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Experiments were conducted aboard Korean pelagic longline vessels to determine if there were differences in the catch rates of target (tuna and billfish) and bycatch (sharks and other bony fish) species between 3 types of hooks; 4.0 traditional tuna hook (J-4), size 15 circle hook (C15) and size 18 circle hook (C18).  Within the target group significant differences between catch rates were only found between the J-4 and C18 hooks.  In the bycatch species group, significant differences were found between J4 and C15 and between J4 and C18.  Overall, the large circle hook (C18) had the lowest catch rates for tunas and other fish, while small circle hooks (C15) had the lowest catch rates for billfish and sharks.  Any differences in the length of fish caught by the individual hooks were minimal.

An experimental release panel was installed in purse seine nets to determine their ability to release both silky sharks and non-target finfish.  The release panels (5.5 m wide, extending down from the corkline for 11 m) were installed in a portion of the net that forms a "pocket" toward the end of net retrieval.  Dive surveys previously reported that silky sharks tend to segregate and collect in this section of the net.  The release panel was tested during seven purse seine sets, but only two silky sharks (out of 105) exited through this panel. In net observations indicated that sharks and other non-target finfish did not appear to recognize the opening as an escape route out of the net. Despite this initial failure of the release panel, the authors feel refinement of the panel and additional testing is still warranted.

A structured literature review of 103 papers was conducted to characterize trends in shark bycatch research.  Gear modifications, such as hook size/type and net size, were the most commonly evaluated technique to reduce shark bycatch.  Early studies tended to focus on trawl fisheries while more current studies focus on longline fisheries, particularly tuna fisheries. Overall, longline fishery studies made up the majority (44.6%) of published papers and typically were aimed at reducing bycatch.  Later studies also tended to explore potential solutions to bycatch issues.  In terms of trawl fisheries, net size and mesh design were most commonly suggested to reduce shark bycatch, while in longline fisheries, hooks size and type were the most common options suggested. The majority of published papers (40%) focus on the North Atlantic Ocean followed by the North Pacific Ocean (14.4%).  The lack of information on post-release survivorship of sharks made it difficult for the authors to quantify the true amount of bycatch or to recommend handling techniques to fishermen.

Longlines with baited hooks affixed with a block of metal alloy (Nd/Pr) were tested against hooks with a lead weight attached (control), to determine their ability to repel sharks.  Two experiments were conducted in Hawaiian waters, one in the Southern California Bight (SCB) and and one in the Eastern Tropical Pacific off the coast of Eduador.  Significant differences were only found for juvenile hammerhead sharks targeted in one of the Hawaiian experiments.  No significant differences were found during experiments targeting sandbar and tiger sharks during the second Hawaiian experiment, for shortfin mako or blue sharks in the SCB, or for pelagic thresher and blue sharks off the coast of Ecuador.  

Two types of longline sets, night and day, were evaluated for differences in catch composition in Seychelles waters.  Night sets were set at dusk and retrieved at dawn and used shallow baskets targeting swordfish, while day sets were set at dawn and retrieved at dusk and used shallow and deep baskets to target tuna.  The majority (75%) of species, both bycatch and market, were caught during day sets. The proportion of bycatch to target species decreased with depth.  Lancetfish were the main bycatch species during day sets and sharks were the primary bycatch species during night sets.

Blue sharks account for most of the bycatch in the Canadian pelagic longline swordfish fishery. Electropositive metals (e.g. lanthanide) oxidize in seawater and create electric fields, which can alter the behaviors of several species of sharks. Researchers deployed seven sets (6300 hooks) with three hook treatments (standard hooks, hooks with electropositive metals - neodymium/praseodymium - and hooks with lead weights) on the Scotian Shelf in the Northwest Atlantic. Electropositive metals did not reduce the catch of blue sharks or other common shark bycatch species.  

Tests with lanthanide metals were conducted to determine their potential application as a shark repellent in longline fisheries.  Six lanthanide metals were tested (cerium (Ce), neodymium (Nd), praseodymium (Pr), cerium-lanthanum mischmetal (CeLa), praseodymium neodymium metal alloy (PrNdA) and praseodymium neodymium mischmetal (PrNdM)) to quantify their voltage and compare dissolution rates in seawater. A behavioral study was used to determine their efficacy in deterring bonnethead and lemon sharks.  There were no differences in the voltages produced by the metals and their voltages decreased with distance from the samples.  Freshwater produced the greatest voltages, which decreased logarithmically as salinity increased to 10 ppt.  The metals had significantly different dissolution rates, except Nd and Pr.  The time to dissolution ranged from 15.6 hrs for PrDnA to 107.6 for CeLa (lot 2). Behavioral tests were only conducted with Nd, which was not effective in repelling either shark species.

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 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.