Is Cuba Contributing to Florida Keys Bonefish Crash?

In a report in these pages last fall, you may recall, I mentioned this possible connection almost as an aside. The possible connection emanates from the fact that bonefish spawn in the open ocean, where their larvae are picked up by currents and swept along. The predominant current along the northwestern coast of Cuba flows northward toward the Keys. It is commonly understood that the Keys receive lobster larvae and young groupers from “upstream” via the Gulf Stream and other Caribbean/Gulf of Mexico currents. If bonefish larvae use the same conduits, any adverse impact on the upstream sources of young bonefish could be felt in Florida.

This basic idea moved beyond speculation when it was determined last fall that the bonefishery along Cuba’s northwestern shore has indeed been hammered in recent years. Apparently, 10 to 15 years ago an industrial-scale netting operation commenced, including the use of one-mile-wide seine nets dragged across the flats between two boats. Local guides informed Bonefish & Tarpon Trust representatives that the netting occurred proximate to bonefish spawning aggregation sites and nearly wiped out the local population. The effort lasted until a year or two ago, when not enough fish remained to sustain the commercial program. This period coincides with the dramatic decline in Florida Keys bonefish. Was this coincidence or cause and effect? The possible existence of cause and effect (i.e., a connection) elevates the speculation to a hypothesis to be tested and scrutinized.

For the lay person, the connection theory appears attractive. It is established fact that bonefish travel between Florida and Andros Island over 100 miles to the east—across the Gulf Stream. It is also established fact that millions of spiny lobster larvae ride currents from the Caribbean, Yucatan, and maybe Cuba to the Keys, where the larvae mature and grow. Without this “recruitment” from upstream, the Florida Keys would have only a sparse lobster population. Studies show that fish, such as groupers, also use the currents to end up in Florida and off the coast of North Carolina hundreds of miles to the north. Finally, many Cuban refugee rafts also end up in the Keys. It doesn’t take much imagination to surmise that bonefish larvae, or young, might travel 90 miles from Cuba to the Keys.

Various studies of Keys-area currents indicate the existence of connections. For example, one scientific study of larval transport concluded that “observed and modeled data suggest the upper Keys is a point of onshore larval transport [from upstream Caribbean sources] via the inshore meandering of the Florida Current, and the lower Keys to Dry Tortugas region a point of [larval] retention through wind-driven onshore countercurrents and eddy recirculation.” (Fisheries Oceanography, Vol. 11, Aug. 2002.) Other studies conclude there are extensive connections among the Yucatan Peninsula, Cuba, the Gulf of Mexico, and the Keys.

But it should be noted that scientists are waving caution flags. Species that remain in the larval stage for only a short time (e.g., 10 to 15 days) are homebodies and likely not connected by current. Such species include Queen Conch and some snappers that do not reach the Keys from upstream. At the other end of the spectrum, lobster larvae live six months or more, allowing them to be widely distributed. Bonefish are in between, remaining in the larval stage for a bit over 50 days. Also, very close analysis of the Gulf Stream and Florida Current shows that deeper currents can be very different from the surface flows. For example, 100 feet down in the Gulf Stream there are currents that move fish larvae inshore to the reefs rather than pushing them north on the Stream. The fact that bonefish spawn in deep water might put the larvae at the mercy of these deeper countercurrents rather than the readily apparent surface currents

Bonefish & Tarpon Trust, which discovered the existence of the Cuba netting operation, has approved (and is funding) a new set of studies regarding the connection theory. Bonefish from Cuba and the Keys, as well as other Caribbean populations, will be subjected to new DNA testing. The first objective is to determine which DNA markers would establish connections among these populations and then the focus will turn to looking closely for those markers. If matches are found, it will be empirical evidence that the connection exists. Conversely, the absence of matching markers would indicate the populations are separate. Dr. Aaron Adams, BTT’s director of operations, emphasizes that the inquiry will be looking broadly at possible connections among Belize, Mexico, Cuba, and the Keys.

Similar connection studies often examine ear bones (otoliths), which can provide even more detailed information. However, since bonefish are usually subject to catch-and-release angling, the initial focus will be on DNA, which can be collected with minor fin clips, allowing the fish to be released and survive.

This summer a new project to locate young Keys bonefish will kick off. Presently, bonefish in the Keys are all two to three years old or older; no one has found juvenile Albula vulpes in Florida recently, although years ago guides used to see and catch young-of-the-year sixto eight-inch bones. BTT is conducting a broader search for young bonefish to help determine where the fish come from and the habitat they need to survive and grow. The problem in Florida may be that young bonefish arrive here but don’t survive because of habitat or water-quality problems or both. In recent years, a summer fishery for two- to three-pound bonefish has developed west of Key West, while Middle and Upper Keys bonefish populations continue to slide. That might signal that homegrown water-quality or habitat problems are the culprits—not the Cubans.

Fortunately, there is some continuing good news on the Keys (and Florida Bay) habitat front. The first wave of Everglades restoration projects have been built and are starting to operate, causing measurable and evident improvements in the Bay. Congress recently authorized four more restoration projects including the C-111 Spreader Canal, phase two (which benefits northeast Florida Bay and Biscayne Bay coastal wetlands). A healthier Biscayne Bay likely means more bonefish for the Upper Keys).

There is likely no single explanation or single solution for what ails Keys bonefish. It is assuredly going to take a lot of additional research to unlock the mysteries of what happened to this great game fish in the Keys and what is needed to get it back on the road to recovery. I’m guessing cooperation with Cuba is going to be increasingly important in coming years.—Bill Horn.

Don Causey Note: The netting operation Horn describes above took place far away from the celebrated Cayo Coco fishing area of northeast Cuba, and even farther away from the famed fishing areas on the south coast of Cuba, such as Queens Garden Archipelago, Cayo Largo, Isla de la Juventud, and Bay of Pigs. As regards Bonefish & Tarpon Trust, if you bonefish or chase tarpon, or just dream of doing so some day, you need to join the organization. You can do so on their website at: www.bonefishtarpontrust.org.