8097

• UCREFRP Catalog Number: 8097
• Author: American Fisheries Society.
• Title: Proceedings of the 18th Annual Meeting, Colorado - Wyoming Chapter, American Fisheries Society.
• USFW Year: 1983.
• USFW - Doc Type: March 2-3, 1983.
• Copyright Material: NO

PRELIMINARY INVESTIGATION OF FEEDING PREFERENCES OF BROWN
TROUT (Salmo trutta): MANNER OF FEEDING AND DIET EFFECTS

GENE RAUCH, TOM MANDIS AND LARRY E. HARRIS

COLORADO DIVISION
FISH RESEARCH
BELL v(JE, CO

OF WILDLIFE
HATCHERY
80512

ABSTRACT

Utilization of "wild" salmonids such as the brown trout
(Salmo trutta) for specific fisheries management goals requires
successful propagation of the entire lot without hatchery selec-
tion of the more easily domesticated individuals. Hatchery
behavior indicated human interferences during feeding could ad-
versely affect growth rates, survival and size uniformity of
the final hatchery product. Therefore, hand-fed lots of brown
trout were compared to lots fed by automatic feeders with surface
feed delivery and automatic feeders with submerged feed delivery
systems. The submerged feed delivery system was designed to
cater to the browns' bottom-feeding tendency. Final growth results
showed those lots fed by automatic feeders with submerged feed
delivery systems had a significantly greater average total length
after 98 days. Little growth benefit could conclusively be
attributed to diet preference or automatic feeding with surface
delivery, perhaps indicating the reluctance of browns to surface
feed even without human interference.

INTRODUCTION

Colorado Division of Wildlife fisheries research and management objec-
tives require artificial propagation of various species and strains of "wild"
salmonids. These wild breeds exhibit inherent characteristics conducive to
specific project goals. Preservation of those inherent characteristics
requires successful propagation of the entire group without selection of the
more easily domesticated fish during their hatchery life.
Brown trout (Salmo trutta) and other "wild" species exhibit similar
hatchery behavior and performance characteristics. They are easily disturbed
by human activity, their growth rates are slow, starvation mortalities are high
at times and the final hatchery product is variable in size.
Earlier studies showed starvation losses could be minimized by training
with BioDiet (Bioproducts Inc., Warrenton, Oregon) (Willis and Flickinger
1980). Size variability of the final hatchery product was theorized to re-
flect variable food acceptance. It was also noticed that human activity
interfered with feeding of a noticeable percentage of these fish. This seem-
ed to be a typical "wild" fish reaction, supporting the philosophy of the
wise fisherman who avoids scaring the fish prior to delivery of the bait.

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