New Studies Reveal critical Data Regarding Migration Routes And Spawning Patterns
Fishermen are optimists, there's just no other way to describe us. Every time we step onto a boat or wade a shallow flat, there is a renewed sense of hope that it will be a great day of fishing. Dedicated fishermen also tend to be adventurous, whether exploring new waters or simply excited with new tactics and techniques.
Part of our passion stems from the constant search for new information about the game fish we go such lengths to target. It should come as no surprise that understanding the intricacies of their behavior, feeding patterns and migration routes will only improve our ability to find and catch more fish.
Bonefish are highly prized game fish due to their incredible sporting abilities, but unlike commercially valuable species, bonefish have received little attention from the scientific community. Until recently our knowledge of their migration and spawning patterns, mortality rates and lifetime growth potential has been very limited. While scientists have started to uncover important information, much work is still needed to support effective management decisions and ensure long-term sustainability. Unfortunately, the shallow flats that are essential to the well being of bonefish populations are often in the near vicinity of environmentally degrading coastal development projects.
Two of the more vexing questions from guides, anglers, and scientists have been about bonefish migration patterns and spawning activities. In other words, are the fish we encounter on our favorite flat always the same fish? Are there areas we should identify for protection to ensure bonefish can safely spawn and recruit to provide future generations of gray ghosts?
The conventional wisdom has always been that bonefish are homebodies. But until recently, this was never tested. What we have learned and continue to discover will surprise you.
More than 10-years ago, Jerry Ault and his graduate students at the University of Miami began a tagging program for bonefish in the Florida Keys. Prior to the initiation of this project no one had ever examined bonefish migration patterns. It was unclear whether they had small home ranges, or were creatures suffering from wanderlust. Over the projected period Jerry and his students, working closely with local guides, tagged more than 8,500 bonefish with conventional dart tags. So far, anglers have recaptured over 350 tagged bonefish, which is right on par with recapture rates from the majority of tagging programs.
The initial data from the Florida Keys tagging study revealed a wide range of movement patterns. What we found is that the majority of bonefish stick close to home for extended periods in perhaps favored habitats or feeding grounds, with approximately 42% recaptured at or near the tagging location and approximately 70% recaptured within 5-miles of the tagging location. So to some extent, as you are getting to know a bonefish flat, the fish are also getting to know you.
However, don't let these short distance movements fool you. We've also experimented with surgically implanted ultrasonic tags and the results are impressive. So far, the acoustic telemetry tagging studies have shown that bonefish will stay in one area for more than 60 days, and then make abrupt and significant moves. Interestingly, these movement patterns tend to correspond with spawning season.
Some bonefish are more long-distance champions and have been recaptured great distances from the original tagging location. About 20 of the bonefish tagged in Biscayne Bay and the Upper Keys were recaptured in the Lower Keys. In addition, two fish that were tagged in the Upper Keys were recaptured by anglers fishing on Andros Island in The Bahamas. This is a distance of more than 125-miles and one that required a swim across the deep and fast-moving waters of the Gulf Stream. The question now is whether this Florida-Bahamas movement is a regular occurrence that links the two seemingly disparate fisheries.
While only time will tell, the results shed light on a few things. First, it's important to protect habitats and locations where we find and fish for bonefish because these are likely the fish's home waters. But it's also important to protect large, continuous tracts of interconnected near-shore habitats because bonefish do undertake long-distance movements.
To test whether the findings in the Florida Keys hold true elsewhere, Bonefish & Tarpon Trust is also sponsoring bonefish tagging in The Bahamas and Belize. Will these bonefish act the same and undertake long-distance movements, or will they prefer to stay close to home? So far, results in these tropical locations are following similar patterns of what we learned in the Keys—that most bonefish seem to remain in small areas, but there's also a good bit of long-distance movement. In the Abacos, where over 700 bonefish have been tagged, all of the recaptured fish have been caught within a few miles of where they were tagged. Remarkably, one fish was caught in the exact same spot it had been tagged a year earlier.
In contrast, a study by Vanessa Haley in Andros that took place during spawning season, in which bonefish were implanted with ultrasonic tags, revealed that some bonefish undertook migrations of 50-miles to reach spawning grounds, returning days later to the areas where they were tagged. We can only hypothesize that the long-distance movements in the Keys were the result of the same type of spawning migration. We've just started tagging bonefish in Belize, and it will be interesting to find if their movement patterns are the same. Over the course of the next few years we should accumulate even more information on bonefish migration patterns.
Until recently, we didn't know where or when bonefish spawned. Recent research that BTT helped fund sheds some light on the subject. At the Cape Eleuthera Institute in The Bahamas, Andy Danylchuk and his colleagues used ultrasonic tags to discover that bonefish spawn on full and new moons between October and May. They also discovered that bonefish spawn at night in offshore waters. Near dawn, the bonefish returned to the shallows. Since the work at Cape Eleuthera Institute, BTT has funded projects in Andros and is currently funding research in the Abacos to identify spawning locations. We're also working to determine exactly how far bonefish travel to reach a spawning site, whether each population has a single spawning location, and whether bonefish return to the same spawning site year after year.
With a wealth of information being uncovered, anglers can only benefit. Knowing the range of movement is important for effective management. From an angler's perspective, we are eventually going to run out of new hot-spots to travel to in pursuit of bonefish. Already there are locations where the bonefishing is not as good as it once was because of habitat degradation. Protection of a particular flat, for example, although important, might be insufficient if bonefish regularly move among many flats that are miles apart. If bonefish move across international boundaries, then countries that share bonefish populations are going to have to cooperate to ensure their fisheries remain healthy. Since it appears that many of the long-distance movements by bonefish are related to spawning, it's now obvious that spawning locations need to be identified and protected, because each location likely supports a bonefish population that is spread over a large area. If you would like to help promote conservation through science, visit tarbone.org and click on the research tab.
Aaron Adams is Director of Operations for Bonefish & Tarpon Trust and a senior scientist at Mote Marine Laboratory. Jerry Ault is a Professor of Fisheries and Director of the Bonefish & Tarpon Conservation Research Center. Michael Larkin is a Ph.D. candidate at the University of Miami's Rosenstiel School of Marine and Atmospheric Science. Rosenstiel School of Marine and Atmospheric Science.