Gamefish Prey on Sand Flats

Polychaetes are segmented worms that come in many body shapes. The many species can be divided into two general categories: tube dwellers and free-moving. Among the most recognizable tube dwellers are numerous filter-feeding species with large, bushy crowns that extend from the worm's tube or burrow. Christmas tree worms are typical of this group. The colorful crowns quickly retract into the tube if the worm senses danger. Weighted flies with marabou plumes are good imitations of these polychaetes. Free-moving polychaetes search for food along the bottom and may live in a tube, burrow into the sediment when seeking shelter, or simply live on the bottom. They are shaped as variations on the earthworm theme. Bonefish are the most notable gamefish that eat polychaetes with regularity.

A good number of crustacean species that occur in other habitats also live on sand flats. Those flats that border grass beds or mangroves receive an overflow of prey from these habitats; sand flats far removed from other habitats harbor a smaller list of prey species. Golden mantis shrimp dig burrows in the sand and emerge at night to feed. Mantis shrimp on sand flats are tan to closely match the color of the bottom. Snapping shrimp also inhabit sand flats. On hard sand bottoms, snapping shrimp shelter in pieces of shell or rubble, as will reef and pitho crabs. In softer-bottomed sand flats, snapping shrimp dig burrows. Juvenile common shrimp, up to three inches long, also burrow into soft sand, leaving a small hole for water exchange, and emerge at night to feed. Many species of swimming crabs also inhabit shallow sand flats and usually have excellent camouflage coloration.

Finally, numerous species of small fish are specially adapted to the sand flats, including a few species of small gobies that are either clear or blandly colored to match the sand bottom. The goldspot goby (Gnatholepis thompsoni), dash goby (Gobionellus saepepallens), and orangespotted goby (Nes longus), which makes itself comfortable in the burrows of snapping shrimp, are examples of gobies that live in burrows on sand flats. Pearly razorfish (Hemipteronotus novacula) and rosy razorfish (Hempiteronotus martinicensis) are members of the wrasse family (Labridae) and live on sand flats four feet deep or more. Razorfish hover above the bottom and dive into the sand when threatened. When living over sand, both species are pale in coloration.

Since so many of the prey that inhabit sand flats either live permanently underground or emerge at night to feed, it makes sense that gamefish that feed on sand flats have a good sense of smell. They use this sense of smell to find prey. Filter-feeding prey, like clams and some species of worms, draw water in one burrow opening, filter plankton and other food from the water, and then expel the water out another burrow opening. Gamefish that feed on these species can detect the outflow. Even organisms that don't filter feed aren't safe. Crabs, shrimp, and other gamefish prey have to pass water over their gills to obtain oxygen from the water, and this leaves a scent on the water that exits their gills. Gamefish are sometimes able to detect this water and track down unseen prey. Bonefish and permit are especially noted for this ability to smell their prey.

Strategies for Sand Flats

Since sand flats don't offer much in the way of shelter, their primary use by gamefish is as a feeding area. Granted, bonefish can get into such shallow water that they can escape sharks, dolphins, large barracuda, and other larger predators, but when they are that shallow, they can be targeted by ospreys and thus remain wary.

Because sand flats are so shallow, they can quickly become very warm in the heat of the summer sun and very cold after the passing of a cold front, in both cases making the flats inhospitable to gamefish. Given the wide open character of sand flats, gamefish are usually on the move, and the challenge for fly anglers is to interpret the flats to figure out the best places to intercept these traveling gamefish.

The biggest factor influencing the use of sand flats by gamefish is tides. It doesn't take much of a tidal change to influence the coming and going of gamefish. The well-known standard behavior for gamefish on sand flats is to follow the rising tide onto a flat and to reverse course and leave the flat with the dropping tide. Early in the incoming tide, the edges are the first places to look for fish coming onto the flat. As the tide rises, fish come over the edge and onto the flat, often using traditional routes to access the flat. At the very least, this behavior pattern means that even exploring a flat at low tide can bring rewards. If you happen upon fish concentrated along an edge, you're probably close to one of these traditional avenues of access. With a little searching, you'll probably find a small channel nearby that, even if very shallow, serves as the first access point to the flat on the rising tide. But before you get too excited, there's a catch-the locations of these avenues may change depending on the magnitude of the tide.

Spring tides occur with every new and full moon and cause higher-than-normal high tides and lower-than-normal low tides. The high spring tides flood more of the sand flats than at any other time in the tidal cycle, so gamefish tend to venture farther onto the flats in search of prey. And since more water moves onto and off the flats during spring tides, the currents are stronger. The combined higher water and stronger currents can cause a shift toward shallower locations as avenues of access for gamefish waiting to get onto the flats and exit avenues on the dropping tide. In contrast, neap tides occur at the first and last quarters of the moon and cause lower-than-normal high tides and higher-than-normal low tides. These tend to limit gamefish to smaller portions of the flat and to deeper access points.

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