07/27/11
The other day, someone ask me a direct question that I don’t think anyone had ever asked me prior to that. The subject of the conversation was fishing dry flies versus fishing flies below the surface. He ask “what percentage of food trout ate from the surface versus that eaten beneath the surface”.
To further clarify the question, he continued by asking, for example, did I think it would be twenty or thirty percent on the surface versus seventy to eighty percent below the surface.
Although this was something that I had thought about many times, rather than respond with an immediate answer, I took a few seconds for me to gather my thoughts. During the ten or fifteen seconds I pondered the question, it flashed though my mind that trout food could be aquatic insects, terrestrial insects, crustaceans, minnows, baitfish and some other odds and ends. It also quickly hit me that the food varied depending on the type of water, species of trout and many other factors. As those thoughts were streaming through my mind, my mouth opened and I replied “no, not anything close to those percentages of food is taken from the surface of the water.”
I continued by saying “It’s probably more like one percent taken from the surface versus 99 percent from below the surface.” Before I finished the answer, I found myself correcting that to even a smaller percentage. I said something like “Actually, it’s probably even less than one percent that’s eaten from the surface”.
I’m sure by now, some of you are already questioning the answer I gave. Off hand, many anglers who don’t tend to think about the things trout eat quite as deeply as I do, (not as crazy as I am) it may seem more logical that something more like ten percent would be a better answer, especially since it had already been suggested that twenty or thirty percent may be a good answer. If I wasn’t thinking seriously about the question, I may tend to agree with the ten percent answer just because a ten percent estimate seems like a sensible, rounded-off quick response. Because I gave the question a little thought, I’m convinced the answer I gave was far more accurate than what I may have responded with otherwise.
I’m well aware that I’m still not giving you any reasons for my answer. I’m still trying to get your interest up about the subject, but now that I hopefully have accomplished that, here’s why I still think less than one percent is a good answer.
First of all, consider the types of food trout eat. All crustaceans are all eaten below the surface. In some streams, there are only a relatively few and in some streams, such as spring creeks, crustaceans represent a huge part of the trout’s diet.The amount of minnows and baitfish depends greatly on the type of stream as well as the species of trout but in all cases, minnows and baitfish are eaten below the surface.
Next, lets look at a food source many of you will probably disagree with me about. Terrestrial insects are eaten by trout and here again, the location and type of stream varies the amount for sure, but all things considered, terrestrials represent a minute amount of food eaten by trout. Yes, I’m aware stomach sample taken during the Summer and early Fall in many locations show terrestrials are eaten by trout. I’m also know that Angie and I have set surface skim nets for long periods during this time period (nights and days) only to discover almost nothing was captured. The results was far, far less than we anticipated. To get to the point another way, If you sit down and stare at the surface of a stream for hours (in the Smokies, for example), I would bet my last dollar you wouldn’t see the first terrestrial insect.
Also, consider that this food is only available for a part of the year and furthermore, when trout eat terrestrials such as ants, beetles, hoppers, inch worms, etc., they don’t acquire them all from the surface. Many are taken below the surface because most of these insects that only get into the water by accident, sink rather fast.
Now, let us consider what trout rely on mostly – aquatic insects. Starting with mayflies, consider that a mayfly typically lives 364 days of the year beneath the surface of the water. It lives for only a few seconds as a dun on the surface. Some live two and three years below the surface and only seconds on the surface as a dun. Some mayflies, such as the Slate Drakes that are plentiful in the Smokies, are never on the surface as a dun. They crawl out of the water to hatch. The female spinners of mayflies do mostly fall on the water when they deposit their eggs at the end of their life, but even they, sink rather fast. The males mostly end up dying on land but they can fall in the streams.
Caddisflies are on the surface even less than mayflies because many of them crawl out of the water to hatch. There are not that many species that hatch on the surface. They too, spend a few seconds as an adult on the surface versus a year beneath the surface. The egg layers do end up on the water, but only float for a few seconds and again, it’s mostly the females. The males usually end up dying on land. Also, many species of caddisflies crawl below the surface or dive to the bottom to deposit their eggs.
Stoneflies are a different story altogether. They all crawl out of the water to hatch. They are eaten up to that point only as an nymph. The female adults do come back to the water to deposit their eggs and most of them probably end up on the surface for a few seconds or minutes, but they too, end up sinking.
Midges, the last major category of aquatic insects trout feed on, are similar to the caddisflies. The adults are on the surface only for seconds compared to weeks and months below the surface. Most of them are eaten below the surface as a larva or pupa during the hatch.
When you really think about it, in most cases, one percent is probably a high figure for the food trout eat from the surface. By the way, just to add another curve to the answer, how often do you think a large brown trout in the Smokies acquires its food on the surface?
What does this have to do with your fishing? The answer is simple. The odds are far greater you will catch a trout below the surface as opposed to on the surface. Now what is James Marsh really driving at? I’ll get into that tomorrow, but the short answer is trout can see nymphs and larvae of aquatic insects, all of which are below the surface, far, far better than they can see insects on the surface of the water. Even so, anglers pay far, far more attention to their dry flies than they do their subsurface flies. In fact, in general, they tend to think all nymphs look alike (and they don’t) and they completely disregard larvae.
Oh, I almost forgot a thought passing through many minds right now. I too, enjoy catching trout on the surface more than I do below the surface.
Copyright 2011 James Marsh