Although the research will focus specifically on blue marlin, the results of the study will also be useful to advance the understanding of the biology and habitat requirements of white marlin and sailfish.   Project research personnel are:  Nancy Brown-Peterson, Jim Franks, Bruce Comyns, Eric Hoffmayer and Don Johnson (all with the Gulf Coast Research Laboratory) and Jan McDowell (with the College of William and Mary, Virginia Institute of Marine Science).

The goal of the research is to document the timing and location of blue marlin spawning and identify possible nursery areas in the north-central Gulf.  This will be accomplished through investigations of adult and young (larval) specimens.

Owing to their pelagic lifestyle and highly migratory nature, only a small amount of biological data has been collected for blue marlin in the Gulf of Mexico and South Atlantic, and there is virtually no published scientific information on blue marlin biology and life history from the Gulf.   Scientific information for improving management of blue marlin resources is critically lacking.  This is particularly alarming in light of assessments that the Atlantic blue marlin is over-fished.

Recent collections of billfish larvae by the research team during studies of fishes that utilize Sargassum as habitat in the north-central gulf indicate the importance of the region as a billfish spawning area.   Species-specific knowledge of the distribution and abundance of billfish larvae is important because:  1) the presence of very young larvae is the only conclusive evidence that successful adult spawning activity has occurred at, or near, the waters of their collection; and 2) larval abundance may hold promise as an indicator of the number of spawning adults that produced them.

A multi-day research trip will be conducted each year in the noth-central Gulf to investigate larval blue marlin.  The 2005 trip will sample for the very young fish along the outer edges of the Loop Current as it (and its spin-off eddies) intrudes into the northern Gulf.  The 2006 trip will occur in an area of the northern Gulf that is bordered by the Mississippi River delta on the west and the upper reaches of the DeSoto Canyon on the east and extends seaward to depths approaching 6,000 ft.  These are regions of the Gulf where the research team has previously encountered Sargassum (weedlines and mats) and Oceanic fronts (color change, temperature breaks, etc.), and hypothe-size that such ecosystem features represent spawning and nursery habitat for billfishes in the northern Gulf.  Plankton nets and a variety of oceanographic equipment and remote (satellite) sensing imagery will be used during the offshore work.

Collections of blue marlin larve from the north central Gulf represents a way to simultaneously obtain information on billfish spawning and nursery habitat in the region, as well as to provide information on age and growth of the species.  Knowledge of the timing of female maturation and the age of larvae, coupled with data on ocean currents in locations where larvae are collected, is useful to "hindcast" probable spawning locations and times.   The identification of potential billfish spawning and nursery areas in the northern gulf is critical for the protection and conservation of the species.  Data from this study will provide a baseline for future assessments of the Gulf's blue marlin population for inclusion in updates of the Atlantic Billfish Management Plan.

The research team will also work collaboratively with the National Marine Fisheries Service (NMFS), Southeast Fisheries Science Center, Migratory Fisheries Biology Branch to assess archived gonad tissues collected at tournaments in recent years as well as fresh samples to be collected during 2005 and 2006.  This work will allow us to determine the maturity and spawning status of blue marlin caught during spring - fall months.

Results from this study will provide the first comprehensive analysis of blue marlin reproduction, spawning and nursery areas in the Gulf of Mexico.  We thank the National Marine Fisheries Service and the Gulf States Marine Fisheries Commission for the opportunity to conduct this important billfish research.  We are extremely appreciative of the strong support given our new research project by the Billfish Community.

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