TPWD Billfish Research in the Western Gulf of Mexico
Randy Blankinship, Ecosystem Leader, Lower Laguna Madre
In the Gulf of Mexico, two hundred miles off the Texas coast, drifts an oasis of life amid a desert of open Ocean. A mat of sargassum holding hundreds of thousands of animals, many specialized to blend in with the plant, has within its intertwined food web, a small, voracious specimen showing little of the potential it has to become a giant. This early version of the grander (>1,000 lb) blue marlin it can become will swim through thousands of miles of ocean in its lifetime. It will also swim through a myriad of political jurisdictions, some with virtually no restrictions on fishing activity for its kind.
This tiny player in the ocean ecosystem is one of many young fish in the billfish family Istiophoridae that grow to become apex or top predators. As with their terrestrial counterparts, apex predators are less prolific than the relatively abundant prey species they pursue. The characteristics that make billfishes reproduce at lower rates also cause them to be intolerant of potentially high mortality levels from non-natural sources. For example, bycatch in commercial pelagic longlining activities inadvertently often includes several species of billfish.
In fact, the latest stock assessment for this group shows that blue marlin and white marlin are overfished throughout their range in the Atlantic Ocean and Gulf of Mexico. This range includes offshore waters of many coastal states and several countries and makes the role of international fishery management extremely important. The governing body that sets the levels of billfish harvest, both directed and incidental, is the International Convention for the Conservation of Atlantic Tunas (ICCAT). The United States is a member of ICCAT and negotiates with other countries in determining harvest levels. Such negotiations can only be successful if good scientific information is available to support good decision making.
The species of billfishes in the Gulf of Mexico (blue marlin, white marlin, sailfish and longbill spearfish) support an exciting sport fishery. Anglers spend an enormous amount of effort, time and money to experience the thrilling fight of one of the largest and most intensely energetic fish in existence. Yet, as popular as these fishes are, there is very little that is known about their life history -- where they reproduce, how many eggs are produced, how many larvae survive to adulthood, if variations of stocks exist within their range, how old they get and how fast they grow. This basic information is needed to allow proper fishery management measures to be made domestically and internationally and to enable sustainability throughout its range.
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