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Analyses of the Hawaiian (U.S.) pelagic longline fishery were conducted to determine what factors, including hook type (J or circle) and location (sea mount v open ocean), have impacted the catch of both target and bycatch species. Standardized catch rates for all tuna species as well as for blue (Prionace glauca) and oceanic whitetip sharks (Carcharhinus longimanus) were significantly higher when the wider circle hooks were used. However, shortbill spearfish (Tetrapturus angustirostris) and striped marlin (Kajikia audax) catch were significantly lower when circle hooks were used.  No differences in catch rates between the two hook types were seen for bigeye thresher sharks (Alopias superciliosus) or swordfish (Xiphias gladius).  The average swordfish lengths were significantly larger when circle hooks were used, while average lengths for bigeye (Thunnus obesus) and skipjack tunas (Katsuwonus pelamis) were significantly smaller.  There was no difference in the average length between the two hooks types for yellowfin (Thunnus albacares) or albacore tunas (Thunnus alalunga), spearfish or marlins. In addition, the change from J hooks to circle was likely a factor in declining sea turtle bycatch rates. 

Leaders in offshore, deep water pound nets in the Virginia portion of Chesapeake Bay (United States) incidentally take protected sea turtles. To reduce this take, federal resource managers restricted the use of traditional leaders during periods of peak sea turtle strandings. In response to these restrictions, a modified leader was developed. Testing of the new design in 2004 and 2005 indicated that the modified leader significantly reduced sea turtle interactions. Finfish were also sampled from the nets in the study, with results showing no difference in catch weights of four finfish species and the experimental leader harvesting significantly more of a fifth species than the control.

A questionaire administered to the bottom trawling fleet in the western Mediterranean (northeastern Spain) reported 238 bycacth events involving loggerhead sea turtles (Caretta caretta), calculated as a monthly CPUE of .09. The authors dicuss this figure relative to nearby coastal regions and suggest some possible mitigation measures.

Tests were conducted aboard pelagic longline vessels fishing off the coast of Uruguay, to determine the effect of hook type (circle hook vs J-hook) on the catch and length composition of target and non-target species.  Both American and Spanish style longlines were used during these experiments.  American style longlines consist of a 3.6 mm polyamide monofilament mainline with polyamide or polyester buoys lines 9-36 m long.  Spanish style longlines consist of 5-mm polyethlene multifilament mainline with buoy lines (similar in thickness and material to mainline) 12-18 m long.  On the American style longlines, albacore tuna (Thunnus alalunga) and shortfin mako shark (Isurus oxyrinchus) catches were significantly higher on circle vs J-hooks. Catches of other tunas and sharks (blue (Prionace glauca) and porbeagle (Lamna nasus) were also higher on circle hooks, but were not significantly higher.  There was no significant difference in the catches of seabirds or sea turtles between the two types of hooks on the American style longlines.  On the Spanish style longlines, albacore tuna catches were also significantly higher on circle compared to J-hooks, and there was a significant decrease in pelagic stingray (Pteroplatytrygon violacea) catches on circle hooks.  No significant difference in the catch rates of seabirds or sea turtles was seen between the two types of hooks on this type of longline.  There was no significant difference in the length distribution for any species between the two hook types on either type of longline.  There were also no significant differences between hook types for any hooking location of incidentally caught sea turtles.

An observer program assessed the impact of the Costa Rican longline fishery on bycatch species from 1999 to 2010. Observers recorded species, sex, reproductive state, and dimensions of all animals captured. They also recorded information about individual longlines, including location, set and haul back times, hook type, hook number, bait used, target species, and total number of hooks. The longline fishery caught a large number of silky sharks (Carcharhinus falciformis), olive ridley turtles (Lepidochelys olivacea), and pelagic stingrays (Pteroplatytrygon violacea). The authors estimate that 699,600 olive ridleys were caught between 1999 and 2010, including 92,300 adult females. The captures correspond with a decline in nesting populations nearby and statistically significant size decreases in mature turtles. They also observed a decline in the average size of silky sharks. Geospatial analysis of the data indicated that there were temporal shifts in mahi-mahi (Coryphaena hippurus) abundance, but fishing efforts did not shift with abundance. The authors suggest marine protected areas and/or time area closure to reduce the bycatch of sea turtles and sharks.  

