A (Hopefully) Simple Breakdown of Picking the Right Line Weight
Fly Line Weight by Sean O’Brien
There are a ton of variables that affect every aspect of fly fishing. Even if we just look at the different factors that go into picking a fly rod, we have to choose a reel, rod weight, length and material. And on top of all of that, you need to pick a fly line weight. But while a lot of the things listed will depend on personal style and preference, fly line weight nearly always boils down to one thing: what are you fishing for? Using the correct line weight enables you to use the appropriate flies, which will really help you dial in on your target species.
A good place to start when picking a line weight is looking at the recommendations on the side of your rod. However, this number is not absolute; it assumes perfect conditions, with no wind or other confounding variables. This is far from the reality of fly casting. Reality is coming around a small island in your kayak and getting whipped by gusts 10 miles per hour faster than they were on the leeward side of the island. Luckily, most fly rods can be loaded with line one size up or down from the stated weight, allowing fly fishermen to adapt their equipment without investing in a bunch of different rods.
Fly Line Weight
Here’s a brief explanation of what fly line weight should be used for which size and type of fish. You may need to go up a size if conditions are very windy or you need to throw a heavier fly.
1 to 3-Weight Line
This is for the smallest of the small, trout and panfish in tiny streams. These weights are considered highly specialized and not worth the investment unless you spend a lot of time fishing the very specific circumstances in which they’re optimal. If you are fishing those conditions, though, these lines can work great. They work great in tight quarters and cast well of of short rods, and in certain circumstances they can catch average to large sized trout in tiny streams.
Nearing the sweet spot for most, this line weight works well for pan fish, as well as trout up until the very largest fish. Best on mid to large sized streams where you will not need to cast very far .
This is the line weight for the all-around trout fisherman, as it will handle trout of every size, as well as small bass, and even tiny panfish, although they’re not as fun to catch on this rig.
This is a good all-purpose line as well, but it requires a tougher, stouter rig, eliminating the smaller panfish and trout, because the heavier line and gear kills the fun. This is the ideal weight for almost all bass and trout except the largest, and it’s also a great line for casting long-distance, depending on fly size.
This is the ideal line weight for larger bass, salmon and steelhead. It’s also useful for bigger trout in bigger bodies of water, and will provide a nice range of bigger fish options. Also a great line to cast for distance.
8-Weight Line and Up
These fly line weights are designated for the absolute monster freshwater species, the largest and most powerful fish, and saltwater species. This line weight is basically a no-go for anyone fishing freshwater and not chasing monster salmon.
Now that we’ve looked at different line weights and what fish they somewhat correspond with, we can dig deeper into the other factors affected by the weight of your fly line.
The most important is the size of the fly. This is determined once again by what fish you are going after. The target species will affect the weight of the fly, and mismatching the fly weight and the line weight can torpedo your chances of catching flish. If the fly is too heavy for your line – imagine you’re trying to cast a streamer on a 3-weight line – then its momentum will overpower the line, causing it to smack down on the water and spook the fish. On the other hand, a fly that’s too light will be difficult to cast accurately.
In general terms, most fly fishermen will be chasing trout, and using hook sizes between 10-16 with a 4-weight line. These are perfect, and allow the angler to target a the wide swath of fish species. On the other end of the spectrum, if you are chasing brook trout with streamers you may need to size up. So the best option is to determine what fish are going to be available, and base your gear on that. For the most part, though, a 4 or 5 fly line weight will let trout fishermen target fish in a wide range of sizes. For bass fishermen, a 5 or 6 fly line weight offers the same versatility.