Comparison of bycatch species captured during daytime and nighttime: preliminary results of longline experiments carried out in the Seychelles waters

Experiments were conducted aboard longline vessels operating in the Seychelles targeting swordfish and tuna. Experimental longlines fitted with hook timers and temperature depth recorders were used to identify differences in species composition, quantity and depth of catch between night sets using a shallow basket (swordfish target) and day sets using both shallow and deep baskets (tuna target). The majority of species were caught during day sets (75%). Lancetfish was the main bycatch species during daytime sets. Sharks were the most common nightime bycatch species, with blue and shortfin mako sharks being the predominant shark species. All marketable species were caught in the 150 m layer, marlins were never caught below 100 m. Sharks were caught below 150 m during both night and day sets. For other bycatch species, all were caught in depths less than 150 m during night sets. Daytime depth captures varied.