Small locations = big rewards!
Recently I was fishing with a good friend of mine Jake Hood on the St. Joe River in Idaho. We were floating the river despite high water conditions and were having reasonably good success. During a quick break, Jake and I were talking about the type of water we were catching fish in when Jake mentioned the saying... "fish-the-margins". That phrase pretty much sums up spring fishing on our local waterways. If you follow our posts then some of this may already be redundant, but if not or you are new to fly fishing this will help you out when looking for the correct holding water in the spring.
So what did Jake mean by the phrase "fish-the-margins"? Well fish-the-margins means honing in on the small windows of holding water along the edges of the river banks. The holding water that is best is where trout can get relief from higher flows, while still accessing food. Water levels go up... margins get smaller. Water levels drop... margins get bigger. Get the idea?
Let's discuss a little further...
Jetties are rock points or fallen logs that extend into the river from the bank. This obstruction in the river will often create a pocket large enough for trout to hang in without working too hard. This window of holding water along the bank can be as narrow as a couple feet when the flows go up. Two feet of opportunity to catch fish on the lower St. Joe is certainly "fishing-the-margins"!
Indents in the river bank can be the same as a point of rocks extending out into the current. These subtle "dips" in the bank often provide relief from the main currents and a great resting place for trout, while having access to food. These indents in a river bank can be narrow, sometimes brushy, but super fishy.
Back Eddies are often created by these points or jetties and can be extremely good areas to find fish when flows go up. Sometimes the back eddies are big... sometimes they are very small... smaller than a raft or drift boat. Even though throwing your fly into pockets that are smaller than the drift boat may seem kinda pointless or tedious... well if the pocket has 1-10 fish in it that wanna eat your fly and you hit 10+ pockets like that in a day... you do the math on how many fish you can potentially hook!
Side Channels are where a section of the main river splits off and creates another smaller channel, like a braid. These side channels sometimes are fishable year round, but can often be only fishable during high flows. Think of these side channels as a small stream where fish can get out of the main river flow.
Back Channels are slack water areas where water backs into or diverts to when rivers go up. Same thing happens to fish... they move into these back water areas looking for relief from high flows. They typically do not have current so your approach to them would be the same as fishing a pond or small lake.
Remember... as water volume goes up... margins get smaller.