Study

Predictive models and comparison of the selectivity of standard (T0) and turned mesh (T90) codends for three species in the Eastern Mediterranean

  • Published source details Tokaç A., Herrmann B., Aydın C., Kaykaç H., Ünlüler A. & Gökçe G. (2014) Predictive models and comparison of the selectivity of standard (T0) and turned mesh (T90) codends for three species in the Eastern Mediterranean. Fisheries Research, 150, 76-88

Actions

This study is summarised as evidence for the following.

Action Category

Rotate the orientation of diamond mesh in a trawl net

Action Link
Marine Fish Conservation

Use a larger mesh size

Action Link
Marine Fish Conservation
  1. Rotate the orientation of diamond mesh in a trawl net

    A replicated, controlled study of an area of seabed in a coastal bay in the Aegean Sea, off Turkey (Tokaç et al. 2014) found that rotating the direction of diamond mesh in a trawl codend by 90° increased the size selectivity of red mullet Mullus barbatus and common pandora Pagellus erythrinus, but not annular sea bream Diplodus annularis, compared to the standard diamond mesh direction. The length at which red mullet and common pandora had a 50% chance of escape was larger in codends with turned diamond mesh of three mesh sizes compared to standard diamond mesh (mullet, turned: 12–18 cm, standard: 9–15 cm; pandora, turned: 10–13 cm, standard: 9–11 cm), and there was no difference for annular sea bream at all mesh sizes (9–12 cm). Trials were done by research vessel in Izmir Bay during several periods between December to May. Three bottom trawl codends with diamond mesh turned by 90° were tested against two codends of standard diamond mesh orientation. A total of 61 valid deployments of 30 min were made: 13–17 hauls of turned diamond mesh codends of each of 40, 44 and 50 mm mesh size; and 10–11 standard diamond mesh codends, each of 40 mm and 50 mm mesh size. Al codends were attached to the same trawl net. Codend catches were sorted by species and fish length recorded. The year the study took place was not reported.

    (Summarised by: Rosslyn McIntyre)

  2. Use a larger mesh size

    A replicated, controlled study (year not stated) in an area of seabed in a coastal bay in the Aegean Sea, Turkey (Tokac et al. 2014) found that larger codend mesh sizes, both diamond and turned (90°) meshes, in a bottom trawl net improved the size selectivity of red mullet Mullus barbatus, common pandora Pagellus erythrinus and annular sea bream Diplodus annularis compared to smaller mesh codends. For both the standard diamond mesh and diamond mesh turned by 90°, the average length at which fish had a 50% chance of escape was greater as mesh size increased: for mullet (50 mm: 15–18 cm, 44 mm: 11–15 cm, 40 mm: 9–12 cm), pandora (50 mm: 15 cm, 44 mm: 11–13 cm, 40 mm: 9–10 cm) and bream (50 mm: 12 cm, 44 mm: 10 cm, 40 mm: 9 cm). In addition, the lengths of 50% escape were higher in the turned diamond mesh compared to the standard diamond for mullet and pandora, and similar for bream. Data were collected from 61 trawl deployments (30 min) in Izmir Bay in December-May (years unspecified), using five different experimental codends: 50 mm diamond mesh (10 hauls), 44 mm mesh, standard (10 hauls) and turned 90° diamond mesh (17 hauls), and 40 mm mesh, standard (11 hauls) and turned diamond (13 hauls). Small mesh (24 mm) covers attached over each codend collected fish escaping through the meshes. The species and lengths of all fish in the codends and covers were recorded.

    (Summarised by: Rosslyn McIntyre)

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