8096

• UCREFRP Catalog Number: 8096
• Author: American Fisheries Society.
• Title: Proceedings of the 19th Annual Meeting, Colorado - Wyoming Chapter, American Fisheries Society.
• USFW Year: 1984.
• USFW - Doc Type: March 7-8, 1984.
• Copyright Material: NO

ZOOPLANKTON FORAGE IN FLAMING GORGE RESERVOIR
ROGER W. SCHNEIDERVIN
and
IdAYNE A. HUBERT
I~lYOMING COOPERATIVE FISHERY AND WILDLIFE RESEARCH UNIT
UNIVERSITY OF WYOMING
LARAMIE, WYOMING 82071
ABSTRACT
The rainbow trout, Salmo gairdneri, fishery in Flaming Gorge
Reservoir has declined since the mid-1960's, despite an intensive
fingerling stocking program. One hypothesis for the decline is a
shortage of suitable-size zooplankton forage due to competition
from other zooplanktophagic fishes. This report describes the
abundance and size-distribution of zooplankton found in 1983 and
compares these results to data from 1965 and 1966. These preliminary
findings are used to evaluate the possible influence of competition
for zooplankton forage on rainbow trout fingerling survival in the
reservoir.
INTRODUCTION
Flaming Gorge Reservoir was created in November, 1962, by impoundment
of the-Green River behind Flaming Gorge Dam. The reservoir is located in
southwest Wyoming and northeast Utah and when filled to capacity is 145 km
(91 mi.) long, impounds 17,000 ha (42,000 ac.) of water and has a maximum
depth of 134 m (440 ft.). Since impoundment the reservoir has been managed,
as a rainbow trout fishery with 56 million rainbow trout, Salmo gairdneri,
(approximately 3 million per year) planted between 1962 and 1981 (Schmidt et.
gal.. 1981). Despite the intensive stocking program, the fishery has steadily
declined from a 1965 peak, with overall catch rates dropping from 1.3 fish
per fisherman-hour in 1965 to 0.15 in 1979 (Schmidt et al. 1979, Wiley
1978). One .hypothesis for this decline suggests that changes in zooplankton
abundance or size may have occurred in Flaming Gorge Reservoir resulting in
a lack of suitable-sized zooplankton as forage for rainbow trout. In 1965
and 1966 a quantitative description of zooplankton present in Flaming Gorge
Reservoir was conducted by Varlet' (1967). Our paper reports 1983 zoo-
plankton size and abundance and compares current stocks with those of 1965
and 1966.
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