Smallmouth are different from trout in many ways. One of these differences that really trip up trout oriented fly rodders is the food issue. In recent years, most fly fishers have finally figured out that smallies don't eat many insects, but mostly large forage, such as crayfish and minnows. So most fly guys now realize they'll need to use something larger than a #12 nymph.

    However, a lot of fly fishers still don't understand is that the forage differences between the species also affects many life cycle and behavior aspects of smallmouth.

    One forage determined difference is the density between the species. Because smallmouth eat higher on the food chain, their densities are often 3 times lower per acre than the densities of the insect eating trout. And if a person fully comprehends this, it's obvious angling tactics should be adjusted to match these lower fish densities. Instead of expecting to catch a dozen fish from a small pool like you might with trout, it's more likely that there are just 4 or 5 willing-to-bite smallies in that spot. And these lower densities should also influence how much water you cover in a day. Instead of a fishing just a quarter mile of stream like you may for trout, 3/4th of a mile of stream is more realistic, if you want to catch the same numbers of fish.

Feeding Less
    Here's another food related difference between the species that still seems poorly understood by lots of folks. Smallmouth feed less often than trout do! I don't think there have been many studies where smallies have been observed for long periods to see how often they eat. But angling results certainly bear out the assertion that smallmouth often quit feeding, and in fact can go for prolonged periods without eating.

    While trout must continuously sip tiny drifting insects to keep its stomach full, because smallmouth consume such large forage (and they have to burn a lot of calories to capture this highly mobile prey) it makes biological sense for them to "rest" (quit actively feeding) when conditions aren't favorable. For example, in extra clear waters with a great abundance of crayfish, it might not make sense to burn lots of calories actively hunting for crayfish while most of them are hiding under rocks. Conversely, aggressively feeding during the evening (when the crawdads are out and about) would mean the smallmouth can score the most amount of calories, while expending the least energy. And on a lower visibility river, with less forage available, it might make the most sense for the smallies to feed aggressively during midday when visibility was best for spotting prey.

    These forage determined differences also influence how quick trout and smallies turn "on" and "off." Many trout fans assume if stream conditions turn bad and cause a big decline in fish activity, once conditions improve a little, the trout will be hungry and raring to feed-- often within a day or two. But this quick change in feeding activity generally isn't true for smallies. Smallmouth in a stream that muddies up after a rain or experiences a big temperature drop often stay inactive for days, sometimes a week.

    Again, I believe this difference in behavior is mostly forage determined. Before the poor conditions set in, the smallmouth likely filled its belly with large (and slow to digest) prey, so it can afford to sit out the muddy, high or cold conditions. And even if it does a little feeding during the bad times, one gulp of a 4 inch shiner may tide it over until conditions improve.

    Of course, savvy anglers know smallmouth can still be caught during these "off times." But fishing techniques and tactics need to be significantly adjusted. Instead of quickly working a topwater or shallow running subsurface fly, to be successful you'll likely need to fish much slower or deeper or cast to the same spot more times. But if a troutcentric person don't realize there are plenty of the times when the smallies are neutral or inactive, they aren't likely to quickly adjust their tactics.