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An analysis of records of static net bycatch sampling in the United Kingdom from 1996-2023 found that use of acoustic deterrent devices (ADDs) reduced harbor porpoises bycatch per haul (BpH) to 0.23 of the background rate. BpH increased for harbor seals and grey seals (Phoca vitulina and Halichoerus gryphus) when ADDs were used. Current efforts to reduce harbor porpoise bycatch may be increasing seal mortality in the same fisheries. 

Turtle excluder device (TEDs) with reduced bar spacing may help to reduce bycatch of small sea turtles that can pass through the deflector bars of standard TEDs. A bent bar top opening TED installed at 55°, a bent bar, bottom opening TED installed at 45°, and straight bar, top opening TED installed at 55° were evaluated. None of the TEDs significantly reduced total catch or bycatch. However, the bent bar, bottom opening TED and straight bar, top opening TED both significantly reduced invertebrate (largely jellyfish) catch. 

Solar powered LED lights flashing at a 10% duty cycle (5Hz, 20 min on, 180 mins off) attached to gillnets resulted in a 63% reduction in predicted mean sea turtle bycatch rates. This falls within the range found in previous studies that looked at static lights (40-90% reduction in bycatch), suggesting sea turtle bycatch can be reduced with less power consumption.  

The study tested the effect of Lumo Leads on seabird bycatch and catch rates in the Korean tuna longline fleet. Lumo Leads (previously called "safe leads") add weight to longlines by threading the line through a channel, rather than crimping to the line. This can reduce flyback speed and improve crew safety. Lumo Leads also provide protection from exposure to lead weights, and contain optional fluorescent dye to provide an alternative to single-use glow sticks or electric lights.  Unweighted branch lines caught more than twice the number of seabirds compared to weighted branch lines, although branch weighting alone was not able to completely reduce bycatch. Adding more weight and placing weights closer to the hook increased branch weighting effectiveness as a bycatch mitigation technique. However, catch rate for albacore tuna on weighted lines was significantly lower than on unweighted lines. Catch rate also decreased as weight of the leads increased. There was no effect of branch weighting on catch rates for southern bluefin tuna or yellowfin tuna. 

In response to diamondback terrapin bycatch reduction requirements in North Carolina, crab fishers have proposed a gear modification called a narrow funnel design (NFD), which narrows the funnel entry without altering the continuity of the surface of the trap. NFDs also are installed at the manufacturing stage, eliminating the need to purchase and install traditional BRDs. A second modification proposed by fishers is to make existing funnels more rigid so that it is more difficult for terrapins to enter the pot. This is done through a reinforced funnel design (RFD), where rigid wire is placed on the outside perimeter of the entrance funnel. 

Fisheries-independent trials found no significant impact of BRD use on legal-sized crab catch. In addition, there was a 74% reduction in terrapin bycatch in NFD traps, and a 49% reduction in RFD traps compared to controls. In fisheries-dependent observer trips, NFD pots had significantly higher crab catch compared to standard crab pots, and also caught larger crabs.  25 terrapins were captured in standard pots compared to 11 in NFD pots. 

However, site had a strong effect on both blue crab size and catch, and terrapin bycatch throughout the study. In addition, smaller adult males and juvenile terrapins could still successfully enter the NFD pots, meaning that the use of gear modifications alone may not be sufficient to prevent terrapin bycatch. BRDs should be used in conjunction with other regulatory strategies that prioritize spatial and temporal restrictions to minimize overlap between areas with high densities of terrapins and commercial fishing operations.

The study evaluated the effects of LED colors on CPUE, catch and bycatch rates, and carapace widths in the swimming fisheries in Malaysia, Thailand, and Taiwan. Waterproof flashing LED bulbs (36-48 h of continuous operation with a flash every 2 seconds) were secured to the top of traps using hooks to prevent them from sinking. 

 Blue light showed a positive effect on CPUE, while green and red lights had negative impacts, however none of these trends were significant, and sampling location had a greater impact on CPUE than light treatments. Bycatch levels also varied by light treatment - blue and green lights had the highest levels of bycatch, and the control group had the lowest, with no statistical differences. 

40 trial tows investigated the potential of excluder grids in mitigating bycatch in trawl fisheries in the Northern Levant Sea. Tested gear configurations included a flexible grid with 50mm bar spacing and a rigid grid with 95mm spacing within the trawl extension. The excluder grids significantly reduced bycatch of several elasmobranch species including the velvet-belly lanternshark (Etmopterus spinax) and the blackmouth catshark (Galeus melastomus), as well as some species of bony fish. Sea turtle bycatch also appeared to be reduced although in general, sea turtle bycatch during the trials was low (two individuals in the control gear). However, catch performance of target shrimp species (Aristaeomorpha foliacea and Aristeus antennatus) were also reduced in the gear equipped with BRDs, indicating a trade-off. 

Guarding nets may potentially help mitigate bycatch in trammel net fisheries through the attachment of a supplementary netting panel, typically 10–30 cm high and made of materials that resist entanglement, between the footrope and the main trammel net. Acting as a physical barrier, the panel prevents benthic organisms from becoming trapped. In a small-scale prawn trammel net fishery in Thailand, biomass of non-target organisms was significantly reduced while maintaining target species volume compared with conventional nets. However, the volume of commercial bycatch species was also significantly reduced, which may create a barrier to adoption in small-scale fisheries.  

Study authors conducted a comprehensive review of technical bycatch mitigation measures for sharks for all major commercial fishing gears. Only one technique (changing fishing gear), received a “beneficial” Conservation Evidence (CE) rating (indicating a high level of certainty and effectiveness, and low probability of harm), demonstrating that no single bycatch reduction measure can be applied to all species, fishing gear, and regions. However, many different types of BRTs were rated as “likely to be beneficial”, although additional testing or information is needed. Furthermore, fishery-specific characteristics may mean that BRTs reported as effective in one area or fishery may not be as effective elsewhere. Even when a measure has been rated as being potentially beneficial, implementation in commercial fisheries may still not be feasible due to technical complexities, cost, safety issues, pollution issues, a negative impact on target catch (e.g., electropositive metals), or animal harm/welfare issues. Future research priorities should include development and incorporation of necromones (natural compounds released by decomposing organisms) into commercially viable artificial baits, production of active electrical repellents at scale to encourage uptake, investigating the impact of removal of light-sticks from longlines on shark catch rates, and refinement of circle hook design to reduce shark catch rates. 

Elasmobranch bycatch significantly decreased in bottom-set gillnets in the Gulf of California using orange LEDs, ultraviolet LEDs, green LEDs, and green glow sticks, with orange LEDs being the most effective at reducing bycatch. As a whole, catch of bony fish was not affected by illumination, although responses were taxonomic-specific.