All About Blue Lining | How to Use Maps & Apps to Discover Trout Streams

It's never been easier to find trout in remote places.

One of the benefits of blue lining: it's usually just you on the water. | Photo by Jasper Taback

Trout anglers are drawn to blue lining for several reasons – maybe you love native fish, perhaps you need some time alone, or maybe your go-to river is inundated with visiting fly fishers. However you get into it, it’s tough to stop once you get started. Here are the best ways to find the trout fishing gems that appear as razor-thin lines on a topo map. 

Topographic Maps

These days, many states offer online, interactive topo maps through their fish and wildlife departments. Zoom in on the area you’re interested in exploring, and look for the thin blue lines – some of these streams will be unnamed, but you’ll be able to see details like public land boundaries, access points, and more. 

TroutRoutes

Think of TroutRoutes like a state topo map on steroids. You get access to all of the details you would through the state’s map, in addition to features like real-time stream flow conditions and places to write your own notes. It’s a great resource, but it’s not free – the Pro version, which gives you access to all TroutRoutes features, will run you around $60 per year. 

onX

OnX is another great mapping resource, and you likely already have it downloaded if you’re a public land hunter. It has extensive land ownership information and clearly delineates where you can and can’t legally be. It lets you track your movement and share it with others, which is essential for those of us who tend to get lost. Its only knock is that it’s not as fishing-focused as TroutRoutes. 

Gaia GPS

If TroutRoutes and OnX are geared towards anglers and hunters, respectively, think of Gaia GPS as more of a multi-purpose navigation tool. If you’re an angler that also likes to hike or mountain bike, it’s a great option. It doesn’t have the stream-specific info that TroutRoutes does or the land ownership details of OnX, but it’s got comprehensive trail maps that will get you where you need to go. 

Go Beyond the Maps

No matter the resource you use to locate your destination streams, seeking out local knowledge is always a good idea. If there’s a fly shop nearby, buy a few bugs and ask about the water nearby. You might not get their go-to small stream spots, but odds are you’ll get a good starting point. If you get the name of a river, trace it on your map and check out the tributaries. Now you’re not just clicking on random streams – you’re blue lining with a purpose.