Smallmouth Bass Nest

Photo and information courtesy of Fishes of Wisconsin, John Lyons, Wisconsin Department of Natural Resources.

As a fly fisherman, it is important for you to learn everything you can about smallmouth bass behavior.  Your knowledge of the biology, environmental influences, spawning and feeding behavior are essential to success and the enjoyment of the sport.

On this page we will discuss reproduction and spawning behavior.

Water temperature is the most influential condition that triggers these fish to spawn.  Smallmouth bass spawn in the Spring.

Smallmouth bass move from their winter depths to shallower water when the water temperature reaches 50 degrees.   

Males build the nests on rock and gravel substrate when the water temperature reaches and sustains 55 to 60 degrees F.

Spawning continues until the water temperature reaches about 70 degrees and even higher.  After the spawn, it is widely known that the males and females spend time recuperating and feeding very little.  After the “rest period”, and if the water temperature rises to the smallmouth bass’s preferred temperature range of 68 to 80 degrees, the fish begin eating everything they can find.  That is when we should all be fishing for smallmouth bass. There is a perfect time to fish for smallmouth bass and on those special days, lifetime memories are made.  I have fished on those perfect days only a few times in my life.  

Water temperatures and the effects on spawning behavior vary but the numbers mentioned above are close.  So remember, smallies move into shallower water when the water temperature reaches 50 degrees.  They spawn when the temperature averages between 55 to 70 degrees.  The feeding frenzy follows when the water temperature is between 68 and 80 degrees.  These facts should be etched in your brain if you fly fish for smallmouth bass. 

Nest building often occurs at the same location where a particular fish has built a nest before.  The male smallmouth bass fans the area with his tail, removing silt and fine particulates.  Sometimes this may just take a few hours.  The nest may take up to two days to prepare. 

Once complete, it is hopeful to the species that a female will lay her eggs in the nest to be fertilized by the male.  After that takes place, the male guards the nest until the fry hatch.  The larva drop into the gravel in the nest then emerge a few days later and disperse.  Following the scattering of the young, the male is free to leave.

This process takes a few days.  It sounds simple and productive doesn’t it?  Not quite.

As we all know, water temperature varies widely in the Spring.  Water levels vary as well.  Everything may be going just fine, the male is building his nest, then a cold front moves in and drops the water temperature.  The male may abandon his new nest.  Water flows in rivers or depths in lakes may cause the same result.  When the water level recedes and the water temperature gets back to around 55 or 60 degrees, the male may build a new nest or go back to his former nest.  This may happen several times during the Spring.  The male smallmouth bass may give up and call it a year without any offspring.  Actually, a very small percentage of adult smallmouth bass actually have a successful spawn in a given year.

Spawning may occur at different times within a reservoir or river. You may see nest building in one location and abandoned nests in others due to the water conditions.  Females are typically larger than males.  If you catch a thin looking 20 inch smallmouth bass, you can be fairly sure that she is a she, and she has spawned. If you catch a large, overweight fish when the water is cold, return her quickly to the water.  That fish is most likely a pre-spawn female, full of eggs.

Knowing when all of this activity is happening in the waters where you fish is essential to fly fishing success.  And, unless you fish several days a week during the Spring, it is hard to predict the stage your stream, river or lake is in unless you are there to take the water temperature.  For that reason, those smallmouth fly fishing days of a lifetime are often the result of good luck.  If you catch 40 or 50 smallmouth bass during a day of fishing, you have found the perfect time.  Maybe you were lucky.  Maybe that won’t happen again next week or the week after.  It may not happen for years. 

The more often you fish during the Spring increases your success chances substantially.  One of those days will be that perfect day.  When it happens, you will know it.

Byron Begley