Cobia Fly Design: Hook Shape

A hooked up Cobia…but for how long?

Here’s a scenario:  You lay a beautiful cast in front of a cruising fish (snook, striper, cobia – the species doesn’t particularly matter).  Your fly lands in front of the fish, and as you strip once, then twice, the fish lights up and engulfs your fly.  You strip-strike (the sure fire way to sink a hook into the jaw of a tough-mouthed saltwater fish) and your line comes tight.  You let out a shout of excitement…and then your line goes limp.  The fly popped out.  So…what happened?

We’ve all been there, and had this happen, and while a number of possible causes exist, if this happens to you again and again using the same fly, I would look at the either the (1) sharpness of your hook, or (2) hook shape.  Once you’ve verified the sharpness of your hook (the usual culprit for lack of penetration) it’s time to consider hook shape.

Hook shape is a critical factor in fly design.  The shape of a hook, its size and weight, affects the profile of a fly, the way a fly floats or sinks, the way a fly casts, and ultimately, how a fly hooks a fish.  This summer, I had a very difficult time hooking cobia with a long shanked, 3/0 hook, used in a variety of fly patterns I had tied.  And often, when hooked, these fish would pull the hook free after a brief struggle.  Why?

1/0 Tiemco 600SP compared to a 3/0 Daiichi X452.  Note the penetration angle of the shorter shanked hook compared to the longer shanked hook.

Long shanked hooks are great for streamer flies.  They allow you to build large, bulky profiles – the kind of patterns that imitate large baitfish.  Their downside is the angle at which they can hook a fish.  When a fish eats your fly, it typically turns as it eats.  When this happens, the fish faces away from the angler, and the strip strike causes the fly to slide along the fish’s mouth, and out and around its jaws.  The shorter the shank, the better angle the hook has to penetrate into the fish’s mouth or jaws.  See the image above for an example (and imagine the hook trying to penetrate the red line as it is pulled along).

This winter, as I tie fly patterns for big fish (cobia, tuna, tarpon, large striped bass), I will be using shorter shanked hooks, like the Tiemco 600SP.  And I hope, when I come to tight to a nice fish next year, that hook stays put.

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