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The Hawaii Bonefish Tagging Project

From 'Current Line', a Hawaii Dept. of Land and Natural Resources newsletter and reproduced with permission from the author

By Bruce S. Anderson, PhD
The sound of the thick fly line cutting through the water as the fish rips out a hundred yards of backing is sweet music to the ears of every saltwater fly fisherman. You either love the flats–and you check the tides and your calendar everyday to see if you can sneak away for a few hours–or you can’t understand why anyone in their right mind would waste so much of their time doing something with so few tangible rewards. If you’ve read this far, you’re probably in the former group.

There are probably less than two dozen hard-core fly fishermen in Hawaii. Veteran saltwater fly fishermen who call Hawaii home, Dick Gushman, Jim Romig, Kelvin Taketa, Ron Lum and others travel all over the world “chasing” bones. Enthusiastic newcomers to the sport, like me, only dream about the Seychelles, New Caledonia, Palmyra Island and some of the other exotic destinations they have fished in their travels. One thing we all share in common is that we would rather be walking the flats anywhere than doing anything–well, almost anything else.

Some refer to them as “grey ghosts” of the flats. O’io, as they are known to most fishermen in Hawaii, are indeed grey or sometimes light green in appearance. They have shiny, silver scales that reflect the color of the bottom and the fish’s surroundings. of a bonefish Without bright sunlight to cast a shadow, they are difficult to spot even if you are looking directly at them with polarized glasses.

Next to ulua, papio (jack crevalle) and other jacks, bonefish are the most sought after inshore game fish for recreational fishermen in Hawaii. Despite their popularity, little is known about their distribution, movement, or growth rates. Surprisingly, little is known about bonefish behavior worldwide. The fact that bonefish are not a commercially important food fish is one of the reasons. From this standpoint, the species is grossly undervalued as a resource.

What we know and don’t know
Only the basic life cycle of bonefish has been described in the many books and articles on the subject. They travel in loose schools, route out shrimp, shellfish, crabs, and fish from the bottom for food, and spawn offshore. Eggs hatch into a ribbon-like larvae that metamorphose into fish-like form at about two inches; then, the fish move inshore. Mature fish are commonly found feeding on inshore, shallow flats, usually over mud, coral and grass and, occasionally, over white sand. Otherwise, little is known about bonefish movements or reproductive behavior. Most fishermen do not know that there are two species of bonefish in Hawaiian waters, glossodonta, also called “Roundjaw” bonefish, and Albula neoguinaica, called “Sharpjaw” bonefish. While the two have been unequivocally established as discrete species using biochemical markers and examining their internal skeletal structures, it is challenging to distinguish them by appearance. The only visible anatomical feature that differentiates the species is the shape of their lower jaw. The Roundjaw species generally has a broadly-rounded lower jaw. The Sharpjaw species have an angular lower jaw which is more or less pointed.

These two species of bonefish evolved in Hawaiian waters over a period of over 30 million years. They were an important fish in Hawaiian culture. However, there is little historical information that would allow a comparison of fish populations over time and there is no historical data on recreational fishing catches in Hawaii. Only anecdotal reports from fishermen suggest the numbers of bonefish have decreased dramatically over the past two decades, presumably because of over fishing and habitat loss. We do know the number of pounds of commercial bonefish landed has decreased dramatically, from 70,000-100,000 pounds per year in the late 1940’s to less than 10,000 pounds per year since 1985.

What we need to know
We have some information, but we need to know a lot more about bonefish in Hawaii if we are going to develop appropriate resource management and protection programs. We need to know about their distribution and movement to know where conservation programs would be most effective. We also need to know their growth rates to determine stock maturity and reproduction rates. This is basic information needed for any conservation program intended to preserve and protect bonefish or any other species. It is also critical that we collect this information in Hawaii. Hawaii is very different from the Gulf of Mexico and the Caribbean where other studies are underway. The geographic isolation of the individual Hawaiian Islands and long distances and deep channels between the islands provides a very different habitat than other areas where bonefish are found. In the Caribbean, for example, bonefish have been known to travel for over fifty miles. However, this is in an area where fish could swim hundreds of miles along coastlines with similar habitat without encountering substantial barriers. The deep ocean channels between the Hawaiian Islands pose a formidable barrier and dramatically curtail bonefish movement. We will likely discover that we have much more in common with other Pacific Islands, such as Palmyra Atoll, where the Nature Conservancy has also begun a bonefish tagging project. The information we collect from this project should have relevancy elsewhere in the Pacific.

