Untitled

Abstract

This study investigated the selectivity of 90° turned meshes of 40 mm mesh size with 165 meshes around codend circumferences (40T1), 44 mm meshes size with 300 meshes around codend circumferences (44T1) and 44 mm mesh sizes with 150 meshes around codend circumferences (44T2). Experiments were carried out in the Kuşadası Bay of the Eastern Mediterranean, between 19 January and 29 March 2015 with commercial stern trawler. Selectivity data were collected using the covered codend method and analysed by means of a logistic equation with the maximum likelihood method. Individual hauls and mean selectivity parameter were estimated by using the CC2000 and EC-Modeller software, respectively. The mean 50% retention total length values (L50) and selection range (SR) were 12.7 cm and 2.3 cm for 40T1, 13.2 cm and 3.5 cm for 44T1 and 13.8 cm and 3.0 for 44T2, respectively. Significant differences were determined among the L50 values of the codends (between 40T1 and 44T2) (P<0.05). However, there are no statistical difference between the 40T1 and 44T1, 44T1 and 44T2 (P>0.05). On the other hand, L50 values of 40T1 and 44T1 are very close considered to the 13 cm length at first maturity size of the species.

No deleterious circumference effects for T90 codends in an Australian fish trawl targeting tiger flathead, Platycephalus richardsoni

“…Greater clarity on the effects of the circumference of T90 codends is required considering there are few studies and at least some species-specific effects. For example, doubling the circumference of T90 codends without lastridge ropes decreased size selection for Atlantic cod, Gadus morhua (Wienbeck et al, 2011;Veiga-Malta et al, 2019), but had no effect on bogue, Boop boops (Ilkyaz et al, 2017). Given the above, here we sought to test the hypothesis of no differences in the relative size and species selection of a conventional T0 codend and two new smaller-meshed, four-seam T90 codends at two circumferences and with shortened lastridge ropes when targeting tiger flathead in the CTS.…”