7268

• UCREFRP Catalog Number: 7268
• Author: Persons, W. R. and R. V. Bulkley
• Title: Feeding Activity and Spawning Time of Striped Bass in the Colorado River Inlet, Lake Powell, Utah
• USFW Year: 1982
• USFW - Doc Type: North American Journal of Fisheries Management
• Copyright Material: YES

406
PERSONS AND BULKLEY
Table 1. Stage of maturity of adult striped bass captured at Gypsum Canyon in 1980 and 1981

Sex and stage
of gonads
Number
captured 1980
Percent
of total 1981,
Number
captured
Percent
of total Totals
Number
captured
Percent
of total
Male
Immature 9 4.5 3 1.5 12 3.0
Maturing 6 3.0 2 1.0 8 2.0
Ripe 121" 61.1 89 43.4 210 52.1
Spent 1 0.5 51 24.9 52 12.9
Totals 137 69.2 145 70.7 282 70.0
Female
Immature 6 3.0 8 3.9 14 3.5
Maturing 15 7.6 4 2.0 19 4.7
Ripe 25 12.6 8 3.9 33 8.2
Spent 15 7.6 40 19.5 55 13.6
Totals 61 30.8 60 29.3 121 30.0
Grand totals 198 205 403
Does not include 23 fish of undetermined sex and stage of maturity that were released
'Includes some partly spent fish.
females and outnumber females there at any given
time (Raney 1952). More than twice as many
males as females were captured during the two
study years at the Gypsum Canyon sampling site
(Table 1). During 1980, the surface-water tem-
perature was 13 C on April 26 when sampling
began. Sexually mature males were captured as
soon as sampling was begun, but sexually mature
females were not taken until May 20 when the
water temperature was 16 C. Spent females were
first captured on June 11 and were collected
thereafter during the rest of the 1980 sampling
period. Spent males were captured late in the
sampling period.
Whereas the early part of the spawning run
was sampled during 1980, the latter part of the
run was sampled in 1981. Evidently striped bass
already had begun spawning when sampling was
started on May 26, 1981 when the water tem-
perature was 16 C. The first fish captured was a
spent female, and spent fish were captured
throughout the rest of the sampling period. The
proportion of spent fish increased and the pro-
portion of sexually mature fish decreased in the
catch as the sampling period progressed. More
than 40% of the striped bass captured during
1981 were spent, but less than 10% of those caught
in 1980 were spent. The greater percentage of
Table 2. Stomach contents of adult striped bass, at different stages of maturity, captured at Gypsum
Canyon, 1980 and 1981. (Percentages are in parentheses).

Sex and stage
of gonads

Number Number
with empty
stomachs Number
with empty
intestines

Food Number of stomachs containing
Threadfin Red Unidentified
shad shiner fish remains Crayfish
Male
Immature 12 7(58) 4(33) 5(42) 4(33) 1(8)
Maturing 7 7(100) 5(71)
Ripe 147 113(77) 104(71) 34(23) 31(21) 2(l) 1 (1)
Spent 50 35(70) 28(56) 15(30) 15(30)
Totals 216 162(75) 141(65) 54(25) 50(23) 3 (1) 1 (0.5)
Female
Immature 14 8(57) 6(43) 6(43) 6(43)
Maturing 15 6(40) 7(47) 9(60) 9(60)
Ripe 30 19(63) 13(43) It (37) 11(37) 1(3)
Spent 46 29(63) 22(48) 1707) 1503) 1(21) 1 (2)
Totals 105 62(59) 48(46) 43(41) 41(39) l (1) 1 (1)
Grand totals 321 224(70) 189(59) 9700) 91(28) 4(l) 2(l) 1 (0.3)

spent fish c
water tem
(Fig. 2, Ta
Location o
The ava
Powell stri
in the lows
upper mix
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and spent
yon area. 7
of ripe ma;
that the si
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prevente,
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Food '.
Most stri
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before reac
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Trent and
42% of the
fish, 25% o
33% of thos
321 stomac
were empr
threadfin sk
shiners (N(
remains e
Empty
sons other 1
(Merriman
and regurgi
netted fish. i
stomach anc
would diges
less of speci(
ted fish is a
in lower esti
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age of stoma
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not evacuate