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Experiments were conducted aboard pelagic longline vessels in the western North Pacific to determine the effectiveness of paired tori lines in reducing seabird bycatch.  Paired tori lines (PT) were compared against single tori lines (ST) during these tests.  The most abundant species of bird attacking longlines was the Laysan albatross (Phoebastria immutabilis) (90.2%).  There was a significant difference in the mean number of albatross and shearwater between ST and PT deployments, with the mean number of birds being lower with PT deployments.  PT deployments reduced attacks by albatross by 47.8% and few attacks occurred within 75 m of the stern.  However when ST were deployed, albatross attacked from 25 to 200 m of the stern.  The number of secondary attacks was significantly lower when PT were used compared to ST, with PT deployments reducing secondary attacks by 43.4%.  In addition, no statistically significant difference in the distribution of secondary attacks between port and stern were found when ST were used but statistical differences were found during PT deployments.

A new otterboard door design (Clarck-Y door) was tested in both flume tanks and at sea to compare its possible impact on the seabed compared to an existing door (Cambered vee) design. The two doors had a similar behavior with regard to the attack angle and the magnitude of drag, lift and efficiency coefficients in the flume tank experiment. In the sea trials, the Cambered vee door had higher values for the drag and lift coefficients than the Clarck-Y door and the horizontal door spread was also higher in the Cambered vee compared to the Clarck-Y door. Based on the results of the flume tank experiment, the Cambered vee door had a larger attack angle on the seafloor than the Clarck-Y door. The sea trials suggested the towing force of the vessel greatly influenced the reaction force of the doors.

Use-intensity distributions for 135 satellite-tracked adult leatherback turtles (Dermochelys coriacea) were combined with longline fishing effort to estimate predicted bycatch risk over space and time in the Pacific Ocean. For western Pacific nesting populations, the greatest risk was adjacent to primary nesting beaches in the tropical seas of Indo-Pacific islands. For eastern Pacific nesting populations, the greatest risk was in the South Pacific Gyre. Targeted management should be based on these predicted hotspots to reduce leatherback bycatch.  

This paper is a global assessment of marine mammal (cetacean, pinniped, sirenian, and marine mustelids) bycatch in gillnets and other entangling nets from 1990 to 2011. The authors found that at least 75% of odontocete species, 64% of mysticetes, 66% of pinnipeds, and all sirenian and marine mustelids have been recorded as gillnet bycatch over the past 20 years. 

Direct interactions between longline fisheries and many top predators such as toothed whales result in substatial impacts on fishing activity; depredating species and fish stocks. These issues continue to be a growing concern in fisheries worldwide, including the French Patagonian toothfish (Dissostichus eleginoides) fishery. In this field study, researchers deployed data loggers on killer whales (Orcinus orca) and sperm whales (Physeter macrocephalus) while aboard commercial toothfish demersal longline fishing vessels to gain insight into when, where and how depredation occurs. Data from odontocete tracking loggers and longline accelerometer loggers reveal both species are able to depredate longlines on the seafloor. Findings from this study suggest depredation can occur at anytime during the whole fishing process.      

Field studies were conducted in the Patuxent River, Maryland (U.S.), to quantify the bycatch of cloth-funnel eel pots with small and large openings, and to test the effect of a prototype bycatch reduction device on bycatch and catch.  The bycatch reduction device consisted of a 77 mm PVC ring that was rigged around the narrow end of the flexible eel pot entrance and was designed to physically exclude terrapins (Malaclemys terrapin). Eel pots fitted with these bycatch reduction devices eliminated the bycatch of terrapin turtles but had no effect on the size or number of eels caught. These BRDs also did not increase pot handling time.

Two types of depredation mitigation devices (DMD) were designed and tested aboard pelagic longline fishing vessels targeting tunas and swordfish off the Seychelles. The DMDs were designed to reduce the damage and removal of fish from the fishing gear by predators such as toothed whales and sharks. The first DMD was termed "spider" and was made up of a 100 mm diameter plastic disc with sixteen holes in its outer range and a 37 mm diameter central hole.  Eight 1200 mm long hanging legs were created by placing four polyester strands into the outer holes and the entire system is triggered by a biting fish.  The second DMD, "sock", was designed to cover the fish to hide it from predators through either a net made up of fiberglass mosquito netting or of propylene fiber net.  Shark depredation was significantly higher throughout the surveys than toothed whale depredation, but toothed whales caused more damaged to fish through depredation events. The sock DMD did not affect the catch rates of targeted species or depredation events by either sharks or toothed whales.  These results for the spider DMD were not presented. Trigger rates for the two DMDs were up to 87.3% for the spider and 69.2% for the sock.  The protection rate was as high as 80% for spider but only 15.5% for the sock. Entanglement rates of the DMDs with the fishing gear were low for the spider (3.6%) and higher for the sock (17.8%).  In addition, the use of these DMDs significantly slowed down the fishing process, and therefore additional work into the design and application of DMDs needs to be explored.

Tests were conducted aboard pelagic longline vessels in the Bay of Bengal to determine if there were differences in the catch composition, catch rate, hooking position or length frequency of target and bycatch species caught with circle and J-hooks.  Circle hooks caught similar percentages of both target (46.7%) and bycatch (53.3%) species, while J-hooks caught a higher percentage of bycatch (74.5%) species.  Catch rates for the target species were higher for circle hooks (2.2 individuals/1,000 hooks) compared to J-hooks (1.9 individuals/1,000 hooks).  In contrast, catch rates for the bycatch species were higher on J-hooks (5.6 individuals/1,000 hooks) than circle hooks (2.6 individuals/1,000 hooks).  For the target species, swordfish (Xiphias gladius) had the highest catch rates for both hook types but catch rates were slightly higher on circle hooks.  Close to three quarters (73.3%) of fish were hooked in the mouth when circle hooks were used while only half (53%) were hooked in the mouth, and 38% in the digestive system, when J-hooks were used.  Swordfish caught with J-hooks were slightly larger (mode of 250-269 cm) than those caught with circle hooks (mode 210-229 cm). 

The Dolphin Wall Net (DWN) was designed by these fishermen to reduce dolphin attacks during fishing operations in Kerala, India. Specifically, humpbacked dolphins (Sousa chinensis) tend to congregate in fishing areas, surrounding the ring seine net and removing fish from the net.  This net design can be used by fishermen instead of crackers, which can cause harm to the dolphins. The authors provided fishermen from four stations in Kerala, India (Kasargode, Kozhikode, Ernakulum and Kollam) questionnaires to fill out. The questionnaires were designed to collect information on ring seine fishing operations, dolphin attacks and the structural details of the DWN when it was used.  The authors presented results on the structure of the DWN used by these fishermen but did not report any information regarding differences in bycatch rates between regular ring net operations and those using DWN.

The proven effectiveness of a bycatch reduction technology (BRT) does not guarantee its adoption by fishermen. This case study evaluated the willingness of Sicilian longline fishermen to use relatively large circle hooks (16/0) as a BRT for loggerhead sea turtles (Caretta caretta). Fishermen tested circle hooks with their fishing vessels and their own commercial fishing gear, and their opinnions before and after trials at sea were recorded. Fishermen said that they would be willing to use circle hooks in months with a high probability of bycatch if an economic incentive was provided and there was also public acknowledgement of their efforts.