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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.  

Shrimp is one of the most valuable fishery resources of Venezuela, with landings about 12 400 t (2007) and worth more than US $35 million. Fishing is carried out along the coast; the industrial trawl fleet used to operate at depths between 10 and 120 m, while fishing with artisanal gears is done close to shore, in coastal lagoons, gulfs and in Lake Maracaibo at depths from 1 to 40 m. The latter represent 84% of landings, mainly from Lake Maracaibo. While only the shrimp is sold by the artisanal fleet, the industrial fleet also sells some fish species, crabs and mollusks. It is been estimated that discards can reach 100 thousand t per year. Due to differences in the spatial distribution of the shrimp and the bycatch, as well as the behavior of the shrimp, more selective fishing systems towards the shrimp were designed, or technological changes in nets were used to restrict the capture of bycatch or facilitate its release after entering the net. In this paper, discards were characterized and various technological changes were tested in nets of common use in shrimp fisheries of Venezuela. The tested systems were: the double lower rope in the industrial trawl; the "fish eye" in the artisanal trawl and the Suripera net. Discards in the industrial fleet were reduced very significantly with the double lower rope, between 26 and 32%, while the commercial catch was maintained or increased. In the artisanal fleet, fish eye allowed reductions of discards between 38 and 54%, without significantly affecting shrimp capture. The Suripera net is very selective, capturing 98% of shrimp, compared to the traditional seine which has 28% efficiency. The possibility of reducing discards is high in industrial or artisanal shrimp fleets operating with trawls, but the seine used by the artisanal fleet operating in Lake Maracaibo may have to be replaced with another more selective gear towards shrimp, like the bottom tangling net. These are examples of how to implement Article 8 of the FAO Code of Conduct for Responsible Fishing (selectivity of the arts in fishing operations) in fisheries of high environmental impact.

The white shrimp, Litopenaeus schmitti, is one of the fishery resources of greater monetary value in Venezuela. This species represents about 90% of the catch of penaeid shrimp of Lake Maracaibo, where one of the largest populations of the species is found within the area of distribution of the species. The remaining catches are made up of three species of the genus Farfantepenaeus (F. subtilis, F. notialis and F. brasiliensis). The mesh opening of beach seine (BS) or Mandinga used to catch shrimp in Lake Maracaibo and Bay El Tablazo is not regulated and varies between 1 ", ¾" and ½ ". On the other hand, since 2005 the bottom tangling net (BTN) with mesh opening of 2" started being used for shrimp capture of shrimp in the Bay of the Tablazo. In 2006 the Suripera net (SN) was introduced on an experimental basis in this area with 1" mesh opening. The objective of the present study was to evaluate the composition by length and weight of shrimp caught with these gears. From February to April 2007 the average size of shrimp obtained with the three gears in the Bay of El Tablazo were compared with ANOVA, and selectivity curve for each gear was obtained according to Sparre and Venema (1995). It was concluded that there were significant differences between the average sizes of shrimp for each gear. The BTN allowed the capture of individuals of greater length and weight, with average size and weight of 14.25 cm and 18,04 g, respectively; followed by the SN with 12,86 cm and 12,80 g and finally the BS with 10,72 cm and 5.72 g. Many of the individuals caught in the BTN and the SN had already reached sexual maturity, and both nets had a low bycatch capture rate (0.26 kg of fish was captured for each kilogram of shrimp). The shrimp caught by these two gear types were mostly adults, which represents higher economic benefits for fishers since larger shrimp have a higher price in the national and international markets. A more sustainable use of resources in Lake Maracaibo would be obtained if the use of the BTN or the SN were implemented in the shrimp fisheries of the region.

Neodymium-iron-boron (Nd2Fe14B) permanent magnets were used to test behavioral responses in spotted catsharks (Scyliorhinus canicula) and thornback skates (Raja clavata). Both species significantly avoided the Nd2Fe14B magnets more often in comparison to the control and procedural control and they fed significantly more from the control and procedural control in comparison to the magnets. The study also demonstrated a correlation between avoidance speed and distance with water temperature. 

