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The Pacific hake (Merluccius productus) midwater trawl fishery is the largest groundfish fishery off the U.S. West Coast by volume. However, bycatch of Chinook salmon can be an issue as Endangered Species Act (ESA)-listed Evolutionarily Significant Units represent a portion of the total Chinook salmon bycatch. This study investigated the influence of artificial illumination on Chinook salmon behavior and their escapement out of a bycatch reduction device (BRD) in a Pacific hake midwater trawl. Artificial illumination can influence where Chinook salmon exit out of the BRD and can also enhance their escapement overall. As conservation of ESA listed Chinook salmon is an ongoing management priority, this research contributes new information on how artificial illumination can minimize adverse interactions between the Pacific hake fishery and Chinook salmon.

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. However, the TED preferentially released larger-sized individuals, meaning that smaller-sized individuals and species, including the "Critically Endangered" Bancroft's numbfish, were still captured by the trawl. Since the modified TED was generally successful in reducing important elements of elasmobranch bycatch, future study will extend the study to determine the impact of the TED on the capture rate of the target seabob shrimp. 

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. Generally, the study showed that TEDs facilitated the escape of large elasmobranchs, including several species of conservation interest (the scalloped hammerhead, Sphyrna lewini and the zebra shark, Stegostoma fasciatum). Bar space and orientation were important TED design factors affecting the escape of elasmobranchs. Top-shooter TEDs enabled more Carcharhiniformes (“ground sharks”, including requiem sharks and hammerhead sharks) to escape penaeid trawls, while bottom-shooter TEDs increased the escape of Myliobatiformes (rays, including stingrays and cownose rays). However, the TED bar space that facilitates maximum escape of elasmobranchs while maintaining catch of the target species is more difficult to quantify given the low catch rate of elasmobranchs in the trawls. 

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. Diamondback terrapin entrapment events increased in frequency over the course of the study period, suggesting that repeated exposure to the crab pots increased an individual’s likelihood of entering a pot. Consumable baits had the greatest effect on terrapin entrapment, relative to the presence of conspecifics and non-baited crab pots. However, further study is needed to determine if there is a type of bait that is more attractive to crabs, but not to terrapins. Use of a combination of conservation measures, including BRDs, spatial and temporal crabbing closures, and changes in bait type, remain the most likely to be successful option in protecting terrapin populations.

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. The color of the selective device should therefore be investigated further with the aim of increasing selection efficiency. Further development of the software could be done to identify species and size of the fish and assess the effectiveness of a selective device by species and size.

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. However, the illuminated trawl caught similarly or significantly more rockfish (Sebastes spp.) and flatfish than the unilluminated trawl.

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). For illuminated nets, bycatch probability per set was reduced by up to 74.4 % for sea turtles and 70.8 % for small cetaceans in comparison to non-illuminated, control nets. For seabirds, nominal BPUEs decreased by 84.0 % in the presence of LEDs. Target species CPUE was not negatively affected by the presence of LEDs. This study highlights the efficacy of net illumination as a multi-taxa BRT for small-scale gillnet fisheries in Peru. 

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. However, previous studies have found that SMPs do not significantly increase non-target fish escapes because there is a low probability of fish making contact with the panel.This study aimed to determine whether i) adding white LED lights at different positions of the SMP, ii) changing the size of the SMP, and iii) changing the position of the SMP in the trawl improved the release efficiency of a square mesh panel (SMP) installed at the top panel of the extension piece of the trawl. The study focused on reducing catch of undersized hake (Merluccius merluccius), a main target species for the Basque multispecies trawl fishery in the Bay of Biscay, and blue whiting (Micromesistius poutassou), which is considered a “choke” species in the fishery (one with a low quota). The position of LED lights did not significantly affect the SMP’s release efficiency for any species. However, increasing panel size increased escapes of blue whiting, and placing the SMP in the lower net panel increased escapes of hake. These species-specific results highlight the challenge of simultaneously improving the selective properties of gear for species with different behavior, especially in mixed demersal fisheries.

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.

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.