Intermediate Fly Line: When to Use

Intermediate fly lines are considered a jack-of-all-trades for many fly fishermen. They can be used in a wide variety of conditions and is often the go-to line for those that have to only choose one. 

Whether fishing from the boat or the shore, let's find out when to use intermediate fly lines. Let's talk about what it is.

The Basics of Intermediates

The intermediate fly line allows anglers to fish in the upper, shallower portion of the water column. Typically, it is used for a few feet below the surface because it sinks at a slow rate and can help you target fish as they swim at varying depths. 

Now, there are no specific standards set for the sinking rate of an intermediate fly line. They generally have a 1 inch per second (IPS) sink rate although some lines are at 1.25 IPS while others can reach 2 IPS. It’s best to ask the manufacturer of the line that you’re interested in on the specific details. 

There are two main kinds of intermediate fly lines – monofilament and braided. They are often transparent and while they may have their own specific uses, they both perform better if dipped in water beforehand. 

The mono lines are more translucent once it's in the water and can take on a slimy appearance once they’re wet. This has earned it the moniker of a slime line or glass line. However, monofilament intermediates are prone to line memory and need to be stretched periodically. 

Braided intermediate lines, on the other hand, are softer, less transparent, and are less prone to line memory. They can come in semi-transparent variants and even camouflage designs to make them less visible to fish. They are also more sensitive to detecting bites. 

While intermediate fly lines can reach the bottom if you retrieve them slowly, it's generally best to only let them sink into the top few feet of water. This is where calculating the sink rate is essential. For example, an intermediate fly line with a sink rate of 1 IPS will sink 10 inches in 10 seconds. If it has a 2 IPS on the other hand, it will sink 20 inches in 10 seconds, and so forth.

Intermediate lines also offer a smoother transition between your backcast and forward stroke. Catching fish often happens on the retrieve as the line and lure move upward to the surface, so you’ll need to adjust your retrieve speed proportionate to the depth that you’re targeting. This helps anglers maintain their lines at a specific range of depth below the surface while still actively retrieving. If you pull an intermediate line too quickly, you’ll technically only be fishing inches below the surface.

Due to the sinking times, it’s not advisable to use intermediate fly lines while drifting. By the time it reaches your desired depth, you may have already drifted right over your fly or out of the optimal range. Therefore, they’re best used anchored, wading, or from the shore. Intermediate lines are best for shallower waters, particularly around weed beds.

Despite being optimal for choppy waters because it can keep your line below the surface better, intermediates aren’t recommended for waters with a current. The line cannot be mended in its standard form, but if using a sink-tip line that has a short intermediate tip, it can offer better line control. This is will cause most of the line to float, thereby offering an easier chance to mend it.

Unlike floating lines, intermediate fly lines can be retrieved from a more “friendly” range of a few feet to a few inches below the surface. They’re best used with artificial lures, both weighted and unweighted, and are effective when partnered with buzzers, nymphs, and drop shots.

Washing Line Method

They can be used with the washing line method as well. For those who aren’t familiar, this is a multi-fly technique that lets you fish a dry fly with several nymphs suspended just below the surface of the water. Using an intermediate fly line in this scenario lets you go a little bit deeper, but you’ll need a lead fly that floats fairly well to support the sinking weight so that it doesn’t submerge. 

A foam arsed blob (FAB) is your best bet, along with a couple of nymphs or buzzers. Once you cast out, strip any slack so the line sinks. The lead should remain buoyant while the droppers sink down below. This setup is commonly used for brook trout and cutthroat trout during hatches, especially when they’re “top-and-tailing” while feeding on emerging insects. If the fish takes one of the droppers, the lead fly will suddenly vanish or the line might lock and straighten, so get ready for a show as the fish can be quite explosive on the take. 

You can fish with intermediates as you would with dry flies, but you’ll typically want to cast to a prospective area, allowing the droppers to sink and waiting for them to bite. 

The Middle and the First

Intermediates are versatile, but if you need more depth, you can fish a heavier fly with a short leader to increase the sink rate. A leader around 4 to 6 feet long is more than enough for any scenario. Do take note that because of the intermediate’s slower sink rate, you can’t immediately go for a second cast. You’ll need to strip the line first before gearing up for a second go. This forces you to be accurate with your first cast, which a lot of anglers actually prefer. 

With all the possible applications, it's no wonder that the intermediate fly line is a common choice for most anglers. Whether it's surf fishing for tarpon or casting beneath bridges for snook, this fly line can hit a sweet spot in the water column that other lines can't. 

So, the next time you explore a lake or go fish from the shore, you may want to bring an intermediate fly line along. You just might be surprised at what it can do!