Billfish Resurrection: Scientists
Use Ingenuity, Technology
to Restore Population Size

For Florida, billfish are a boom to the economy, a joy for the angler, and an important target for researchers at the Rosenstiel School. Annually, sportfishing contributes approximately $2 billion to the Florida economy, and billfish, these tuna-like fish with the sword-like bills, are key to that revenue, despite their rapidly dwindling numbers. However, that’s only a part of the billfish’s value.

The Rosenstiel School’s Billfish Research Initiative is taking proactive measures to learn more about this economically and ecologically important group of fish that are as well known for their giant size and terrific fighting abilities when hooked as they are for being among the top predators in the oceanic food chain. Unfortunately, billfish, which encompass sailfish and blue, black, striped and white marlin, have diminished greatly, despite “no-take” laws along the U.S. eastern seaboard. Recent research suggests a 90 percent loss in the ocean’s top predatory fish. With billfish, the problem of conservation is exacerbated because they tend to be very mobile, thus they need protection all over the Atlantic, not just U.S. shores. Additionally, scientists and anglers actually know very little about their spawning, growth and behavior.

Starting small?
For more than 25 years, Rosenstiel researchers have been studying billfish in a variety of ways, but because these fish have such a large geographic range as adults, their life cycle is very dif- ficult to track. The school’s scientists take to the seas monthly with special high-tech nets designed to catch larval billfish specimens as indicators of reproductive activity. Researchers and their collaborators from other institutions use molecular DNA to identify species not even an inch long. They are also able to study larval stomach contents to understand billfish diet, and age and rapidity of growth from the ear bone or otolith. Otoliths bear rings much like a tree, with one new ring developing daily, allowing the scientists to determine larval age to the day. As researchers learn more about billfish growth, development and reproduction, they can determine what might help fish stocks to replenish—the ultimate goal of this kind of research.

Learning from the past
Over the past half-century, scientists and fishery managers have tagged more than 120,000 billfish, and data remains. Using statistically innovative ways to study the growth of billfish in the Atlantic Ocean with this data has proven fruitful. Mathematical modeling for white marlin was used in 2002 to evaluate whether these fish were overfished or endangered under the criteria established by the U.S. Magnusson-Stevens or Endangered Species acts. Additionally, by coupling this data with new high-tech tagging that helps track fish movement, the scientists continue to learn more about population fluctuations, the status of the current stock and realistic fishery management strategies.

Leading the way
Today, 15 Rosenstiel researchers are actively involved in a variety of billfish projects, and this work has not gone unnoticed. One of the school’s researchers chairs the billfish working group in the International Commission for the Conservation of Atlantic Tunas, the commission that advises governments about billfish management. Another scientist has led the development of a major Central America Billfish Agreement – the first in the region – which could serve as a basis for regional management of resources in the Eastern Pacific Ocean and to be signed by the presidents of the six affected countries. Rosenstiel billfish research expertise has been sought after in other countries too that share the economic and ecologic concerns that come with a declining billfish population.

Rosenstiel research continues to grow. What started as a $1.6 million endeavor has been leveraged into much, much more, with private donors “adopting a billfish” to subsidize the school’s high-tech tagging devices, and through federal funds. The way ahead seems clear– those interested in billfish want to find a way to increase their numbers, and Rosenstiel is working to make that happen.

For more information, contact:
Barbra Gonzalez, Communications Director
Rosenstiel School of Marine and Atmospheric Science
305.421.4704 • barbgo@rsmas.miami.edu

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