed the annulus and part of the opaque <br />zone, most mature fish appeared to form the annu- <br />lus after the spawning season, In assigning ages, we <br />credited these fish with a "virtual" annulus at the <br />outer edge of the opercle until the annulus was <br />formed. <br />Beamish and McFarlane (1983) stressed the impor- <br />tance of validating annuli in older fish to verify that <br />they were indeed being formed. Our technique of <br />aging was validated by monitoring individual year <br />classes through time. The 355 opercle specimens <br />collected in 1956-84 included fish 1 to 41 years old, <br />but only 11 year classes were represented in this <br />broad span, Once these year classes were tentatively <br />identified, the addition of annuli could be followed <br />in succeeding years. For example, because the 1969 <br />year class was dominant in the population in <br />1982-1984, opercular annuli could be easily veri- <br />fied by monitoring this group each year. In the first <br /> <br />Table 2. Survival of cui-ui larvae recaptured and held in Truckee River water for 48 h after passage <br />over Marble Bluff Dam. Survival in control fish similarly held was 99 %. <br /> <br /> Number of larvae Survival <br />Date River flow Released Recaptured 48 h after <br />Oune 1984) (m3/s) above dam below dam recapture (%) <br />4 65 3.000 70 89 <br />13 45 2,300 59 88 <br />22 23 5,000 140 93 <br />
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