Several marine studies have shown that for a few days, actually twice a month, from November until May, schools of bonefish gather around sunset, then swim together away from shore. Once in deep waters, as if on a crowded dance floor, the bonefish get busy loving on each other. Even as romantic as the moon is to us, so the full and new moon draw throngs of bonefish to the drop-off at the edge of the reef, where water depths exceed 1,000 feet.
It was in April of this year that our own guides here at East End Lodge identified a pre-spawning aggregation of bonefish. We contacted Bonefish & Tarpon Trust and over a four-day period during the full moon phase they found schools of 500 to 3,000 pre-spawning bonefish located in a small deep protected bay.
Starting in mid-afternoon, the school swirls like a tornado in water 30 feet deep. Bonefish are normally found on the sea bottom in shallow waters, but at this stage some of the school rush up and porpoise, gulping air as they break the surface. Bumping against each other in this pre-spawning behavior, they must avoid sharks, barracuda, birds and Cubera snappers stalking them.
Pre-spawning bonefish typically stage for several days, and gather in pre-spawning schools in protected bays before swimming offshore at dusk. After swimming offshore, they descend to approximately 150-200 feet, and stay there for an hour or two before quickly ascending. Now suspended in deep waters, these usually shallow-water swimmers suddenly rush upward. B&TT believes it is during this ascent that bonefish eject their eggs and sperm into the water, where fertilization occurs, and the eggs hatch about a day later. There is something about the pressure of the descent/ascent to depth that is important for the spawning success. At that point the spawn is over and the fish quickly move back into shallower water.
This shows the importance of protecting the shallow bays that bonefish use for pre-spawning AND the nearby offshore deep areas they need to spawn.
It also gives us a little insight on why bonefish are such a rough and tough adversary for us fishermen. Not only do they risk being eaten by a host of predators to leave the flats and spawn offshore, but face a greater challenge as millions of fertilized eggs left behind in the deep sea, must drift to begin a two-month larval stage that will result in a new baby bonefish settlement somewhere nearby to begin the cycle over again.