Dan Munger holding a nice fly caught smallmouth bass.

A smallmouth bass fly fisherman, needs to understand to some extent, what these fish eat, in the waters being fished.  Smallmouth bass are top carnivores and predators. They eat just about any living creature found in their ecosystem, if the creature is small enough to swallow.
 
Smallmouth bass feed mostly during the daytime hours, with the highest actively at dawn and dusk.  They do feed at night, during the warm months.  I know that for a fact.

What a smallmouth bass eats depends on many factors, some of which include:

Availability of food
Age or size of the bass
Size of the available food
Season
Water temperature
Air temperature

Availability of food varies from lake to lake, river to river or from one geographical area to another. Your favorite river or lake in Tennessee may have a totally different food base than a river or lake in Michigan.

Juveniles eat crustaceans, zooplankton, aquatic insects and other small aquatic organisms.  When they grow larger, they become predators.   

If your favorite river has a large population of sculpins, you can be assured, smallmouth bass are eating them.  Crayfish make up a large percentage of forage for smallmouth bass, when available, especially older and larger fish.

Fish and minnows are likely prey for smallmouth bass. 

Threadfin shad may be a significant source of food, in the warmer climates, during the summer when they are abundant, or during the winter, if they are dying due to cold water.  Smallmouth Bass do not eat much during the Winter months, but a dying threadfin shad drifting by is tempting.  We know amphibians, are eaten by smallmouth bass, including lizards and frogs.

During the warm months, when terrestrial insects are active, smallmouth bass will feed on those unfortunate enough to fall in the water.  My favorite smallmouth fly looks like a huge beetle. If you a lucky enough to be on the water, when cicadas are abundant, you can have the time of your life. 

Streams with good water quality, and the proper substrate, in North America, contain thriving populations of hellgrammites, the larva of the dobsonfly.  Any fly fisherman targeting smallmouth bass should have a good hellgrammite pattern in his or her fly box, when fishing these streams.

You don’t need to be an aquatic entomologist or fisheries biologist to determine what the bass in your favorite stream or lake are feeding on.  Over time, you will learn.  Try fishing with different flies, representing known creatures living in your waters.  Smallmouth bass are opportunistic feeders.  Watch their behavior. I’m not a big fan of pumping stomachs of fish I’ve caught.  I release all my smallmouth bass immediately.  

I don’t know how many times I’ve seen crayfish claws sticking out of the throat of bass I have caught.  I have witnessed hooked smallmouth bass regurgitating minnows during the fight many times.  Spend time on the water and you will learn.

Byron Begley