WSP12650

• File Number: 8220.101.10.A
• Description: Colorado River - Water Projects - Glen Canyon Dam-Lake Powell - Glen Canyon AMWG
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 9/14/2004
• Author: C P Paukert
• Title: Comparison of Electrofishing and Trammel Netting Variability for Sampling Native Fishes - Journal of Fish Biology - 2004 - 65 - 1643-1652 - 09-14-04
• Water Supply Pro - Doc Type: Report/Study

UUI~Hj~

SAMPLING VARIABILITY FOR RARE RIVERINE FISHES

1649

20 (a)
18
16
14
12
10
8
6
4
2
0
16 (b)
't:l 14
Q)
13 12
.9l 10
'0
'" 8
~
Q) 6
'"
~ 4
p.. 2
0
30 (c)
25
20
15
10
5
0
0 100 200 300 400 500 600
LT (mm)

FIG. 2. Total length distributions of (a) humpback chub, (b) tlannelmouth sucker and (c) bluehead sucker
collected by trammel netting (D) and electrofishing (.) in February to October, 1992 and 1993,
from rkm 96,6 to 104'7, the Colorado River, Grand Canyon. (a) n=636 for electrofishing and 234
for trammel netting, (b) n = 35 for electrofishing and 85 for trammel netting and (c) n = 7 for
electrofishing and 31 for trammel netting.

one of seven bluehead suckers collected by electrofishing was ;::::200 mm Lr,
whereas only one of 31 bluehead sucker collected by trammel netting was
<200 mm Lr. Electrofishing collected a higher proportion of smaller fish
compared to trammel netting (KSa = 1,97, P < 0.001) (Fig. 2).

DISCUSSION

Trammel netting for native fishes in the Grand Canyon produced lower
variability in CPUE and a higher proportion of larger fishes than electro fishing,
regardless of season and diel period. Low catches of all three native fish species,
however, led to high variability in both trammel nets and electro fishing, even
though sampling was conducted in areas believed to be occupied by native fishes
(Hoffnagle et at., 1999). Both gears are commonly used to collect native Colorado
River fishes (Keading & Zimmerman, 1983; McAda & Wydoski, 1985; Chart &
Bergersen, 1992; Valdez & Ryel, 1995; McKinney et at., 1999) and both have been

(Q 2004 The Fisheries Society of the British Isles, Journal of Fish Biology 2004,65, 1643-1652
(No claim to original US government works)