7605

• UCREFRP Catalog Number: 7605
• Author: Schaeffer, L.
• Title: Avian Predators at ODFW Hatcheries
• USFW Year: 1992.
• USFW - Doc Type: Their Identification and Control.
• Copyright Material: YES

INTRODUCTION

Most piscivorous (fish eating) birds are opportunistic
feeders and take whatever food is most easily accessible.
Artificial rearing areas, heavily stocked during certain times of
the year, attract these birds. Hatchery fish, having spent all
their lives in a protected environs, tend to be naive about
predators. Although the fish are wary by nature, they may not
respond appropriately to a predator attack. When fish are
crowded in hatcheries they are easier for birds to catch than are
fish in a natural setting.

Among the factors that affect the predator-prey relationship
between fish eating birds and hatchery-reared fish are the size
of the fish and the hatchery location. American dippers (Cinclus
mexicanus) and belted kingfishers (Ceryle alcyon) are attracted
to fry and fingerlings stocked in ponds. As the fish grow they
attract herons (Ardea herodias and Butorides striatus), osprey
(pandion haliaetus) and cormorants (Phalacrocorax auritus).

Hatcheries located near nesting sites, flyways, or estuaries
routinely have severe avian predator problems. Coastal
hatcheries in general have greater problems than inland
hatcheries with fish lost to avian predators. Locations with
naturally occurring populations of fish attract fish eating
birds, and fish hatcheries are usually constructed near natural
concentrations of fish.

Oregon Department of Fish and wildlife (ODFW) undertook a
project to identify avian predators, and to examine efficient
means to prevent predation losses at fish rearing facilities.
The project estimated numbers and types of avian predators and
identified predation prevention activities during and after fish
releases. Predator prevention activities at the hatcheries fell
into two categories: use of frightening devices, and construction
of physical barriers.

Some level of fish loss as a result of predation is expected
when fish are reared in culture. Determining exactly how many
fish are lost is difficult. For this report, hatchery managers
estimated predation losses' along with costs to correct existing
problem areas or eliminate predator losses entirely.

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