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Performance of a bycatch reduction device in the shrimp fishery of the Gulf of California, Mexico

A square mesh/extended funnel bycatch reduction device (BRD) tested in the bottom trawl shrimp fishery in the Gulf of California decreased bycatch by 40% when compared to control trawls. On average, the BRD excluded 37% of finfish species, including the endangered Totoaba macdonaldi, but it also reduced shrimp catch by approximately 7%.

Design and assessment of two gear modifications to reduce the benthic impact and fuel intensity of prawn trawling in Australia

Modified ground gear, known as batwing otter boards, created less disturbance to the seafloor than traditional otter boards in the Australian prawn trawl fishery, decreasing bycatch of benthic squirts and starfish by approximately 85-90%. The target catch of both prawns and scallops decreased by about 10%. Modified ground gear, called soft-brush ground gear, reduced bycatch of starfish by 35% but increased bycatch of nektobenthic species including small crabs and non-target prawns in the Australian prawn trawl fishery.

Impact of a bycatch reduction device on diamondback terrapin and blue crab capture in crab pots

A trap modification reduced bycatch of diamondback terrapins (Malaclemys terrapin) in a blue crab (Callinectes sepidus) pot fishery in the Patuxent River, a tributary of the Chesapeake Bay. Three wire modifications were tested and found that terrapin bycatch can be reduced without decreasing the number or size of captured crabs.

On electrical fishing for brown shrimp (Crangon crangon) II. Sea trials

Modified ground gear in the North Sea brown shrimp (Crangon crangon) bottom trawl fishery utilized electromagnetic deterrents and a raised groundrope to obtain catch separation. Preliminary results of the modified gear indicate a selective effect on fish and invertebrate species. Bycatch of various fish and invertebrate species were decreased with a negligible effect on shrimp catch. The results showed great promise, but the authors indicate more testing is necessary.

A field experiment using acoustic alarms (pingers) to reduce harbour porpoise by-catch in bottom-set gillnets

Pingers were tested to reduce harbour porpoise (Phocoena phocoena) bycatch in bottom-set gillnets in the Swedish Skagerrak Sea. During the experiment, no harbour porpoise were caught in control or experimental gillnets, possibly as a result of a combination of factors including displacement of porpoise, high prey availability in other areas, or pingers acting as passive reflectors. Pingers did not affect the catch of target species, including cod and pollock.

Benefits of square mesh codends in Queenslands scallop and prawn trawl fisheries

Preliminary results indicate square mesh codends on trawl gear, used with turtle excluder devices, decreased bycatch of small fish, small crabs, sea urchins, shellfish, and undersize scallops when compared to standard diamond-mesh net codends. Catch of targeted scallop and prawn were not reduced by the square mesh codends.

Seabird mortality at trawler warp cables and a proposed mitigation measure: A case study in Golfo San Jorge, Patagonia, Argentina

A warp cable modification (plastic cone attached to each warp cable) reduced seabird bycatch in the high-sea Argentine hake (Merluccius hubbsi) trawl fishery. The two most abundantly captured seabirds prior to the attachment of plastic cones were the Kelp gull (Larus dominicanus) and the Black-browed albatross (Thalassarche melanophrys).

Reducing seabird bycatch in longline fisheries using a natural olfactory deterrent

School shark (Galeorhinus galeus) liver oil dripped behind fishing vessels in the northern New Zealand snapper (Pagrus auratus) longline fishery reduced seabird numbers and dives on baits when compared to canola oil and seawater control treatments. The shark liver oil did not affect the number of target snapper, gurnard (Chelidonicthys kumu), kaha-wai (Arripis trutta), or trevally (Pseudocaranx dentex) caught.

Experiments in gear configuration to reduce bycatch in an estuarine squid-trawl fishery

Five codend designs and four behavioral-type bycatch reduction devices were tested to reduce fish bycatch in the broad squid (Photololigo etheridgei) and bottle squid (Loliolus noctiluca) trawl fishery in New South Wales, Australia. Reducing posterior circumference, increasing mesh size, and changing to diamond-shaped mesh did not improve trawl selectivity. A square-mesh codend did improve selectivity by reducing fish bycatch by 71% without reducing squid catch.

Mitigation of seabird mortality on factory trawlers: trials of three devices to reduce warp cable strikes

Three seabird bycatch mitigation measures, tori lines, warp scarer, and Brady baffler, were tested on trawlers and compared with a control treatment of no mitigation measure. Each mitigation measure reduced seabird mortalities; however, the tori lines, followed by the warp scarer, were much more effective at reducing seabird contact with fishing gear than the Brady baffler.

