Controlling Gulls At Seafood Plants

Sea Gulls and Seafood Plants

Sea gulls naturally carry illness-causing bacteria Salmonella and Listeria monocytogenes. Keeping sea gulls away from seafood plants helps prevent seafood contamination by these bacteria.

Fishing vessel unloading operations and seafood plant waste disposal equipment often attract sea gulls. Around seafood plants, gulls contaminate the environment with feces. Gull feces can contaminate raw fish and shellfish in open boxes, bins or totes on fishing vessels and loading docks.

Sea Gull Control Techniques

Sea gulls are a persistent problem at landfills, fish hatcheries, outdoor restaurants, and other coastal areas. Attempts to exclude gulls by scaring them are not very productive. Noisemakers, cannons, streamers, rockets, shotguns, and recorded distress calls are expensive and effective for only short periods of time.

Networks of overhead wires keep sea gulls away from buildings and nearby areas. Effective systems consist of wires suspended horizontally in one direction or crisscrossed to form a grid of lines above the area needing protection.

Most networks use monofilament fishing line or stainless steel wire. Monofilament lines range from 40 to 100 pound test, and stainless steel wires range from 0.01 to 0.16 inches in diameter (about 9-32 gauge U.S. standard). You can attach wires to existing buildings or fences, or to poles around the area needing protection.

Advantages of monofilament line are lower cost, no tendency to kink, and ease of installation. Disadvantages include deterioration from exposure to sunlight and possible breakage if gulls fly into the lines. Monofilament fishing line (100 pound test) costs about 8/yard.

Stainless steel wire installs easily and is stronger than monofilament line, but it is more expensive. Stainless steel wire (135 pound test, 0.027 inch diameter) costs about 22/yard.

Researchers testing wire networks cannot explain why gulls are unwilling to fly through wires or lines. Wires appear to startle gulls and may disturb their landing pattern. The few gulls that enter a protected area do so by walking into the area.

Gull exclusion networks use the following materials and wire spacing:

Nesting areas: 40 pound test monofilament line or 0.08 inch diameter wire in parallel lines 4 feet above ground and 2 feet apart.

Fish hatchery raceways: 50 pound test monofilament line in parallel lines 8 inches above water and 16 inches apart.

Outdoor restaurants and pools: 0.01-0.08 inch diameter wire or monofilament line in crisscrossed lines 10-33 feet above ground.

Landfills: 100 pound test monofilament line or 0.016-0.16 inch diameter wire in parallel lines 33-79 feet above ground and 10-100 feet apart.

Control Systems For Seafood Plants

Overhead wire systems will also keep sea gulls from gathering near seafood plants in San Pedro and San Francisco. One plant uses 100 pound test monofilament fishing line in parallel lines spaced 6-12 inches above vents and signs, about 2 feet above the roof, and 10-15 feet apart. Lines connect to 6 foot wooden poles (1 inch x 2 inch) attached to sides of building. Stringing lines about 1 foot out from roof edges prevents gulls from landing on roof edges. The other plant uses a similar system with stainless steel wire.

This work is sponsored in part by NOAA, National Sea Grant College

The author is Robert J. Price, Ph.D., Extension Seafood Technology Specialist Department of Food Science & Technology, University of California, Davis, California 95616-8598.