Dedicated to the advancement of
sustainable fisheries management

Satellite tagging of swordfish in the Southern California Bight

PIER researchers have been tagging swordfish since 2002 in an effort to better understand the movements, biology and ecology of swordfish in California waters.  The initial studies were based on recording the fine-scale movements (vertical and horizontal) of free-swimming swordfish and determine how they compare to other SCB pelagic species.  This work also investigated the environmental conditions (i.e., tide, moon phase, time of day, water temperature) that lead to basking behavior (when swordfish surface during the day and make themselves available to harpoon fishers).  These tagging efforts have also lead to the development and trial of alternative fishing gears such as deep-set buoy gear.  Fine-scale movement data provide researchers with the tools that are needed to assess gear selectivity and reduce bycatch.  Read more about PIER's swordfish tagging studies (Sepulveda et al., 2010).  

Additional studies that focus on documenting the muscle temperature of free-swimming swordfish are also underway at PIER.  These studies use modified satellite tags to record body temperature at depth.  Studies have shown that swordfish are capable of spending hours at depths well below the thermocline (300 to 500 m), where temperatures may be as low as 6ºC.   Given that swordfish regularly transition between the warm surface waters (night) and the extreme conditions experienced at depth (day), this study focuses on documenting the thermal conditions of the red, aerobic musculature.  The data from this work is also used in laboratory studies that test muscle performance over a range of temperatures.  

Swordfish basking at the surface just prior to being tagged
with a pop-off archival satellite transmitter (seen in the foreground)


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The Pfleger Institute of Environmental Research, PIER, is a non-profit 501(c)(3) organization based in Oceanside, California.