Understanding fly fishing hook size isn’t the sexiest topic around, but your hook is your link to the fish and is closely related to the size of your flies. Pretty sexy stuff!  Well, maybe that’s just me thinking.  Most fly anglers’ exposure to fly fishing hooks size is when they learn a certain fly fishing hook size that is most effective for catching certain fish species. “What size of flies do you need?”…”oh, size 8.” In many cases, this works just fine, but in others it is downright useless. I remember an engineering student once telling me the story of his experience with understanding physics. He learned one or two rules about physics and thought he really understood everything there is to know about physics. Then he learned ten more rules and understood that all of those rules affect the first rules he had learned. Like with the rules of physics, fly fishing hook size is based off of a ton of different features that truly determine the “size” of your hook, and when you change your thinking on fly fishing hook size, you can hook and land way more fish.  Remember this…fly fishing hook size is not a number on the package.  Before you read further, take the little test below in the photo.

GUESS THE SIZE OF THESE HOOKS BASED OFF OF THE NUMBER ON THE PACKAGE. LEFT HOOK = #2/0.

FLY FISHING HOOK SIZE: THE BASICS

Most people understand fly fishing hook size through years of fly fishing experience. You get a general knowledge of hook size when you’ve seen dozens of them. You learn quickly that the smallest flies have a bigger number and that the biggest ones have a small number. They range from the minute 32 to the large 1.

However, this changes when you move past 1. Now, the larger the size, the larger the hook. You now add a zero, for example, 1/0, which is bigger than a 1, 2 or 32. This system gives you the puny 32 to the shark-sized 20/0. This system is really not reliable at all, however, and the system for designating fly fishing hook size has been in constant change over the centuries.

With modern fly tying hooks, there is really no universal standard hook size to begin with. For example, we can’t start with a hook that is a size #10 and that is 10mm long, because not all brands have the same #10 designation. They are close, but they are not exact. The present system is reliable to a certain extent, for example, a #12 hook will almost always be “larger” than a #22. In reality, very infrequently is this helpful when you are tying or getting information on fly fishing hook size. If you are a beginner and you are confused about the hook sized, consult someone who ties flies and ask them what the most common models are for a given fly pattern. This will help you to become familiar with general sizes. However, pay attention to all of the descriptions on the package. Once you understand what these are saying, you don’t have to worry about these numbers anymore, as long as the overall proportions are correct for the natural that you are trying to imitate, for example.

The numbers on fishing hook packages, used to designate fly fishing hook size, can at times be useful once you become familiar with most of the styles and brands of hooks, but you should not pay much attention to them if you want to choose the best hook for the job. Sometimes the number will be fine with what you want, but at times, it will be nowhere near. Think outside the box and don’t be restricted by a number. If you find a hook that is a 2/0 that is the perfect hook for flies normally tied as #4s, then use it if it’s right. The huge amount of variables with fly fishing hook size give you this freedom and you should become familiar with what these variables are.

FLY FISHING HOOK SIZE: FEATURES THAT CHANGE YOUR HOOK SIZE

SHANK LENGTH

A 6 STREAMER HOOK AND AN 8/0 BIG GAME HOOK CAN HAVE THE SAME SHANK LENGTH.

When you think about hook size, you may think of shank length more than anything. The shank of the hook allows you to create longer and more substantial flies by tying the materials over the available room on the hook. The proportion of the natural that you are trying to imitate usually determines how long of a shank you want. The problem is that hooks can come in various shank lengths even with the same number designation. For example, a #8 hook can be #8 2x long, 3x short, 4x long. The x system normally means that the hook is sized up one hook size (this is not universal). For example, a #10 1x long hook, has a shank that is approximately the size of a #8 “normal” hooks. However, to make matters worse, the “original” “normal” hook shank length varies slightly from brand to brand. Putting aside this brand variance, the x system means that you can literally have a #6 6x hook that can be used to tie a fly as equally as big as a #8/0 big game hook. There are ten steps in between these two hooks (6, 4, 2, 1, 1/0, 2/0, 3/0, 4/0, 5/0, 6/0, 7/0, 8/0), but the fly would be the exact same size if measured with a ruler, i.e., the shanks are nearly equal in size. This is an extreme example, but this fact exists at all levels of fly size, and it gets really important when you use a few hooks of different shank sizes for one particular fly. Of course, shank size is not the only feature to think about, it’s the combination of all the features (just like the physics rules) that make up the overall fly fishing hook size.

