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- EXPERIÊNCIA PILOTO PARA AVALIAR A SOBREVIVÊNCIA DA CAVALA (Scomber colias) PÓS-SLIPPING NA PESCA DO CERCOPublication . Bandarra, Cidália; Silva, Alexandra; Instituto Português do Mar e da Atmosfera, I.P.Under the scope of Sardinha2020 Project, a pilot experiment was carried out to study the survival rate of chub mackerel (Scomber colias) after slipping. Slipping is the release of unwanted capture in purse seining, by lowering the head rope of the net and rolling over the fish back into the water. In Southwestern Portugal (Sesimbra), during the summer of 2020, the experiment was carried out using 2 small net pens (control and slipping treatment) moored in the open ocean, where fish slipped by a purse-seiner were monitored daily to evaluate the survival rate of chub mackerel. The control pen contained fish slipped in the initial moments of slipping (less crowding and density), and the slipping treatment contained fish aggregated at high densites towards the end of the operation. The results of this experiment revealed a high survival rate of chub mackerel on both net pens, reaching 94% in the slipping treatment and 97.7% in the control, after a 5 day trial period. For horse mackerel (Trachurus trachurus), unintentionally introduced inside the nets, this study revealed a reduced survival rate of 40% in the slipping treatment compared to 85% in the control net, suggesting that the slipping activity for this species could induce high motalities. In this study, individuals’ condition factor and caudal indexes, as well as physical conditions were evaluated during the experiment. It was verified that, for both species and for both control and slipping treatment, dead individuals, in general, presented more deterioration ofthese conditions, compared to the survivors. This work aims to evaluate the survival rate of chub mackerel and horse mackerel after purse seine slipping. This work is novel for both species, thus we expect this new knowledge, will be an important contribution to improve stock assessment of these species.