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A laboratory study was conducted to determine the impact of an electrical field on mortality rates and histological changes on model marine organisms. The tests were carried out to provide more information on the impact of electrotrawling om marine species. Two species of invertebrates, brown shrimp (Crangon crangon L.0) and king ragworm (Alita virens S.) were used as model species for crustaceans and polycheates, respectively. Specimens were expose to a homogeneously distributed electrical field varied by frequency (5-200 Hz), electrical field strength (150-200 Vm-1), pulse polarity, pulse shape, pulse duration (0.25-1 ms), and exposure time (1-5 s). Shrimp tended to do a tail flip in response to some electric pulses and ragworm showed a squirming response independent of the frequency. There were no increases in mortality or injuries for either species with any of the pulse parameters tests. Shrimp exposed to 200 Vm-1 showed significantly higher severity of intranuclear baculoform virus infection. 

Estimates of post-release mortality (PRM) rates for discarded bycatch are largely unknown across marine fisheries and represent a substantial source of uncertainty when estimating total fishery mortality. One way to predict PRM is through the use of reflex action mortality predictors (RAMP), whereby the presence or absence of target reflexes and known post-release fate are used to create a delayed mortality model. We employed reflex impairment assessments in concert with post-capture caging and video monitoring to predict 5-d PRM rates for the deep-sea giant isopod Bathynomus giganteus , a common bycatch species in numerous deepwater fisheries worldwide, and also considered the factors contributing to mortality. Mortality rates 5 d post-capture ranged from 50 to 100% and both RAMP scores and time at the surface were significant predictors of mortality, although our conclusions regarding the effect of surface time are limited. In-cage video documented little movement within the 24-h monitoring period following capture, and it appeared that surviving individuals often fed within the holding period after cage deployment. Our results suggest that PRM in B. giganteus is common and that this unaccounted source of mortality should be quantified for other deep-sea crustaceans captured as bycatch.

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.

 Data was collected on the relative performance of single and multiple round, rectangular, and square escape gaps across three fishing operations. Compared to control traps, those with escape gaps maintained catches of legal-sized P. pelagicus, but caught 51–100% fewer undersized individuals. Generally, rectangular escape gaps and especially multiple configurations were the most effective. Escape gaps represent a low-cost option for minimizing interactions with unwanted catches throughout the fishery.

The individual and cumulative effects of increasing mesh size and installing three escape gaps (36 × 120 mm) in collapsible‐netted round traps were assessed to address concerns associated with excessive discarding in an Australian portunid fishery. Compared to conventional traps of 56‐mm mesh throughout, those with the same mesh size and escape gaps caught significantly fewer (by 54%) undersized blue swimmer crabs, Portunus armatus, and yellowfin bream, Acanthopagrus australis (by 64%). Irrespective of escape gaps, simply increasing the mesh size to 75 mm did not significantly affect catches of undersized P. armatus, although 87% fewer A. australis were retained. Traps with both 75‐mm mesh and escape gaps maintained reductions of A. australis, but had a clear cumulative effect on P. armatus selection, retaining 84% fewer undersized individuals across a larger size at retention. The results support using escape gaps in existing conventional traps, but illustrate the need to configure the minimum legal mesh size to approach the desired target size of P. armatus as a precursor to maximizing trap selectivity. 

In 2015, NPF Industry Pty Ltd launched the Northern Prawn Fishery’s Bycatch Strategy 2015-2018 with the vision to reduce small bycatch by 30% in three years. A key component of the strategy was industry innovation and through this process the Kon’s Covered Fisheyes Bycatch Reduction Device (BRD) was developed.In 2016, at-sea testing of the Kon’s Covered Fisheyes Bycatch Reduction Device (BRD) was conducted in the Gulf of Carpentaria to determine its effectiveness in reducing small bycatch in the tiger prawn fishery compared to a currently legislated device. The device was found to significantly reduce small bycatch by approximately 36.7%, with commercial prawn catch increasing by an average of 0.5%. The device proved to be easy and safe for crew to use and due to the significant reduction in bycatch, the time taken for crew to process the catch was reduced.

This study tests the impact of skids placed on scallop dredges in various habitats to reduce seabed impact; skids raise the scallop collecting bag 10-11cm off the seabed. The modified skid dredge caught more marketable scallops per unit area, but also retained more bycatch overall and more undersize scallops. Results were habitat specific.

This study examined the effectiveness of various sizes of guarding nets to reduce bycatch (specifically crustaceans) in cuttlefish trammel net fisheries. All nets did siginificantly reduce crustacean capture, notably spider crabs, but only the smaller mesh guarding net (20mm instead of 40mm) had no significant impact on target cuttlefish catch. However, guardnets may benefit fishers overall by avoiding later delays in disentangling bycatch and damage to gear. 

This summary study analyzes unintended horsehoe crab (Tachypleus tridentatus) bycatch in trawl and gillnet fisheries in the Letzhou Gulf, China. Estimates show at least 9120 ± 315 horseshoe crabs are caught annually. Bycatch rates increase in spring and autumn, and are higher in gillnet fisheries compared to trawl fisheries. The study also highlights several zones/areas of the Letzhou Gulf with "abundant shoal resources" and higher bycatch rates.

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.