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<br />UU1~tjl
<br />
<br />1646
<br />
<br />C. P. PAUKERT
<br />
<br />sucker and bluehead sucker analyses), diel periods and seasons were combined and a
<br />Kolmogorov-Smirnov test was used (Zar, 1996). A or; level P= 0,10 was set for all tests
<br />(including the power analysis).
<br />
<br />RESULTS
<br />
<br />A total of 272 electro fishing stations and 303 trammel net sets were used from
<br />February to October, 1992 and 1993. Electrofishing collected a total of only 20
<br />humpback chub, 17 flannelmouth suckers and one bluehead sucker 2':200 mm
<br />Lr, whereas trammel netting captured 222 humpback chub, 85 flannelmouth
<br />suckers and 31 bluehead suckers 2':200 mm Lr. Mean CPUE values for electro-
<br />fishing across all years, seasons and diel periods was <0,27, depending on
<br />species (Table I). Mean trammel netting CPUE was also low across all years,
<br />seasons and diel periods, ranging from 0,05 to 0,34, depending on species
<br />(Table I). The variability about the mean CPUE was not related to the dur-
<br />ation of electrofishing (categorized at 0.05 h intervals) for humpback chub
<br />(r=O'IO, n=9, P=0.80), flannelmouth sucker (r=-0'35, n=9, P=0.35) or
<br />bluehead sucker (r = -0'14, n = 9, P = O. 73). Similarly, there were no relation-
<br />ships between variability about the mean CPUE for trammel netting
<br />(categorized in O.lh intervals) for humpback chub (r=-0'33, n=17,
<br />P=0.20), flannelmouth sucker (r=O'OOl, n= 17, P=0.99) or bluehead sucker
<br />(r= -0'37, n= 17, P=0'14).
<br />
<br />CPUE VARIABILITY
<br />
<br />There were no two-or three-way interactions between gear type, season or diel
<br />period in the humpback chub ANCOV A of the CV (P> 0,15). Mean CV was
<br />higher in electrofishing compared to trammel netting (F1,6, P = 0.004) (Table I).
<br />
<br />TABLE!. Catch statistics (mean::l: S.D.) of native fishes collected between rkm 96,6 and
<br />104.7 in the Colorado River, Grand Canyon, Arizona, between February and October,
<br /> 1992 and 1993
<br /> CPUE CV
<br />Species and gear Mean ::I: S.D. Range n Mean ::I: S.D. Range n
<br />Humpback chub
<br />Electrofishing 0.25::1: 1.08 0-8.70 272 338 ::I: 104 210-529 7
<br />Trammel netting 0.34::1:0.72 0-7,13 303 197 ::I: 49 128-283 11
<br />Flannelmouth sucker
<br />Electrofishing 0.26::1: HI 0-8.47 272 383::1: 116 242-566 8
<br />Trammel netting 0.12::1: 0.34 0-2.73 303 268::1: 116 128-469 10
<br />Bluehead sucker
<br />Trammel netting 0.05::1: 0.18 0-1.54 272 347::1: 114 229-575 8
<br />
<br />CPUE, the number of fish ~200 mm Lr collected per hour of electrofishing or trammel netting;
<br />CV, coefficient of variation (100S.D. xl) is an index of variability in CPUE values; n, number of
<br />trammel nets or electrofishing stations for CPUE and number of CV observations for CV (i.e.
<br />season, diel period and year combinations).
<br />
<br />@ 2004 The Fisheries Society of the British Isles, Journal of Fish Biology 2004, 65, 1643-1652
<br />(No claim to original US government works)
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