Incredible tenacity and an inherently "spooky" nature make this flats fish the most commonly sought-after saltwater game fish on fly. This ghost of the flats has the uncanny ability to appear and disappear almost at will and tends to flee at the slightest disturbance. Stalking bones on the flats becomes every bit as much a hunt as it is fishing. As with any hunt, it's best to know as much as you can about the prey, including its habitat and habits.
Habitat and Behavior
When you're fishing in water only a foot deep, tide and time of day can have a dramatic effect on water temperature, and these factors can change a barren flat to a productive one almost instantly.
According to fisheries biologist Derke Snodgrass, like many flats fish, bones prefer water ranging in temperature from the mid-70s to the mid-80s. "If the water gets too much warmer, they stay in deeper channels," says Snodgrass. An incoming tide can suddenly warm cooler water or cool warmer water. Subsequently, during cooler weather the middle of a sunny day presents a good time to look for bones on the flats, while early morning and late evening provide better fishing in the heat of summer.
Tides are critical to bonefish in another way, too. According to Snodgrass, it appears that bones spend more time on large, expansive flats during the rising tides. On deeper flats, or flats adjacent to deep water, however, bonefish may be present regardless of tidal flow. The best time to fish large shallow flats is during the higher stages of the tide when the fish can safely swim onto the flat and feed throughout the slack tidal period. If the tide is low or falling, look for drop-offs over which the warm water will recede because bonefish will be following the warm water. Keep in mind that large flats that remain too shallow for bones to feed for most of the month will almost always draw bonefish when extra-strong tides associated with the full and new moon flood the area.
Studies indicate that regardless of the habitat, bones feed mostly on mollusks and crustaceans like pistol and mantis shrimp, shrimp eels, toadfish and small crabs found in the sand or on the bottom. Studies by the Florida Marine Research Institute suggest large bonefish, 17 inches and up, eat more shrimp, toadfish and crabs than smaller bones. The major difference in these prey items within different environments is coloration. As you might expect, on grassy flats like those in the Keys, the prey items are darker, while over hard or sandy-bottomed flats the prey items tend to be lighter in color.