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 CHANGES, M sis BEHAVIOR, AND
KOKANEE FOOD HABITS IN GRANBY RESERVOIR,
GRAND COUNTY, COLORADO
PATRICK J. MARTINEZ
ABSTRACT
Cyclops bicuspidatus thomasi, Daphnia ag leata mendotae, and
Bosmina longirostris dominated the Granby Reservoir crustacean zoo-
plankton in 1981 and 1982, with peak numbers occurring in late summer.
Daphnia pulex, formerly a preferred food of kokanee salmon
(Oncorhynchus nerka), was extermely rare. Daphnia longiremis, also
present in the past, was absent. Opossum shrimp, (Mysis relicta),
introduced into the reservoir in 1971, have become well established.
M. relicta migrated vertically at night to near the surface into
early summer, but did not enter surface waters during warmer months.
Low dissolved oxygen in deeper water prior to fall overturn appears
to force mysids to shallower areas of the lake. M. relicta consumed
rotifers in the spring but fed heavily on cladoeerans later in the
year. Kokanee fed on chironomids and copepods in spring switching
to D. g. mendotae as it became abundant. M. relicta was included
in the kokanee diet.
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