Mitigation of incidental mortality of Australian sea lions in the west coast rock lobster fishery

Pot-gear modifications or sea lion exclusion devices (SLEDs) were tested in the Australian West Coast rock lobster pot fishery to reduce bycatch of Australian sea lion pups and juveniles. Although low levels of interactions in this preliminary study make testing the efficacy of the gear modification difficult, early tests indicate the SLEDs do not reduce rock lobster catch in shallow water. In deep water, redneck-batten and redneck-bolt pots reduced lobster catches but in fingerneck-bolt pots, there was no significant difference in catch from normal pots.

Effectiveness of bycatch reduction devices (BRDs) in the ocean shrimp (Pandalus jordani) trawl fishery

The requirement, in 2003, that trawl vessels fishing for ocean shrimp use bycatch reduction devices (BRDs) has reduced fish bycatch by between 66% and 88% from historical (pre-BRD) levels. Data collected from a trawl experiment testing a rigid-grate BRD with 19-mm bar spacing suggest that bycatch in the ocean shrimp fishery can be reduced further, perhaps below 5% of total catch.

Reducing sea turtle interactions in the Hawaii-based longline swordfish fishery

To reduce turtle interactions, regulations for the Hawaii-based longline swordfish fishery required vessels to switch from using a J-shaped hook with squid bait to a wider circle-shaped hook with fish bait. Analyses of observer data showed that, following the introduction of the regulations, significant and large reductions in sea turtle and shark capture rates occurred without compromising target species catches.

Acoustic pingers eliminate beaked whale bycatch in a gill net fishery

Acoustic pingers reduced bycatch of beaked whales to zero in the California drift gill net fishery.

Hydrodredge: Reducing the negative impacts of scallop dredging

A hydrodredge was tested using water pressure created from the hydrodynamics of the gear to lift scallops out of the seabed. The hydrodredge when compared to a more traditional dredge increased catch of surface-dwelling scallops but decreased catch of deeper-dwelling scallops. Bycatch of starfish, crabs and urchin were less likely to suffer fatal injuries in the hydrodredge.

Effects of eliminating shallow hooks from tuna longline sets on target and non-target species in the Hawaii-based pelagic tuna fishery

Longlines were set at depths greater than 100m using weighted lines to reduce bycatch of recreationally important fish species and protected species such as seabirds and sea turtles. While bigeye tuna catch rates were consistent between control and experimental sets, bycatch rates increased for sickle pomfret and opah but decreased for wahoo, dolphinfish, blue and striped marlin, and shortbill species. These species are generally not targeted but retained for their commercial value. Bycatch of sharks and pelagic stingrays did not differ between the experimental and control sets.

Assessment of seal-fishery interactions in the winter blue grenadier fishery off west Tasmania and the development of fishing practices and Seal Exclusion Devices to mitigate seal bycatch by factory trawlers

Several designs of seal exclusion devices (SEDs) were tested to reduce bycatch of seals in the winter blue grenadier trawl fishery. A 'top-hatch' SED, or one with a top-mounted escape hatch, resulted in the lowest occurrence of seal bycatch than any other SED design or than nets without a SED. The SED prevented entry into the net codend where drownings occurred. They also successfully expelled seals and limited access into the net via the escape hatch. Cameras are needed to verify the results.

Do rare-earth metals deter spiny dogfish? A feasibility study on the use of electropositive

A rare-earth metal alloy (cerium/lanthanide) was tested to determine if it would reduce bycatch of spiny lobster on longlines and rod and reel gear in the Gulf of Maine. Laboratory and field trials showed no significant reduction in dogfish catch.

Field investigation of rare-earth metal as a deterrent to spiny dogfish in the Pacific halibut fishery

Rare earth metals (made of cerium mischmetal) were compared with control treatments of standard circle hooks and inert steel above circle hooks on longline fishing gear to determine if bycatch reduction of spiny dogfish could be achieved. Results indicated a slight reduction in dogfish bycatch and a greater reduction in catch of longnose skate on hooks with mischmetal. Problems for using mischmetal commercially include its expense, hazardous nature, and rapid hydrolysis in seawater.

Reducing elasmobranch bycatch: laboratory investigation of rare earth metal and magnetic deterrents with spiny dogfish and Pacific halibut.

Two rare earth metals (neodymium-iron-boride magnets and cerium mischmetal) attached to baited hooks were tested in a laboratory study against inert metal controls to determine the effects of spiny dogfish and Pacific halibut. Spiny dogfish attacked and consumed fewer baits with mischmetal than for the control or magnets. Magnets did not deter dogfish from eating baits, and Pacific halibut showed no reaction to either rare earth metal.

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