Crab Flies for Big Bonefish

crab flies

I was recently asked, “What is your favorite pattern for casting to tailing bonefish?”

Without hesitation, I said “A crab pattern.” I like crabs for two reasons: they have a high calorie content, and crabs are almost always present in shallow water. Bonefish are opportunistic feeders and are able to take advantage of the great diversity of prey they encounter on the flats. In a study in the Florida Keys, for example, more than 130 species of prey were recorded in the stomachs of 385 bonefish.

But such a large list of prey isn’t very helpful to an angler trying to select the best flies for a fishing trip. Fortunately, although bonefish have a diverse diet, a few types of prey are consistently in the top five, making fly selection easier. Chief among the top types of prey are crabs.

In my experience, crabs are almost always present in the shallowest water. As the tide
turns to flood, hungry bonefish push into the skinniest flats in search of small crabs that are feeding in relative safety. In fact, I have watched bonefish slither across shallow flats, their bodies half exposed, to feed on small crabs. But crabs are present in all of the habitats used by bonefish, so every fly box should have a selection of crab patterns.

There are far too many kinds of crabs to worry about imitating a particular species, the way a trout angler would. Instead, it makes sense to focus on the three main groups of crabs that are eaten by bonefish, and then use flies that mimic the general characteristics of these groups. Within each group, we can focus on the similarities among the species to minimize the number of flies we need to imitate them.

Swimming crabs (family Portunidae), mud crabs (family Xanthidae), and spider crabs (family Majidae) are the most common small crabs eaten by bonefish. Crabs from all three families are well camouflaged in their surroundings—whether they’re green in areas of seagrass, mixed tan and green in areas where coral rubble is mixed with seagrass, or tan or brown on shallow mangrove flats. In addition, although the maximum sizes of these crabs vary among species, the sizes most often eaten by bonefish tend to be similar—typically the size of a quarter or smaller.

The greatest differences among these families of crabs involve their behavior, which influences pattern and presentation. Species of swimming crabs are all similar in shape. They can be voracious predators and scavengers, and always seem to be on the move. Their color varies from the olive green of blue crabs, to tan with eyespots for some tropical species, to light tan on the sand flats. Swimming crabs use their paddle-like rearmost legs to swim through the water, and they will swim rapidly sideways to escape a pursuing bonefish. Their move of last resort is to dive to the bottom and either duck under cover, such as a rock, or bury in the sand.

Because swimming crabs swim sideways, they tuck in their legs and claw on the leading side of their body, and let their legs dangle behind them on the trailing side of the body—this is the most hydrodynamically efficient orientation. The Legless Merkin (size 4) fly pattern is designed to mimic this orientation, with a generalized body trailed by a barred tail that mimics the trailing legs. This fly lands lightly, so you can cast it very near the fish. Once it’s on the water, allow the fly to drop to the bottom, and then move it with short, quick strips. Once a bonefish sees the fly, change your retrieve to a long, slow strip.

Mud crabs and spider crabs are both walking species. They lack the rear, paddlelike
leg that allows swimming crabs to move through the water. Therefore, mud and spider crabs maintain a close association with hiding places on the bottom. Mud crabs, when chased, hide at the bases of grass blades, burrow into the soft bottom, or scurry under a rock or shell. Spider crabs are especially abundant among rocks and shells in seagrass beds and sand flats, and on rubble flats. These species feed along the bottom and scurry for the underside of shells and rocks when chased.

The sizes generally eaten by bonefish range from about 1/4 inch to 1-1/4 inch across, with most crabs measuring between 1/2 and 3/4 of an inch. These groups of crabs were the inspiration for Norman’s Crab (size 6), a small pattern that lands lightly on the water and is best fished by leaving it still on the bottom. The movement of the rabbit fur and rubber legs implies a mud or spider crab busily foraging on the bottom, unaware of the approaching bonefish.

If they run out of other options, all crabs will turn to face the approaching bonefish, in an attempt to ward it off by snapping with their claws, all the while moving their legs as they search for a hiding place. Similarly, swimming crabs diving for the bottom can be a blur of motion. The commotion of waving claws and rapidly moving legs was the inspiration for the marabou and rubber legs of the Bastard Crab (size 4). I’ve had great success when using this pattern for both cruising and feeding fish in knee-deep or deeper water. When you cast it close enough for them to see the fly drop, the fish will often east the fly as it drops to the bottom. If you feel like the fly needs some action, a quick strip followed by a freefall works well, with the fly typically eaten on the freefall.

Adams Crab Selection
2 each pattern: 1 light, 1 dark
Item #6P8T | $15.95
to order, call 1-800-548-9548