Satellite tagging of swordfish (Xiphias gladius) in the Southern California Bight

PIER Research Staff:: Chugey Sepulveda, Ph.D.
Scott Aalbers, M.S.
Captain Tom Fullam “Cowboy”

Project objective

To record the vertical and horizontal movements of swordfish in the Southern California Bight using pop-off satellite transmitters (P-SATs).

Background

The swordfish is a valuable commercial resource targeted world-wide. In California, there are two primary fisheries that target swordfish, the traditional harpoon fishery (that targets swordfish when they bask at the surface) and the pelagic drift-gillnet fishery.

Although highly-selective (close to zero by-catch), the harpoon fishery is often not as efficient as the more destructive methods (long-line and drift-gillnet) commonly used to harvest swordfish around the globe. One goal of the present study is to analyze the swordfish movement data so that we better understand how environmental conditions affect basking rates and times. These analyses have the promise of increasing the efficiency of this traditional and highly-selective fishing method.

The drift-gillnet fishery has been routinely ridiculed as a non-selective fishery that results in high by-catch rates. In an attempt to reduce by-catch and increase gear specificity for swordfish, the vertical movement data will be analyzed as to determine depths in which swordfish segregate from other SCB pelagics. These data will be compared with other pelagic species that co-exist in the bight (i.e., pelagic sharks, turtles, marine mammals) in an overall attempt to identify which portion of the water column should reflect the highest swordfish take and simultaneously result in the lowest by-catch.

Swordfish tagging