Shoreline Rubble Flats

Other rubble flats lie close to or along the shoreline. It is common to come across small flats of coral rubble mixed with sand and seagrass as you drive around a Caribbean island. The land topography often continues into the water, so pay particular attention to flat stretches of land where the road passes close to the water. The road may provide shoreline access to a wadable shallow-water rubble flat.

Flats that are adjacent to busy roads or walkways are most productive at dawn and dusk, when traffic is low. However, fish that are resident in busy areas sometimes adjust to the activity and are not so easily spooked. That doesn't mean these fish will be easy to catch. They might not be easily spooked, but they might still be picky eaters or wary of poorly presented flies, or because the flats are so accessible, they might be heavily fished.

Other rubble flats are harder to find but can be worth the effort. Small flats off the beaten track will likely have less fishing pressure, so they may hold more fish. These isolated flats have provided me with great fishing over the years. If you have time before your trip, do your best to find a boater's map, or at least a topographical map. For U.S. waters, the United States Geological Survey (USGS) is a good place to start, as is the National Oceanographic and Atmospheric Administration (NOAA). The Internet is a valuable resource for both traditional maps and aerial photos that can reveal the locations of likely flats. Most islands have a government fisheries bureau, which is worth a phone call, though results are not guaranteed. I've found some very good maps in old fishing and sailing books. You don't need a map detailed enough for navigation, just one that shows you general patterns of inshore water depths and locations of reefs and shoals.

Fly-fishing strategies for fishing these flats will vary. On the narrow flats that parallel the shoreline, I prefer to slowly walk the shoreline searching for signs of fish. Walking on the shore provides a higher vantage point so I can see fish at a greater distance. I am also able to quickly move to a location down the shoreline should I see activity such as a tailing fish. Don't be surprised to see fish right up against the shoreline, especially at high tide or at dawn or dusk. If you don't see fish after a pass along the shoreline, you may want to wade the middle of the flat. If this strategy doesn't work, wade to the outer edge of the flat and try casting into deeper water. Such blind-casting might result in a nice jack, snapper, barracuda, or even the occasional small tarpon. If you don't see fish on your first visit to a flat, try again at a different time of day or a different point in the tidal cycle. I know of a few flats where large schools of bonefish cruise the rubble zone in the last hour and a half of the incoming tide but are completely absent at other points in the tidal cycle. Still other flats have feeding fish at dawn and dusk, seemingly regardless of the tide.

Gamefish Prey of Rubble Flats

The blend of rubble, seagrass, and scattered corals supports a diverse assortment of prey species. Rubble flats with seagrass mixed in have the same suite of prey as seagrass habitats, while rubble flats without seagrass harbor a subset of seagrass prey species. In addition, the many crevices among the rubble are good hiding places for an assortment of other prey species.

Chief among them are small members of the spider crab family (Majidae). These crabs feed along the bottom and scurry for the undersides of shells and rubble when chased. Green reef crab (Mithrax sculptus) and tan reef crab (Mithrax coryphe), and to a lesser extent gray pitho crab (Pitho aculeata) and pitho crab (Pitho mirabilis), top the list and are eaten by bonefish and permit.

The carapaces of reef crabs are triangular with rounded edges. The pitho crabs are teardrop-shaped, with their eyes at the narrow end of the teardrop. All four species listed here grow to one inch but are often smaller. The abundance of each species varies among locations, but the green reef crab is usually the most common in shallow rubble flats mixed with seagrass.

When choosing a fly to imitate spider crabs, your choice of color can be simplified to the basics: dark green, brown, or tan, depending on the species. The pitho and gray pitho crabs are tan to gray in color, the green reef crab is dark green, and the tan reef crab is tan.

Porcelain crabs (family Porcellanidae) also inhabit shallow rubble flats. The lined porcelain crab (Petrolisthes galathinus) is especially abundant on finger corals growing on mixed rubble and seagrass flats. The lined porcelain crab is small, at two-thirds of an inch, and medium green. It has an oval carapace and oversize, flattened claws.

When fishing flies that imitate these small crabs, the action you give the fly should be minimal. All species of walking crabs remain close to shelter, whether under a rock, among seagrass blades or algae, or burrowing into the bottom, and they don't scurry over long stretches of open bottom when chased. You may want to give your fly a couple twitches to get the attention of the bonefish or permit, and then let it sit still.

Mantis shrimp live in holes among the rubble or shells and are similar in appearance to the praying mantis land insect, thus the name. When living among sparse seagrass with coral rubble or open sand bottom, the golden mantis (Pseudosquilla ciliata) is tan in coloration. The rock mantis (Gonodactylus oerstedii) is typically dark green or black but also varies to match its habitat. It is mostly found among rock and coral crevices. Mantis shrimp usually don't venture far from their burrows and are most active at night. When chased, their defense posture is to turn and face their adversaries while retreating backward toward their burrows. While these species of mantis shrimp can reach four inches, usually only the smaller ones are eaten by bonefish and permit.

Sand Flats

Sand flats are pretty simple habitats. There's not much structure to shelter prey or to hold gamefish, yet sand flats can be great places to fish for bonefish, permit, snapper, and a host of other species because they present an easy habitat for gamefish to feed. The more complex the shelter of the habitat, the harder it is for predators to find and catch prey. So although open sand bottoms don't host as many prey as seagrass, a gamefish's chance of finding and catching prey are much higher.

Spend some time wading sand flats, and you'll soon conclude that not all sand flats are created equal. The type of open bottom reveals the typical wave and current conditions an area experiences and can give you a good idea of whether it is a good feeding area for bonefish. Sandy areas with waves or ridges are frequently exposed to waves or currents that cause shifting sands, which tend to have fewer prey organisms than more stable sediments. Stable sediments also tend to be softer because of mixed mud and detritus due in part to the activities of the resident animals, which makes these bottoms more hospitable to more organisms. Sand bottoms occur in areas with more wave or current energy than mud bottoms, or in locations far removed from a source of soft, fine sediments that make muddy bottoms. Rivers, streams, estuaries, or lagoons with currents that might carry sediments are potential sources of soft-bottom sediments.

The survival strategies of species that live in areas with stable sand bottoms provide clues to their presence. Many of the species that live on sand flats dig burrows, and they show themselves by the presence of these burrows. These species may filter feed, eat detritus that is delivered by tides, or emerge from their burrows to feed on the surrounding bottom. Clams bury themselves in the sand and extend tubular siphons to the surface in order to filter plankton and other food from the water. Some worm burrows are as big around as a penny, and some species of worms and shrimp discharge large amounts of sand out of their burrows. Such clues indicate that you are on a "live" sand flat that supports gamefish prey.

Finding a live flat is an essential first step to finding gamefish. Most gamefish try to get away with as little travel as possible in their search for a meal, so once they've found a good place to feed, they'll use the area repeatedly. After you've found a live flat, you can set about figuring out when and how gamefish take advantage of the food source.

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