Rare earth metals (made of cerium mischmetal) were compared with control treatments of standard circle hooks and inert steel above circle hooks on longline fishing gear to determine if bycatch reduction of spiny dogfish (Squalus acanthias) could be achieved. Results indicated a slight reduction in dogfish bycatch and a greater reduction in catch of longnose skate (Caliraja rhina) on hooks with mischmetal. Problems for using mischmetal commercially include its expense, hazardous nature, and rapid hydrolysis in seawater.

The effect of circle hooks and J-style hooks on the catch composition, catch rates, hooking location and status of release of target and bycatch species were compared on pelagic longline vessels.  There were significant differences in catch rates between the two hook types for bigeye tuna, which had higher catch rates on circle hooks and sailfish (Istiophorus spp.), pelagic stingrays (Pteroplatytrygon violacea), and leatherback sea turtles (Dermochelys coriacea), which had higher catch rates on J-style hooks. Survival of bigeye (Thunnus obesus) and yellowfin tunas (Thunnus albacares) was significantly higher when circle hooks were used, and bigeye and yellowfin tunas, swordfish (Xiphias gladius) and sailfish had significantly higher external hookings when circle hooks were used. The results suggests using 18/0 circle hooks with a zero degree offset could increase the survival of bycatch species while having minimal effects on the catches of target species.

The effect of circle hooks and J-style hooks on the catch composition, catch rates, hooking location and status of release of target and bycatch species were compared on pelagic longline vessels.  There were significant differences in catch rates between the two hook types for bigeye tuna, which had higher catch rates on circle hooks and sailfish (Istiophorus spp.), pelagic stingrays (Pteroplatytrygon violacea), and leatherback sea turtles (Dermochelys coriacea), which had higher catch rates on J-style hooks. Survival of bigeye (Thunnus obesus) and yellowfin tunas (Thunnus albacares) was significantly higher when circle hooks were used, and bigeye and yellowfin tunas, swordfish (Xiphias gladius) and sailfish had significantly higher external hookings when circle hooks were used. The results suggests using 18/0 circle hooks with a zero degree offset could increase the survival of bycatch species while having minimal effects on the catches of target species.

The type (circle 18/0 0 degree offset and J-style 9/0 10 degree offset) and position of hooks in the water column were tested to determine the effects on catch rates and mortality of elasmobranchs in pelagic and bottom longline fisheries in Brazil. Tests were conducted aboard pelagic and bottom longline vessels. Catch per unit effort (CPUE)  for blue shark (Prionace glauca), silky shark (Carcharhinus falciformis) and oceanic whitetip sharks (Carcharhinus longimanus) were significantly higher with circle hooks than with J-style hooks. Silky, blue and oceanic whitetip sharks had a significantly higher mortality at haulback with J-style hooks. Significant differences in hooking location between the two hook types was found for night, blue, silky and oceanic whitetip sharks. These sharks were more commonly hooked externally vs internally.  No significant differences between hook types was found for the CPUE of the sharks on bottom longlines.  Significantly more blacknose sharks (Carcharhinus acronotus) were alive at haulback when circle hooks were used on bottom longlines. Bottom longlines were also used to test for differences in CPUE by fishing depth.  Demersal hooks had significantly higher CPUEs than those suspended in the water column for blacknose sharks, nurse sharks (Ginglymostoma cirratum), and southern stingrays (Hypanus americanus).

Pelagic stingrays (Pteroplatytrygon violacea) are a common bycatch species in the Mediterranean pelagic longline swordfish (Xiphias gladius) fishery. Experimental trials took place in the central Mediterranean Sea from 2005 to 2007 to investigate the importance of bait size, presence and type of light attractors, and hook size and shape on pelagic stingrays. Bait size and light attractants did not have a significant effect on stingray catch rate. Larger J-hooks reduced the stingray capture rate. 16/0 circle hooks had a significantly lower number of stingrays captured than J-hooks, up to 80%

A study was conducted to determine the impact of removing the 'tickler' from in front of ground gear of trawls. The 'tickler' is a length of chain placed in front of the ground gear of trawl gear, which is supposed to increase catches of sharks and rays. Tests were conducted where the 'tickler' was removed and secondary nets (ground gear bags) were placed behind the ground gear to determine the amount and species of fish that escaped capture. The results indicated that removing the 'tickler' from in front of the ground gear reduced the capture of skates and sharks. Therefore, prohibiting the use of 'tickler' chains in critical habitats for skates and sharks could be a beneficial management tool.