7039

• UCREFRP Catalog Number: 7039
• Author: Pearson, W. D., R. H. Kramer and D. Franklin
• Title: Macroinvertebrates in the Green River Below Flaming Gorge Dam, 1964-65 and 1967
• USFW Year: 1968
• USFW - Doc Type: Utah Academy of Sciences, Arts & Letters
• Copyright Material: YES

160 UTAH ACADEMY PROCEEDINGS, VOL. 45, PART 1, 1968 _
Little Hole
The substrate at Little Hole was composed primarily of com-
pacted rubble with sand and gravel in the interstices. Because
seasonal flooding was reduced, the import of sand and silt from
upstream was reduced and the substrate was relatively stable.
Soft sand-silt bottoms were found in the deeper pools.
Twenty-six groups of organisms were collected at Little Hole
(Table 3), but four groups were dominant: Baetis sp. I, Simuliidae,
Oligochaeta, and Chironomidae. Numbers of Baetis sp. I nymphs
and Simuliidae larvae reached 40,124 and 20,261/m2 on rubble-
gravel substrates, respectively (Table 4). Oligochaetes and Chirono-
midae larvae reached densities of 35,680 and 27,675/m2, respec-
tively, on sand-silt bottoms.
Carr Ranch
The river at Carr Ranch was characterized by a low gradient
and shifting bottom with few silt-free patches of gravel or rubble.
Submerged woody and herbaceous plant debris was abundant,
however, and the clinging and sprawling forms of benthic inverte-
brates inhabited this substrate.
Thirty-six groups of organisms were collected at this station
(Table 3). The four most abundant organisms on debris substrates
were Chironomidae, Oligochaeta, Baetis sp IV, and Baetis sp. I.
Maximum observed densities of these forms were 2,970; 2,518;
1,141; and 624/m2, respectively. On silt-sand substrates, maximum
numbers of chironomids reached 5,650/m2 and oligochaetes reached
1,355/m'-.
Echo Park
This station was located on the Green River 0.8 km above
its confluence with the Yampa. The substrate was largely rubble
and gravel with some silt-sand deposited near shore and inside
bends of the river.
Thirty-seven forms of invertebrates were collected (Table 3).
The four most abundant forms on rubble-gravel substrates were
Baetis sp. I., Hydropsyche, Chironomidae, and Isopcrla, with maxi-
mum densities of 6,510; 1,786; 764; and 441/m2, respectively.
Oligoehactes and chironomids were the most abundant forms on
silt-sand, reaching densities of 430 and 334/m2, respectively.

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