Selectivity of 50 mm T0 and T90 codends for commercial shrimp species in the Turkish deepwater trawl fishery, Eastern Mediterranean

Abstract

Summary The study compared the selectivity of 50 mm mesh size conventional (T0) and 90° turned mesh (T90) demersal trawl codends for four commercial shrimp species (Aristaeomorpha foliacea, Aristeus antennatus, Parapenaeus longirostris and Plesionika martia) in the Bay of Antalya in the eastern Mediterranean. Data were collected from 27 valid hauls using the covered codend method. Selectivity parameters were obtained using the logistic equation with the maximum likelihood method and by taking into account the between‐haul variations. Results show that changing the codends from T0 to T90 increases the percentage of escapees for all four targeted shrimp species. According to species, a change in the mesh configuration significantly increases L50 by 7–14%. However, for the two commercially important red shrimp species (Aristaeomorpha foliacea and Aristeus antennatus), even the L50 values obtained in the T90 codend (23.3 mm) remain rather low for the release of sufficient numbers of immature specimens. First maturity sizes (FMS) for these two species are 38 and 30 mm, respectively; therefore, for their sustainable exploitation, additional management measures must be investigated including larger mesh sizes.

Assessment of the relative catch performance of hake, red mullet and striped red mullet in a modified trawl extension with T90 netting

“…T90 netting has interesting properties regarding species and size selection when used in codends. For instance, Deval et al (2016) tested codends with T90 meshes in four commercial shrimps of eastern Mediterranean trawl fisheries and showed that the percentage of escapes for all four species increases, as well as obtaining an increase in the L50. In Northern European fisheries, T90 codends have been subject to comprehensive studies that show a clear improvement in selectivity (Moderhak et al 1999) and in the quality of the fish marketed (Hansen 2004).…”

Modelling gear and fishers size selection for escapees, discards, and landings: a case study in Mediterranean trawl fisheries

“…Damalas & Vassilopoulou, 2013;Bellido et al, 2014) and selectivity parameters still remain low for some species (e.g. Sala et al, 2008 and references therein;Deval et al, 2016).…”

Predictive framework for codend size selection of brown shrimp (Crangon crangon) in the North Sea beam-trawl fishery

“…Therefore, the effect of mesh size on codend selectivity of brown shrimp is largely unknown and prevents the identification of optimal codend mesh size. In addition to mesh size, it has been demonstrated that altering codend mesh geometry using square mesh or T90 mesh (mesh orientation turned by 90°) can provide better selectivity for crustaceans than standard diamond-mesh codends [ 11 – 14 ]. Therefore, square-mesh codends or T90 codends may be alternative codend designs for the brown shrimp fishery.…”