Escape de juveniles de merluza (Merluccius hubbsi) en las redes de arrastre de fondo, mediante la aplicación del dispositivo de selectividad DEJUPA con diferentes distancias entre varillas, utilizando un diseño especial de copo re retencion en la grilla.
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This work reports on the inter rod distance in a single sorting grid adapted for the escape of hake juveniles. A good performance of the device was reported due to the DEJUPA trials carried out in April 1997. In may 1998 a new survey with DEJUPA was carrie out with 30 mm, 33 mm, and 40 mm separation distance bars, in order to optimise the escape of the species at first length maturity (35 cm). Selectivity curves with maximum likelihood method were obtained for each inter rod distance being the length at 50. (L50) 29, 32 and 37 respectively. A weighd lineal regression (Feasible General Squares Model) between L50 and inter rod distance was fitted from each L50 estimated variance. An estimation of 37 mm inter rod distance for L50=35 cm total length was obtained by inverse regression. In this opportunity a special design for the retention codend was attached to the outlets of the DEJUPA in order to retain the escape of fishes. With the aim of retaining the whole fish distribution a blinded codend was used in the bottom trawl net, therefore every haul in this experience became a complete experiment.