Fishermen using Cornwall’s offshore waters have managed to test the floating visual deterrent aimed at keeping diving birds away from fishing equipment.
This technology was developed by marine researchers and consists of floating “Looming Eye Buoys” with a rotating head creating an animated eye effect to deter seabirds.
Field trials estimated that it is capable of reducing the risk of guillemot and razorbill bycatch by 59 percent.
It is an inexpensive way for fishermen to help preserve marine biodiversity of the region.
How to intercept diving seabirds along coastal gillnet zones
Cornish fishermen deploy gillnets in shallow coastal waters in which the birds like guillemots and razorbills dive down as much as 100 feet looking for sand eels.
Underwater, the monofilament mesh is almost invisible to the eyes, ensnaring the birds while they try to rise back up after a hunting dive.
Researchers attached floating buoys with rotating visual scarecrows along the net lines to deter diving birds.
Birds, flying overhead, are scared by the eyes at a distance and take a new direction of flight without diving into the nets.
Monitoring bycatch reduction in large commercial fishing waters
Researchers fitted the bird scare technology on commercial fishing vessels in Cornwall over a two-year trial, noting that coastal seabird bycatch in the region occurs predominantly during the winter months.
Scientists made measurements of the catches in the nets during more than 50 runs of commercial fishing to compare such nets with protection against the control nets.
It was estimated that using this device resulted in a 59 percent reduction in the risk of seabird bycatch.
The device was tested during a two-year trial involving 10 fishing vessels to assess the effectiveness of the above-water rotating visual deterrent.
How to solve the problem of line tangles and improve durability of marine hardware
The effect of the rough waves on the oceans is the tangling of floating cable lines that connect to gillnets laid on the seabed.
Mooring lines become entangled in the nets while dragging the buoys below, causing the spinning discs to be obscured and possibly resulting in damage to the gillnets through mechanical hauling.
Swivel tethers and counterweights were included in the design to ensure that the lines do not get tangled with monofilament gillnets.
Salt spray and marine crust will prevent rotation of the spindles after a few weeks without special water-repellent lubricants.
Durable marine plastics kept manufacturing costs low, allowing independent vessel operators to equip nets without external subsidies.
Prevention of mechanical entanglement ensures that the fishers are not compelled to discard the scarecrows owing to the tough conditions prevalent during commercial fishing activities.
Visual scarecrows deterrents vs. acoustic pingers deterrents comparison: Which one is better?
Acoustic pingers were used in gillnet fisheries to deter harbor porpoises and diving birds from entering the net meshes.
Diving seabirds do not have a good sense of underwater hearing. This is why the acoustic pingers fail to work effectively against guillemots and razorbills.
The acoustic pingers are also prone to habituation, as marine animals tend to get used to the sounds made by them within a matter of weeks underwater.
Visual scarecrows deter the birds through the instinct of fleeing from predators.
Substituting surface visual signals for underwater noise pollution protects birds while reducing acoustic stress across coastal ecosystems.
The use of optical warnings provides specific species protection without affecting any other species in the area along the sea floor.
The environmental limitations on optical surface warning buoys
Visually deterrent devices will work to deter surface approaches, but they have no effect at all when there is heavy fog on the ocean and coastal haze, especially at night.
Guillemots often forage during early twilight hours when low light levels prevent reflective eye disks from casting visible glare, according to the University of Exeter.
Visual buoys cannot eliminate all bycatch because panicked birds flying low over ocean waves still collide with net floats.
Testing continues on low-power light-emitting diodes to maintain visual deterrence during dark winter fishing operations.
Combining optical scarecrows with modified net setting times provides the greatest safeguard for coastal seabird populations.
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