Circle-Hook Requirement Should Reduce Release Mortality for Cabo Billfish
By Mike Mazur
For the first time in the 10-year history of the Los Cabos Billfish Tournament, crews will be required to use non-offset circle hooks on all their live- and dead-bait rigs. That’s music to the ears of billfish off Land’s End.
It’s a fact: Circle hooks reduce mortality. 
In the May 2008 issue of Marlin magazine, Dr. John Graves, chair of the Virginia Institute of Marine Science, College of William and Mary, reported on two circle-hook studies he has conducted over the past six years. These studies were done on white marlin, but it’s a reasonable assumption that similar results would arise among released sailfish and striped, blue and black marlin off Cabo.
Graves’ initial study (see Figure 1) placed pop-up satellite archival tags (PSATs) in 40 white marlin caught between 2002 and 2003 off the U.S. mid-Atlantic coast and La Guaira Bank, Venezuela. Half those fish were caught on J hooks, the other half on circle hooks. The results? Seven of the 20 marlin caught on J hooks died within a 10-day tagging period, while no mortalities were recorded among the 20 fish caught on circle hooks.
A second study (see Figure 2) compared three models of commonly used circle hooks. Sixty PSATs — 20 per circle-hook model — were deployed in white marlin off the U.S. mid-Atlantic, Mexico and Venezuela. Usable data was registered from 59 of those tags. After a 10-day tagging period, an amazing 58 fish had survived!
These impressive results have led scientists to estimate that the exclusive use of circle hooks could result in 1,300 to 2,600 more white marlin surviving release each year in the U.S. recreational fishery alone.
Who knows how many more released billfish will survive off Cabo because of circle hooks. But thanks to the efforts of tournament organizers, their future is suddenly much brighter.
