Wahoo are some of the most amazing predators in all of the world’s oceans. The shear speed in which they strike coupled with razor sharp teeth and beautiful coloration results in a superb game fish that ranks high on every anglers’ hit list. Utilizing catch statistics and tagging data, scientists have been able to precisely document the migration routes of sailfish, kingfish, tarpon and dolphin. Unfortunately, little is known about the almighty wahoo. One thing we do know for certain is that these fierce predators stage along deep ledges of The Bahamas during the winter, but where do they go from there? To get the inside scoop, we contacted Tim Theisen of Florida Atlantic University. Along with researchers from the University of Hawaii’s Marine Lab and the University of Iowa’s Genetics Program, Theisen recently completed a study on the population genetic structure of wahoo. The results were very intriguing and sparked interest among biologists, marine fisheries managers, and dedicated anglers.
FSF: How did you become involved with wahoo research?
Theisen: While attending FAU for my Ph.D. I was particularly interested in identifying patterns of genetic distribution within fish species, and then examining how these patterns may relate to historical events, reproductive behavior, and contemporary movements of individuals. Dr. John Baldwin started a wahoo research project, and as an avid angler I jumped at the opportunity to work on the project. Once I received my degree I stayed involved because there were still questions that had not been answered. Because of a wahoo’s similarities to other pelagic game fish there is a wealth of knowledge we can learn about blue water species as a group that is sometimes difficult to learn when you are studying populations that aren’t as healthy as they once were.
Anglers may be under the assumption that a large group of fish are holding in a particular area, while in reality it’s a conveyor belt of fish moving through.
FSF: What type of research was initially conducted?
Theisen: We researched genetics by extracting and comparing DNA from wahoo captured around the world. We uncovered that wahoo are widely distributed, yet there was no distinguishable population structure that we could detect. Scientifically this is referred to as a heterogeneous distribution. Even looking at genetics we could not distinguish between a fish caught in Bermuda and a fish caught in Hawaii.
FSF: What else can you tell us about wahoo?
Theisen: While closely related to kingfish and other mackerel, in terms of behavior and where it hunts and lives wahoo are more similar to billfish and tuna. We know that marlin and tuna have the ability to thermoregulate, which greatly expands their niche. In addition, most billfish have the limited ability to heat their brain and eye muscles, enabling them to search deeper depths when hunting. Wahoo don’t have these abilities—as far as we know—yet one thing we do know is that they are equipped with specialized gills for oxygen uptake.
FSF: How do you uncover this information?
Theisen: I’m currently studying the movement patterns of mature wahoo by deploying pop-up satellite archival tags (PSATs). These tags store reasonable estimates of a fish’s latitude and longitude, depth, and temperature preferences on an almost continual basis over a three month period. While PSAT tags are very expensive, the information revealed is of great value to scientists and anglers who target wahoo. By combining data from several PSAT tags with tidal, lunar, and weather information it may be possible to improve one’s ability to determine where and when a particular species of game fish will be found feeding in the future. We also use conventional streamer tags to get secondary data. With streamer tags we can find out where a fish was captured and recaptured, and if you can believe the original size estimate you can measure its growth over time. Streamer tags don’t tell us a whole lot, but any catch data is useful.
FSF: What have you learned from tagging?
Theisen: We immediately noticed that a wahoo’s migration pattern isn’t as simple as one would think. Last year I tagged two fish in October off West End, Grand Bahama, and two fish in February off Lake Worth Inlet. Conventional wisdom has it that the fish tagged in October should be moving towards The Bahamas, however this was not the case. All of the fish moved north. Two traveled as far as Savannah, another was recaptured offshore of the Chesapeake and another offshore Cape May. One thing they all had in common was that they stayed in the warm water of the Gulf Stream. Ultimately, pelagic species such as wahoo are on a constant hunt for food. A conventional streamer tag that was placed on a wahoo in Hawaii was recovered off Midway Island—a distance of more than 1,100-miles. This clearly demonstrates that wahoo have the ability to travel long distances. They don’t seem to care how far they go, as long as they are following food.
FSF: What’s holding researchers back from learning more?
Theisen: Wahoo are arguably the best-tasting fish, which makes conventional tagging programs difficult because no one wants to release them. Even if you convince anglers to tag-and-release wahoo, the way these fish are targeted they usually don’t come to the boat in great condition. It’s also difficult to get funding to support our research, with most grants going to species that have greater impacts on society. You’re either a commercially valued fish or cuddly tropical fish, and wahoo is neither of those.
FSF: So little is still known about their migration patterns?
Theisen: Anecdotal evidence from recreational anglers’ catch data tells us that in Florida juvenile wahoo tend to move inshore during summer months, with mature wahoo leaving the area altogether in the summer. Large fish inhabit The Bahamas during the winter and are less common during the summer, although they can be encountered on any given day of the year. One thing tagging can tell us is if the fish are transient or showing up as a migratory pattern and hanging out for an entire season. Unfortunately, we don’t have the answers just yet. Anglers may be under the assumption that a large group of fish are holding in a particular area, while in reality it’s a conveyor belt of fish moving through.
So there you have it. While there’s still a lot to learn about wahoo, there has already been a wealth of information uncovered about this great game fish. Stay tuned for more information, as in the not so distant future even more will be revealed.