GAP SIZE AND BEND STYLE

SAME SHANK LENGTH, DIFFERENT HOOK GAPS, AND DIFFERENT HOOK SIZE NUMBERS.

The gap size of fly fishing hooks acts as an equalizer of sorts. You still have variance in the hook gap though. This variance is usually marked off by “extra wide gap” or “wide gap” on the packages of the hooks you are buying. There are also dozens of hook bend styles. These can make a difference in the actual hook size but often contribute more in other areas such as hook penetration. You need to work with the shank and gap size to come up with the hook that you need. The primary reason you need to do this is because the ratio of these two can make a huge difference in hooking and landing fish. A hook with a long shank and a small gap will probably have difficulty hooking fish because the materials will obstruct the hook point. This same hook will also have difficulty keeping fish hooked because the long shank allows the hook to act as a lever inside of the fish’s mouth. For this reason, you want a hook shank-to-gap ratio that is more equal. You can find hooks that come in all sorts of hook ratios and shapes. It’s better to find the right ratio than it is to buy a hook that says a certain hook size number on the package. The down side with this approach is that you need to examine the hooks yourself rather than blindly following the advice of someone else.

There is one other main feature that shapes fly fishing hook size, hook thickness. Hook thickness is technically a part of fly fishing hook size, although it isn’t as noticeable when compared to shank and gap size. The x system also applies to hook thickness as well, for example, 2x heavy/thick. NI general, hook thickness is very important. There are three main reasons to pay attention to hook thickness. 1) The smaller the diameter, the easier a hook penetrates and thus goes into the fish’s mouth. The best example is a mosquito or a tick’s proboscis, which you most often can’t feel when it penetrates your skin. Depth has something to do with this as well, but do you want a knife blade or a syringe needle taking blood from you? The smaller needle penetrates much more easily—and painlessly. There is more at play with hook penetration than the diameter of your hook, but this is a huge factor nonetheless. 2) The thicker the diameter of a similar material the faster it sinks. If you are fishing in shallow water, you don’t usually want a fly that sinks like a rock unless you are presenting the fly from the bottom. 3) The thicker the hook, all things being equal, the more pressure you can put on a fish when playing it. The practicality of this should be somewhat obvious.

When it’s all said and done, fly fishing hook size comes down to the specifics of a given hook and brand. The best way to figure out if a hook is perfect for your fly is to gain experience yourself by examining various hooks. You can also call on experts and guides to give you recommendations. You might examine a few recipes of fly patterns that guides post on their websites, or you can email them and ask what specific hooks they like and in what sizes. Even with this approach, you can still do better than guides in some instances. Take what they tell you, and improve on or follow their advice for a particular body of water.

THE MOSQUITO HOOK HAS A GREAT SHANK TO GAP RATIO.

Details in most things make the difference between good anglers and anglers who probably don’t land or hook a lot of fish. If you care about catching fish, then you should abandon the idea of hook size (as designated by a number) as a way to choose your hook for fly pattern. The finished size of the fly itself should always be your number one concern for a given fly pattern when choosing a hook size. Once you have that general size and proportion, you can feel free to play around with the features of the hook that determine fly fishing hook size. If a guide tells you that you need size 2/0 tarpon flies for your trip, you should ask him how long the fly should be. If he says, “2.5 inches”, then tie your fly on whatever hook you want, as long as the finished fly is 2.5” and it gives you the qualities you want for presenting, hooking, and landing fish. If you use a size 4/0, but the fly is balanced well with a great hook, then all the better. No fish is going to be checking to see if your fly is a 3/0 or a 1/0, so you shouldn’t either. Use the hook that gives you the most advantages while maintaining the proper proportion for the natural food source and situation you’re fishing. When all is said and done don’t forget that fly fishing and fly fishing hook size isn’t physics. It’s much more important!

HOW DID YOU DO WITH YOUR GUESSES?