RUBBLE FLATS and sand flats provide great opportunities for sight-fishing in the tropics. Neither habitat has a lot of structure, but both support sufficient numbers of prey to provide good feeding areas for bonefish, permit, snapper, and a host of other gamefish that venture into these shallow habitats to feed at high tide. Sand flats have been well covered in numerous books on flats fishing, so most of the discussion here is limited to prey of this habitat. Rubble flats, on the other hand, have been shortchanged in the fishing literature, so this section delves a bit deeper.

Rubble Flats of the Backreef

A backreef rubble flat is well protected from waves by a shallow flat. The seagrass growing along the rubble (foreground) and the open rubble bottom (center) probably indicate differences in wave energy during high-wave periods. Note the barracuda (center of picture).

Rubble flats are my favorite shallow-water habitats of Caribbean islands because they are home to permit. Even if you don't find permit, you may still find bonefish, jacks, barracuda, triggerfish, snapper, small sharks, and other gamefish on backreef rubble flats. The typical rubble flat lies behind a coral reef, offshore of which is deeper water. Seagrass and algae eventually take hold in the backreef and spread into the lagoon, which results in a further slowing of currents and more deposition of debris and sand. In some spots, small colonies of finger coral grow among the seagrass. When everything works out just right, a shallow rubble flat results.

Water depth is the primary factor affecting whether you will find gamefish on a backreef rubble flat. The two factors most influencing the water depth are tides and waves.

Tides

Tidal range in the Caribbean is generally small, the water level changing a foot or less through a normal tidal cycle. Still, gamefish respond to even minor tidal fluctuations. On shallow flats, gamefish may be completely absent during low tide but may venture far onto the flat in search of food at high tide. Many times I've seen this occur even though I've been unable to detect a difference in water depth between tides.

In general, fishing the backreef flats is best from the latter half of the incoming tide through the first hour or so of the outgoing tide. In addition, backreef flats that hold good water throughout the tidal cycle are great places to search for fish at dawn and dusk, regardless of tides. I am not a big fan of early mornings, but when living in the Caribbean, I frequently dragged myself out of bed before dawn to walk my favorite backreef flat at first light.

Waves

Waves are almost constantly assaulting the outer edge of the reef that protects backreef rubble flats. And as on sandy beaches, the surf pushes water onto the reef. Some of this water is deflected seaward by the coral reef, but some of the water passes over or around the reef and onto the flat. If the reef is relatively deep or the tide is particularly high, a considerable amount of water can push over the reef and create an appreciable current on the flat. In addition, the remnants of larger waves that crashed onto the reef can maintain some of their form and roll across the flat. Both the wave-induced current and the small waves continuing across the flat can dislodge prey hiding among the rubble.

In contrast, other reefs and flats are shallow, so under normal conditions, there is little wave energy that continues over the reef onto the flat. These shallow, more protected rubble flats offer a different challenge in presenting a fly to a feeding permit or bonefish. The shallow water means the fish may be more wary of a fly hitting the water, and since the fly can quickly become lost in the crevices among the rubble, you must cast it closer to the fish to make sure it gets noticed.

Whether or not the reef and flat are shallow, extended periods with strong surf can increase the water depth more than tides. The constant surf will actually push more water onto the flat than can escape back to sea through cuts and channels in the reef, which can result in higher-than-normal water depths for the duration of the strong surf. Gamefish will take advantage of these high-water periods just as if the high water were due to an extended high tide. An added bonus to the near constant flushing of new water from the incoming waves is that backreef rubble flats rarely get as warm as nearby shallows with less water flow, so they can be good places to fish when other flats are too warm for permit and bonefish.

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