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<br />001503
<br />
<br />1648
<br />
<br />C. P. PAUKERT
<br />
<br /> 16000 3000
<br /> 2500
<br /> 12000
<br /> 2000
<br /> 8000 1500
<br /> 1000
<br /> 4000 --~-.
<br /> .----.----- 500 ...-~_..
<br /> 0 0 .----.----
<br /> 12000 (c) 2000 (d)
<br /> 10000 1500
<br />Q)
<br />-~ 8000
<br />'"
<br />~ 6000 1000
<br />~ ~. ~.
<br />4000 -- ...,.--,,,-
<br /> ...'
<br />en -...-...-- 500 . --'
<br /> 2000 .,-- .---- '
<br /> 0 0
<br /> 10000 (e) 1500 (0
<br /> ,.
<br /> 8000 ,. ,
<br /> , ,;
<br /> ,; 1000 ,
<br /> " ,
<br /> 6000 , -
<br /> ..~ , ....
<br /> .-
<br /> 4000 .' ,..
<br /> ,.. 500 .. ..-
<br /> .. ..-
<br /> 2000
<br /> 0 0
<br /> 0,6 0,7 0,8 0,9 0,6 0-7 0-8 0,9
<br /> Statistical power
<br />
<br />
<br />
<br />
<br />FIG. 1. Sample size needed to detect (a), (c), (e) 10 or (b), (d), (f) 25% change in CPUE for (a), (b)
<br />humpback chub and (c), (d) flannelmouth sucker collected with electrofishing (-.) and trammel
<br />netting (--e--), and (e), (f) bluehead suckers with trammel nets (--e--) at four levels of power.
<br />
<br />SIZE STRUCTURE
<br />
<br />The proportion of humpback chub ~200 mm Lr collected by electrofishing
<br />ranged from 1 (daytime during the autumn) to 6% (night-time during the
<br />spring), whereas the proportion of humpback chub ~200 mm Lr collected by
<br />trammel netting ranged from 89 (night-time during the spring) to 97% (night-
<br />time during the summer). The proportion of fish ~200mm Lr differed by gear
<br />ty~e (X2, d.f. = I, P < 0'001) but not season (X2, d.f. = 2, P=0.40) or diel period
<br />(X, d.f. = l, P = 0,11). A higher proportion of large humpback chub were
<br />collected with trammel nets compared to electrofishing (Fig. 2).
<br />In only one instance (night-time during the autumn) there were at least 10
<br />tlannelmouth sucker collected by electro fishing (n = 11) so analysis of size
<br />structure could not be conducted for different diel periods and seasons. The
<br />proportion of flannelmouth suckers ~200 mm Lr collected by electrofishing
<br />(49%), however, was lower than from trammel netting (100%). There was a
<br />higher proportion of smaller fish collected by electrofishing compared to tram-
<br />mel netting (KSa = 2,85, P < 0.001) (Fig. 2). For bluehead suckers, only trammel
<br />netting in the spring during the daytime collected at least 10 fish (n = 13). Only
<br />
<br /><<:l 2004 The Fisheries Society of the British Isles, Journal of Fish Biology 2004,65, 1643--1652
<br />(No claim to original US government works)
<br />
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