Two new types of turtle excluder devices were tested in the Northern Australia prawn fishery to determine their ability to exclude sea turtles from capture.  The first design, JT 1, had a large escape opening across the width of the top panel ahead of the codend, with the forward edge of the escape weighted down and the aft edge buoyed.  This design did not prevent the capture of sea turtles or other large sharks and rays but caught 6.6% more tiger prawns (Peneaus sp.) and 10.5% more endeavour (Metapenaeus sp.) prawns than the standard net.  The second design, JT 2, had two large holes (200 cm long x 30 meshes deep) cut into the side panels of the net ahead of the codend with the aft edge weighted and two standard (40 mesh wide) bigeye escape panels were added between the two side openings.  The second design also did not prevent the capture of sea turtles or other large sharks and rays but did reduce finfish bycatch by 5% and caught 5.2% more tiger prawns and 6.9% more endeavour prawns compared to standard nets.

This study attempted to hydrodynamically optimize Turtle Excluder Devices (TEDs) in trawl fishing nets in order to balance bycatch reduction with operational efficiency. Researchers conducted flume test experiments on different TED configurations (bar spacing, installation angle, and flow velocity) in a model shrimp trawl, and used Fast Fourier Transform analysis (FFT) to understand the hydrodynamic force oscillations. The presence of a rigid TED increases mean codend drag by 26.2% to 42.1% compared to an empty codend, with drag amplifying as bar spacing decreases and as installation angle and flow velocity increase. A Genetic Algorithm framework identified the optimal TED configuration as an 88 mm bar spacing, a 60° installation angle, and a 0.6 m/s flow velocity. This optimized configuration achieved substantial improvements, reducing mean drag by 45.25%, suppressing drag oscillation amplitude by 64.87%, and improving relative codend stability by 28.76%. 

This study examines the occurrence of cumulative cold events in the Gulf of Ulloa, Baja California (Mexico), defined as sea surface temperatures (SST < 18°C) for ≥5 consecutive days, as a basis for developing an operational environmental indicator to support adaptive fisheries management and reduce sea turtle bycatch. Results indicate a clear seasonal pattern, with the highest frequency of cold events between March and June, coinciding with intensified coastal upwelling and the residence of juvenile Caretta caretta. Eighteen critical areas of persistent environmental conditions were identified as overlapping with areas of turtle-fishery interactions. This indicator could provide near-real-time environmental information to anticipate sea turtle vulnerability and support conservation decisions without relying on static fishery closures. 

This study assessed the interaction of leatherback sea turtles (Dermochelys coriacea) with fixed-gear fisheries in high-latitude seasonal foraging habitat (Atlantic Canada), using sightings data from 1998-2014. Most reports came from coastal Nova Scotia and Newfoundland, with reports peaking in the mid-to-late 2000s. The majority of reported entanglements came during the summer months (July and August), and were with pot gear and trap nets. 

A cumulative impact analysis framework integrating species habitat suitability and fishing effort data, stratified by gear type, was used to assess bycatch risk for threatened and protected species in China's seas and adjacent waters. Across all taxonomic groups examined, including seabirds, sea turtles, marine mammals, elasmobranchs, bony fishes, and benthic invertebrates, the highest bycatch risk was concentrated between 23°N and 25°N. For marine mammals and sea turtles, elevated risk was concentrated along China's southeastern coast, extending through inshore waters from the Yangtze River Estuary south to 20°N, with trawls and gillnets contributing most significantly to risk. Seabird bycatch hotspots were primarily located around islands, bays, and estuaries north of 20°N, where gillnets posed the greatest threat. Elasmobranchs experienced high bycatch risk from the Taiwan Strait to the Yangtze River Estuary and around Jeju Island, and were the most vulnerable taxa group overall. Bycatch risk for benthic invertebrates was largely restricted to narrow nearshore areas and was associated primarily with dredging activities. The study also found that marine protected areas generally exhibited lower bycatch risk than surrounding waters.