Acoustic pingers/alarms – Underwater sound-emitting devices attached along fishing nets. Maximum sound level is approximately 175 dB re 1 _Pa @ 1m or less.
Acoustic harassment devices – Devices that emit sounds of such high intensity that they cause pain or fear in certain underwater species. The minimum sound level is approximately 200 dB re 1 _Pa @ 1m. AHDs are used primarily in aquaculture operations.
Passive acoustic deterrents - Objects such as rubber tubes, thick polyester rope, and chains attached to fishing nets to alert a marine animal to their presence.
Echolocation disruptors – Sounds produced to disrupt the normal echolocation abilities of cetaceans.
Vessel noise reductions – Structural or operational changes to fishing vessels that would decrease the intensity or signature of their sound output, potentially decreasing the degree to which they attract animals that associate these vessels with a feeding opportunity.
Glow rope - Glow rope consists of polypropylene blended with a phosphor that glows a bright yellow-green underwater, in wavelengths large cetaceans can see. It glows for 48 hours after activation at an intensity a human can see readily at 20 yards (18 m). The rope is recharged by a five-minute exposure on a sunny day, 10 minutes on a cloudy day, or exposure to a fluorescent light for one minute.
Excluder devices - A grid of metal bars placed within the neck of a trawl with an opening for escape at either the top or bottom. Large animals that strike the bar exit through the opening, while small animals such as shrimp pass through the bars and are captured in the net. Examples of excluder devices are the Nordmore grid, the Turtle Excluder Device (TED), and the Sea Lion Excluder Device (SLED).
Long gangions - Longer gangions (leader lines attached to the main floating line of a longline) are used to reduce seaturtle bycatch by improving their chance of reaching the water’s surface to breathe if hooked. In the Atlantic, NOAA prohibits longliners from setting gangions within two gangion lengths of the floatline.
Circle hooks – A modification to J-hooks in which the hook is rounder. The design was made for reducing the number of sea turtles hooked in longlines as well as improving their survival once hooked.
Break-away lines – Rope designed to breaks at strengths substantially lower than usual for hauling ropes. The intent is for ropes to function normally for fishing but break under the force exerted by the pull of an entangled large whale.
Time tension line cutter – A link connecting the bottom gear and vertical line in a pot fishery that would break under any pressure sustained longer than the time it takes for a fisher to haul in the gear. The line cutter can be reset before it is redeployed.
Stiff rope – An innovative kind of rope that is stiff in the water column but loose on the deck of a boat. Various prototypes are in research and development. The theory behind these ropes is that their rigidity will prevent them from entangling large whales while fishers will find them at least as practical as regular rope.
Buoy line messenger system – Underwater traps or nets are linked to a surface buoy by a weak line. To haul the gear, a messenger device is sent down the weak line along with a stronger hauling line. The messenger device attaches the hauling line to the bottom gear for retrieving the gear.
Lipid soluble rope – A rope that would dissolve once embedded in the blubber of a large whale.
Medina Panel - A panel of fine mesh attached to the part of the purse seine farthest from the boat when the net is “pursed.” The fine mesh prevents dolphins from becoming snared and creates an escape ramp to the top of the net.
Bird-scaring devices – A number of devices are 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.
Bait casting machines – Devices that toss the bait beyond the turbulence of boat propellers that tend to keep bait buoyant longer.
Dyed bait – Bait dyed a color (blue) to reduce its visibility to non-target species such as seabirds.
Noxious bait – Bait that is treated with compounds intended to make it unpalatable to non-target species.
Thawed bait – Frozen bait is thawed before it is set in the water to increase the rate at which it sinks. The sinking rate can also be increased by puncturing the swim bladder of fish bait.
Baiting techniques – Applying alternative methods of securing bait to a hook or other fishing gear.
Soak time – The length of time that fishing gear is submerged between hauls.
Deep-water sets – Baited hooks in longline fisheries are set in deeper waters to avoid principle feeding zones of sea turtles.
Sinking ground line – A new generation of sinking rope designed to lie along the bottom between traps – advanced versions are abrasion resistant and do not retain grit.
Metal oxide nets - Nylon nets infused with barium sulfate or other metal compounds that have acoustical detection features for reducing small cetacean bycatch. They are stiffer than conventional nets that may contribute to reducing entanglements.
Galvanic releases – Links on haul ropes designed to eventually dissolve, thereby releasing any line that may have entangled an animal. Galvanic releases have also been proposed to reduce the number of vertical lines in the water by securing hauling lines in a coil at the ocean floor until the release dissolves, thereby releasing a buoy that brings the hauling line to the surface.
Acoustic releases – Devices that use an acoustic trigger for releasing a buoy attached to submerged pots that then floats to the surface for retrieval.
Breakaway float releases – Links on rope that are designed to break under the pull exerted by a large whale or another large, non-target animal.
Underwater sets – Devices such as setting chutes that increase the rate at which bait in longline operations gets below the ocean surface.
Line shooter – A device used on longline boats to increase the speed at which baited line gets below the water’s surface where seabird predation mainly occurs.
Raised footropes – The lower edge of a trawl net’s “mouth” is raised high enough in the water column to prevent it from dragging across the benthos.
White twine on gill net tops – White twine on the upper part of a gill net to make it more visible to diving seabirds.
Artificial bait – Bait manufactured from non-natural substances as a substitute to natural bait.
Sea turtle-friendly bridles – A bridle design used in trap fishing for minimizing sea turtle bycatch.
Remote attractor devices – Devices used for attracting non-target animals away from fishing activity where they might become captured or entangled in gear.
Fence or net barriers – Supplemental barriers erected in corral-type fishing methods that reduce the trapping of non-target species.
Pyrotechnics – The use of loud explosive devices, including gunshots, to scare nontarget species such as seals away from a fishing operation. (Water compression caused by gunfire is probably more important than the sound of the gun firing, sand as such can also be considered a tactile deterrent).
Predator sounds – Audio recordings of an animal in distress, or of its predator, played to deter individuals of that species from entering into a fishing area.
Scent deterrents – The application of substances that produce odors to deter non-target species from entering a fishing area.
Decoy deterrents – Approaches that include setting longlines in novel patterns (such as in a sinusoidal shape) to mask the presence of a fishing operation.
Tactile deterrents – The physical prodding of non-target species using a pole, the firing of rubber bullets, or other implements to deter them from interacting with fishing gear.
Vessel chasing (hazing) – Boats are used to chase non-target marine animals from a fishing area.
Weak hooks – Hooks that are strong enough to hold the target catch but straighten out under the pull of larger non-target animals.
T-bars – Welded bars placed in some pot traps to reduce pinniped entrances and predation.
Otter guards – Netting or grids placed over the entrance of traps that prevent the entry of otters while allowing the entrapment of target species such as eels.
Side sets – The placement of fishing gear over the side of a boat rather than the stern.
Night sets – The setting of fishing gear at night.
Alternative offal discharge – Discarding waste as far away from where bait enters the water to lure non-target species away from baited hooks.
Novel bait species – Changing the type or size of bait, such as switching from mackerel to squid.
Flashing lightsticks – Battery-operated lights set at different flicker rates intended to attract fish but not sea turtles.
Reflective/colored buoys – 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 that a fishing operation—and therefore a feeding opportunity—is in the vicinity.
Magnetic deterrents – Magnetic fields created in the vicinity of a fishing activity to deter interaction of non-target species with fishing gear, bait, or target species.
Source: http://www.neaq.org/bycatch/BycatchMatrix11a.pdf