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A double codend was compared to the standard codend in the Clarence River penaeid trawl fishery in southeastern Australia, to determine its effects on total catch, retained and discarded school prawns (Metapenaeus macleayi), sizes of discarded prawns, discarded fish and immediate and short-term mortalities of discarded juvenile school prawns.  The only significant difference between gear types was the immediate and short-term discard mortalities, which were reduced by 13.8% and 17.1% respectively when the double codend was used.  Additional analysis also showed that mortalities of school prawns increased with the quantity of jellyfish. 

The number of floats and hanging ratio of trammel nets were altered in two experimental nets and compared to a standard trammel net to determine the impact on reducing the bycatch of purple dye murex, mantis shrimp and crabs.  The first experimental net had more floats than the control net in addition to a guarding net and the second experimental net had the same number of floats as the control net, with the addition of a guarding net.  During the first trial only experimental net 1 and the control net were compared and in the second trial all three nets were compared.  During the first trial, the experimental net caught 17% fewer prawns, the target species, 44% fewer crabs and mantis shrimp and 49% fewer murex than the control net.  During the second trial, experimental net 1 caught 66% fewer crabs, 27% fewer mantis shrimp and 32% fewer murex than the control net.  Experimental net 2 caught slightly fewer prawns (2%), 51% fewer crabs, 17% fewer mantis shrimp and 26% fewer murex than the control net. 

A new toothless dredge design called the "Newhaven" was tested in the Isle of Man queen scallop fishery, to determine it's effect on both catch and bycatch.  This new dredge design caught significantly more queen scallops compared to the traditional tooth dredge.   However, there was no significant difference between the abundance of bycatch between the two dredge designs.  Bycatch species composition between the two dredge types was relatively similar but the "Newhaven" dredge did catch a significant number of dogfish.

Studies were conducted aboard beam trawlers in the North Sea to determine the performance of pulse beam compared to conventional tickler chain beam trawlers.  Overall the pulse beam trawl caught 68% less than the conventional trawls.  Specifically, the pulse beam trawl caught significantly fewer plaice and sole compared to the conventional beam trawl. There was no significant difference in catch rates of undersized plaice between the two gears but the pulse beam trawl caught significantly less undersized sole.  Pulse beam trawls caught more turbot and brill (78%-131%) than conventional trawls but fewer cod (15%-60%).  In addition, catch rates of bottom species, including sandstar, common starfish and swimming crabs, were significantly less when the pulse beam trawl was used.

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.

This is a comprehensive, critical overview of studies on the use of electrotrawling in the North Sea. Electrotrawling, involves replacing the tickler chains or bobbins with electrical stimulation. The result is reduced contact with bottom habitats, reduced fuel costs and reduced discards. An overview on the current status and implementation of this technique in flatfish, shrimp and razor clam fisheries is provided. In terms of the flatfish fisheries, while electrotrawling is a promising alternative, potential negative impacts (i.e. safe range of pulse parameters, differences in sensitivities of species, effects on early life stages, long-term effects, impact on electrosensitive fish and potential electrolysis effects) were not quantified. Regardless, it appears that electrified trawls are superior to conventional trawls in terms of ecological impacts, management and carbon footprint.

This is a comprehensive, critical overview of studies on the use of electrotrawling in the North Sea. Electrotrawling, involves replacing the tickler chains or bobbins with electrical stimulation. The result is reduced contact with bottom habitats, reduced fuel costs and reduced discards. An overview on the current status and implementation of this technique in flatfish, shrimp and razor clam fisheries is provided. In terms of the flatfish fisheries, while electrotrawling is a promising alternative, potential negative impacts (i.e. safe range of pulse parameters, differences in sensitivities of species, effects on early life stages, long-term effects, impact on electrosensitive fish and potential electrolysis effects) were not quantified. Regardless, it appears that electrified trawls are superior to conventional trawls in terms of ecological impacts, management and carbon footprint.

A study was conducted aboard vessels from the South Australian Spencer Gulf prawn fishery to examine the utility of a mechanical-separating bycatch reduction device. The fishery targets prawns but has bycatch of giant cuttlefish (Sepia apama) and blue swimmer crabs (Portunus armatus). Conventional codends were tested against small and large Nordmore-grids set at high and low grid angles. Both grids resulted in bycatch reductions. The number and weight of cuttlefish were reduced by 50.4% and 59.7%, respectively, when the small grid was used. The large grid resulted in a reduction of 33.5% in number and 36.6% in weight of cuttlefish. Crab bycatch was reduced by 40.2% (number) and 47.5% (weight) when the small grid was used, and 40.9% (number) and 38.1% (weight) when the large grid was used. A reduction in prawn catch (weight) was observed when the small grid was used compared with the large and control grid.

A mechanical separating bycatch reduction device was tested in the Spencer Gulf king prawn trawl fishery to reduce the incidental capture of giant cuttlefish (Sepia apama) and blue swimmer crabs (Portunus armatus). Different sizes of Nordmore grids were tested. Two Nordmore grids were inserted into the posterior extension sections and triangular escape exits were cut out. One grid was located in the extension with an angle of -45 degrees (small grid) and the second large grid was set at a 30 degree angle in the extension. The large Nordmore grid significantly reduced bycatch of cuttlefish and blue swimmer crabs by 30-50%. Catches of king prawn were not impacted by the use of Nordmore grids.