Development and Trial of Deep-set Buoy Gear for Swordfish, Xiphias gladius, in the Southern California Bight
Fishery interactions with nontarget species (including U.S. federally protected sea turtles and marine mammals) have severely impacted U.S. west coast swordfish, Xiphias gladius, fisheries and have hindered the development of alternative domestic operations. This study used swordfish depth distribution data to aid in the design of deep-set fishing gear to target swordfish in the Southern California Bight (SCB). To minimize nontarget interactions, the deep-set gear was designed to fish at depths between 270 and 320 m during day-light hours. The deep-set buoy gear (DSBG) configuration consisted of a vertical mainline (2.2 mm monofilament) affixed with a 4 kg weight and two 8 m gangions (1.8 mm monofilament), each rigged with an 18/0 circle hook and baited with mackerel, Scomber spp., or squid, Illex spp., or Dosidicus gigas. Surface floatation included a 36 cm diameter (21 kg) longline fl oat and two smaller (3 kg) strike indicator floats. Experimental fishing trials were conducted using ten individual pieces of DSBG deployed simultaneously. Soak duration was maintained at 4 h/set and the gear was hauled immediately upon detection of a strike. Gear trials were conducted within the SCB from August to January of the 2011 and 2012 swordfish seasons from both research and cooperative fishing vessels. From 54 sets (4,320 hook-hours), 14 swordfish were captured without any interactions with bycatch/nontarget species of concern (i.e., sea turtles and marine mammals). Additional species captured during the trials included: bigeye thresher sharks, Alopias superciliosus (7); opah, Lampris guttatus (2); blue sharks, Prionace glauca (2); and common thresher shark, Alopias vulpinus (1). These data suggest that deep-set fishing operations can selectively target swordfish during the day within the SCB and provide a basis for further testing using commercial applications.