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In the Mediterranean Sea, trawl nets have high levels of bycatch of protected species, including the loggerhead turtle (Caretta caretta), with high rates of mortality. A new flexible Turtle Excluder Device (TED) was tested for the first time on a commercial scale in the Mediterranean Sea to assess its effectiveness in reducing bycatch. The results did not show any significant (α = 0.05) loss in terms of commercial catch weight, but resulted in a significant reduction of debris in the codend of the nets in comparison to traditional nets.

To improve bycatch mitigation of chondrichthyans, reptiles and cetaceans for a tropical demersal fish-trawl fishery, species-specific responses to bycatch reduction devices (BRDs) were investigated using both in situ subsurface and onboard observations.

The study tested the use of a modified turtle exluder device (TED) - using substantially reduced grill spacing - in order to reduce elasmobranch bycatch in the Guyanese seabob shrimp fishery. The use of the modified TED resulted in a significant reduction (by 40%) of the bycatch rate of elasmobranchs. The TED also was highly effective in reducing the capture of three "Near Threatened" ray species.

The study quantified the impact of turtle excluder devices (TEDs) on the catches of various elasmobranchs caught off northern Australia using data collected during a previous study (Brewer, et al., 2006). The effect of fish size and various aspects of TED design such as grid orientation, grid angle, and bar space were quantified to determine their effect on the escape of elasmobranchs from shrimp trawls. The relatively low number of elasmobranchs encountered during sampling resulted in a lack of power to isolate the effects of the various factors tested.

The attractiveness of nine “bait” types were assessed ex situ on twelve wild-captured male diamondback terrapins in a commercial blue crab (Callinectes sapidus) pot fishery : no bait, chicken, shrimp, freshwater fish, presence of one female terrapin, presence of two female terrapins, presence of one male terrapin, presence of two male terrapins, and presence of one male terrapin and one female terrapin.

The focus of this study was to compare two selective devices in a trawl by automated counting of fish escapements through each selective device (a white and black square mesh panel) based on video sequencing and an algorithm for automated object detection and tracking. The software detected a significant difference in fish escapement rate according to net color- 60% of all fish escaped through the white panel, suggesting that net color influences the escape rate of fish.

This study examined the extent that eulachon (Thaleichthys pacificus) and groundfishes escape trawls in response to artificial illumination. Using a double-rigged trawler, catch efficiencies were compared for ocean shrimp, eulachon, and groundfishes between an unilluminated trawl and a trawl illuminated with five green LEDs along its fishing line. Results showed a significant reduction in the bycatch of eulachon and yellowtail rockfish (Sebastes flavidus) in the presence of illumination.

Solutions to mitigate cetacean bycatch have targeted specific fisheries and gears, however, these targeted mechanisms can be effective if interactions occur only between a particular population and gear type or fishery. Most dolphin and whale populations face incidental capture from multiple fisheries and gears. Accordingly, broad-scale spatial approaches to mitigation are needed to address bycatch across multiple species at the scale at which the species occur.

Researchers deployed LED lights on the floatlines of paired gillnets (control vs illuminated net) during 864 fishing sets by small-scale vessels departing from three Peruvian ports between 2015 and 2018. Bycatch probability per set for sea turtles, cetaceans and seabirds as well as catch per unit effort (CPUE) of target species were analyzed for illuminated and control nets using a generalized linear mixed-effects model (GLMM).

Square mesh panels (SMPs) have been proposed as a bycatch reduction measure that can increase the escape of non-target fish species without significantly changing the economic value of the catch.

The selectivity of the Skagerrak standard trawls were compared with a trawl differing only in the belly length, being 37% shorter. The trawls fished shrimp above 19 mm carapace length equally, while catch rates of shrimp below 15.5–16 mm carapace length in the shorter trawl were more than halved. Bycatch of Norway pout (Trispterus esmarkii) was slightly reduced in the shorter trawl, unrelated to fish length.

In south-eastern Australia, baited, round traps (comprising 50–57-mm mesh netting) are used to target giant mud crabs (Scylla serrata) and blue swimmer crabs (Portunus armatus) in spatially separated fisheries.  Two experiments assessed the utility of (1) traps partially or completely covered in larger mesh (91 mm to match the minimum legal size of the smaller P. armatus), and (2) any cumulative benefits of fitting species-specific escape gaps.

This study developed fishing traps made with plastic that included adjustable escape gaps for the release of undersized fishes. The unique improved selective fishing traps operate in shallow water of 1-2 meters depth. Traps are set against the flow of water current to aid movement of fishes into the traps. The average catch per month of matured fishes of table sizes caught by the invention is approximately 61% compared with approximately 23% fishes usually caught by the traditional traps.

A software tool was developed to assess observer coverage with respect to several objectives for documenting or estimating rare-event bycatch.

The study tested the vocalization response of harbor porpoises (Phocoena phocoena) to two different acoustic pingers, the AQUAmark 100 (20-160 kHz) and the AQUAmark 300 (10 kHz). Trials in Scotland and Denmark found that the AQUAmark 100 resulted in a significant reduction of porpoise vocalizations at 0,200, and 400 meters distance from the pingers. The vocalization behavior reveal no signs of habituation. Studies of the AQUAmark 300 resulted in a significant reduction of vocalizations at 0m and no significant reduction at 300m.

A long-term study assessed the efficiency of acoustic pingers (AQUAmark 100, 20-160kHz) in reducing the encounter rates of finless porpoises (Neophocaena spp.) with fishing nets. The study used a passive recorder to obtain acoustic encounter rates of echolocating finless porpoises over two eight-month periods. Encounter rates were significantly lower in periods when pingers were in use, but this effect decreased over time. By the end of each study period, the number of encounters was greater than those during periods without pingers, suggesting that habituation had occurred.

The study combined fisher questionnaires, acoustic monitoring, and participatory experiments to investigate the occurrence of bottlenose dolphins (Tursiops truncates) in the gillnet fisheries of Northern Cyprus. Dolphins were present in fishing grounds throughout the year, and were detected at 28% of net sets. Net damage was six times greater when dolphins were present during sets. Use of an acoustic pinger (AQUAmark 200, 5-160kHz) was tested, but had no significant effect on dolphin presence. 

The experiment evaluated the effectiveness of two types of pingers (Aquamark 100 and Aquamark 200) to reduce the bycatch rate of harbor porpoise (Phocoena phocoena) in a set gillnet fishery in the Black Sea. The study also evaluated the effects of the pingers on catch of target and non-target fish species. There was no significant difference in catch of target and non-target fish species in trials with pingers versus control sets.

 Preliminary field studies were carried out on a potentially cetacean-friendly acoustic deterrent system for seals (played using underwater loudspeakers). The “smart seal deterrent signal” produces a startle response in seals rather than an aversion to a very loud noise, and is transmitted at a sound level which is not harmful to seals, even at very close distances.

The study investigated the effects of bait size and hook size on catching efficiency and size selectivity in Icelandic longline fisheries targeting cod (Gadus morhua), haddock (Melanogrammus aeglefinus), tusk (Brosme brosme), ling (Molva molva) and wolffish (Anarhichas lupus). Five sizes of hooks and two sizes of bait were tested. Larger bait (30 grams vs. 10 grams) caught more large fish and fewer small fish of all species, with the exception of ling. Additionally, haddock catches were reduced by 57% when the large bait was used.