Filling the gaps
Several months ago, a group of fishermen and fisheries management experts, including Dr. Gordon Grau and Dr. Richard Brock got together to talk about ways to fill in the gaps of what we don’t know about bonefish in Hawaii. With financial support from the University of Hawaii Sea Grant College Program, the O’io Tagging Project was born. It’s purpose is to collect information to characterize the bonefish resource to support appropriate resource management and conservation programs.

Finally, dependent on the amount of information fishermen provide, it is hoped that this study will begin to define the “catch-andrelease effort” for the fishery around Oahu. At present, there is no data available to describe fishery dynamics, the hours spent fishing, the size of the catch, or the effects of exploitation because the catches of recreational fishermen are not reported.

Tagging
The bonefish caught by those participating in the project will be tagged utilizing anchor tags and methods previously developed for the “Ulua Tagging Project” and adapted to bonefish. Annette Tagawa and Clay Tam, Education Specialists with the Division of Aquatic Resources of the Department of Land and Natural Resources, have been invaluable in providing technical guidance in this regard.

Essentially, the tagging method involves inserting a thin, polyethylene dart tag, commonly called a “spaghetti” tag, in the area high on the back of the fish. A plastic barb on the head of the dart tag keeps the tag from pulling out of the fish after it is pushed through the muscle and between the bones just below the dorsal fin. The tag has an identifying number and telephone number to call to report information when the fish is captured. After the fish is tagged, the tag number, the species, the fork length (measured from the tip of the mouth to the fork of the tail), the date and time of capture and the location is recorded and reported. Upon recapture, the same information is recorded and reported.

A dedicated telephone line has been setup at Nervous Waters Fly Fishers in Kaimuki to receive calls and record this important information. To date, 12 fishermen, including professional fly fishermen Clay Yee and Kevin Faucheux at Nervous Water Fly Fishers, have volunteered to participate in this project. Because of limited supplies and equipment that could be purchased with the grant funds, a maximum of 20 participants fishermen will be recruited the first year. Our target is to tag 1000 fish over this period. It is hoped that funds will be available to continue the project and expand the number of participants over the next few years. All fishermen, of course, are encouraged to report the capture of tagged fish. Data on the exact location fish are caught will be kept confidential; only summary statistics will be reported for areas such as Kaiaka Bay, Mamala Bay, Kaneohe Bay, etc. This will allow detailed tracking of movement without giving away your favorite fishing spots!

What we expect to learn It is anticipated that within a year or so, we will have some limited information on bonefish movement (in miles), dispersion, and, possibly, mixing patterns by species.

Preliminary information on growth from tagging and recapture data may also be available, depending on recapture rates. As more fish are tagged, we can, of course, expect more to be recaptured. We plan to develop accurate and verified length and weight curves to encourage the release of fish that are caught. Using data on the date and time of capture, it may also be possible to retroactively determine environmental factors, such as tides, phases of the moon, and perhaps other factors that may influence bonefish movements and behavior.

All fishermen who participate in this program whether tagging or in recovery of tagged bonefish will be given information pertaining to that particular fish. When the fish is first caught, this will include confirmation of the date caught, the location captured, and the fork length of the fish. Upon recapture, information provided will include the date, location, and fork length of the fish and a history of its previous captures, including the days free, distance traveled (in miles) and growth (in inches) between captures.


(Note: Due to lack of funding the tagging project was terminated in 2006 but was revived by the Oceanic Institute in 2007 and is currently compiling statistics submitted by anglers throughout the state.)