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<br />11
<br />
<br />Tab 1 E? 4.
<br />
<br />Volumes of water sampled (m3) by drift-nets, Yampa River,
<br />1985.
<br />
<br />-_...._._-..........._~..._........_.,,,.......m...._................__._.~_......_.".._m.__...__._......~...._............................,...............-...........................................
<br />..._..m"..............._.........."'.._............._.."..........__H._.._..."._.......____...."..._.........._....._.h........."......................_....,...........N..__....
<br />
<br />Near-shore
<br />
<br />Middle
<br />
<br />Main chctnnel
<br />
<br />......-.......,,-............... ....-.....................,.,........ ,......... ~.-.M....-...-......_...____..........."..._,............n..<__...._..-....,..._........._....... ....
<br /> ..............................._.._......_.......... '........__.._...._....._......................_......'h.._..._............_.._._......__. .....n'_.._'...,....,."..._~.._.._.......~._....
<br /> .._,....__......_._.
<br />
<br />Total
<br />volume
<br />(m~)
<br />
<br />42, 158
<br />
<br />46,530
<br />
<br />44,551
<br />
<br />Weekly
<br />volume
<br />(m~)
<br />
<br />5,724
<br />10,476
<br />8,408
<br />4 , 590 .
<br />2,484
<br />5, 184
<br />5,292
<br />
<br />7;560
<br />11;772
<br />9,702
<br />4,536
<br />2,484
<br />5,400
<br />5,076
<br />
<br />7, 129
<br />9,612
<br />10,044
<br />4,428
<br />2,430
<br />5,724
<br />5, 184
<br />
<br />Dai 1 Y vol.
<br />range
<br />mean
<br />
<br />972-3,888
<br />2,480
<br />
<br />972-4:;536
<br />2,737
<br />
<br />972-3,781.
<br />2,620
<br />
<br />Sample vol.
<br />range
<br />mean
<br />
<br />162-1 ,62C~
<br />
<br />108-1 ,.~20
<br />684
<br />
<br />108-1,296
<br />.~55
<br />
<br />620
<br />
<br />ranging up to 108 individuals/1000 m3, and averaging 13.7/1000 m~ in
<br />the dawn samples. From diel adundance ratios r-eported in Haynes et al.
<br />(1985), no significant differences were e:<hibited between time periods at
<br />the Box Elder site in 1983 and 1984. However-, a look at the actual diel
<br />density data suggests that a pattern similar to that exhibited for 1985
<br />was also evident in 1984, especially during the period of peak drift
<br />densities. The peak diel densities in 1984 were 13.9, 3.1, 3.1, and 1.1
<br />larvae/1000 m3 for the dawn, noon, dusk and midnight periods,
<br />respectively. The average drift density for Colorado squawfish during the
<br />dawn period at Box Elder in 1984 was 2.5 larvae/l000 m3. In 1983 at Box
<br />Elder, though, overall and peak drift densities of Colorado squawfish
<br />larvae indicated a greater abundance during the midnight period. Peak
<br />densities reached 15.8, 14.9, 8.6, and 26.0 larvae/l000 m~, and averaged
<br />2.6, 2.8, 1.8, and 4.2 larvae/1000 m3 during the dawn, noon, dusk, and
<br />midnight period, r-espectively, in 1983. Diel abundance ratios for
<br />Colorado squawfish larvae at the Stateline drift-net site used in 1984 on
<br />the Green River indicated significantly greater densities of Colorado
<br />squawfish larvae during the dawn periOd, but was based on a sample of only
<br />27 larvae and a peak dawn drift density of 1.1 larvae/l000 m3 (Haynes et
<br />a 1. 1. 985) .
<br />Of the other three species, only channel catfish demonstrated a
<br />similar peak in drift densities associated with the dawn period in 1985.
<br />Larval catfish densities ranged up to 202 individuals per 1000m~, and
<br />averaged 68.2/1000m3 for the dawn periad. As a mare abundant species
<br />relative to Colorado squawfish, larval catfish were also much more
<br />
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