Acoustic deterrent devices
Alternative leader design
Alternative offal discharge
The physical prodding of non-target species using a pole or other implement to deter them from interacting with a fishing operation (Werner et al. 2006).
Bait manufactured from non-natural substances as a substitute to natural bait that may render it less appealing to non-target animals (Mejuto et al. 2005).
At-call pop-up buoys
A procedure used by purse seine operators that facilitates the escape of trapped dolphins. The backdown occurs after the majority of the net is on board. At this point net retrieval is stopped, the net is tied to the vessel and the engine is put into reverse. This creates a water current that causes the net remaining in the water to form a long channel. The water current also pulls the end of the channel under water providing an area for dolphins to escape (Bratten and Hall 1996).
Devices that toss the bait beyond the turbulence of longline boat propellers that tend to keep bait buoyant longer where it is more prone to seabird predation (Brothers et al. 1999).
A number of devices used to disturb birds from foraging on bait. These include streamers attached to a pole suspended above the area where bait is set or placed in the water, towed buoys, and water jets (http://bycatch.org/articles/shrink-and-defend-comparison-two-streamer-li...).
Buoy lines with reduced breaking strength
Underwater traps or nets linked to a surface buoy by a weak line. To haul the gear, a messenger device would be sent down the weak line along with a stronger hauling line. The messenger device would attach to the hauling line to the bottom gear for retrieving the gear. The premise is that a large whale would easily break free from a weak line suspended in the water column and the stronger line needed for hauling could be located out of harm’s way (Werner et al. 2006).
Devices used for attracting non-target animals away from fishing activity where they might become captured or entangled in gear (ICES 2010).
Decreased soak time
Differently colored ropes
Dummy longline sets
Approaches that include setting longlines in novel patterns (such as in a sinusoidal shape) or using “dummy” sets to mask the presence of a fishing operation (Werner et al. 2006).
Fence or net barriers
Barriers erected in aquaculture and corral-type fishing gear to exclude non-target species. Barrier nets can create a separate bycatch problem based on reports of fatal entanglements that have occurred with California sea lions and humpback whales (Petras, 2003).
High tension rope
Increasing the tension of a fishing rope, such as by simultaneously increasing surface flotation and bottom weight.
Low profile gillnet
Metal oxide/barium sulfate nets
Modified ground gear (mobile)
The setting of fishing gear at night so that seabirds are less likely to see sets. Lights may also be dimmed to enhance the effect (McNamara et al. 1999).
Passive acoustic deterrents
Buoys coated with a material to make them reflect or blend into the natural environment so that they are a less conspicuous signal to sea turtles, which are thought to be attracted to buoys used in fishing operations (Werner et al. 2006).
The application of substances that produce odors to deter non-target species from entering into a fishing area (Southwood et al. 2008).
The placement of fishing gear over the side of a longline vessel rather than the stern. Studies have shown that seabirds avoid going after baited hooks near the vessel hull, and by the time the stern passes them they are deeper in the water than they would be in stern sets (Brothers and Gilman, 2006).
Sub-surface bait setting
Sub-surface sets (gillnets)
Methods that reduce bycatch by eliminating gear sets at the ocean surface. These include devices such as setting chutes that place sets below the ocean surface in longline operations where they are less prone to seabird predation, and setting gillnets below the sea surface to reduce entanglement rates of small cetaceans
Thin twine nets
Time area closures
Time area closures are used as a tool to reduce the incidental capture of bycatch speices (Kimberly et al. 2000).
A digital device that can be programmed to trigger a mechanical arm to move and release gear at a precise pre-set time (hauling ropes and flotation devices) that is being secured at depth until released for hauling.
Trap guards (T-bars, otter guards)
Vessel chasing (hazing)
The use of boats to chase non-target marine animals from a fishing area (Werner et al. 2006).
Vessel noise reductions
The incorporation of rope attachments manufactured to break at a strength lower than that of the rope used, or otherwise reducing the breaking strength of lines used in fishing.