Movement of blue marlin in the Gulf of Mexico

Blue marlin and other istiophorid billfishes are capable of traveling long distances, moving across ocean basins or between hemispheres. Because such movements can cross political boundaries, information on migration is crucial for coordinating international management and conservation of these species. The scale of movements and the habitat conditions of billfishes presents a difficult challenge to quantifying migratory pathways. Archival tags that record depth, temperature, and light intensity are a relatively new technology that offers the potential to reconstruct movements of fishes. Since 2003,, we have deployed 21 pop-up archival transmitting (PAT) tags on blue marlin during the summer spawning period in the Gulf of Mexico. To date, 18 PAT tags (30-180 day deployments) have reported, and the majority of pop-up locations have been within the Gulf of Mexico (82%) or in the Straits of Florida. Net movement per day of these blue marlin was low (~5 nautical miles per day) relative to rates reported for studies on blue marlin in the Atlantic Ocean ( in the Atlantic Ocean (e.g. Graves et al. 2002 [18 nm/day]; Kerstetter et al. 2003 [15-39 nm/day]), suggesting increased retention within the Gulf. Also, several blue marlin frequenting spawning grounds off Texas and Louisiana during the summer remained in the Gulf through the fall and winter.


	Figure 1. Deployment (circles) and pop-off (stars) locations for PAT tags placed on blue marlin in the Gulf of Mexico. Tags were programmed to pop-off at intervals ranging from 30-100 (green stars) to 180 days (red stars).


	Figure 2. Location estimates of a blue marlin (n = 20) tagged in the Gulf of Mexico from 2003-2005. Geo-locations (circles) were determined from pop-up archival tag data on light intensity, depth and temperature. The color of the circles indicates the time of season.

Copyright 2006, Pelagic Fisheries Conservation Program
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