It's bold to make definitive statements about how fish act or where fish live at different times of the year. But with more than 40 years of smallmouth experience, I'm willing to be bold.
If we have what the business school professors call "perfect knowledge," that is, if we know all there is to know about this subject, then we would hold all information necessary to catch a fish on every cast. Perfect knowledge doesn't exist in the fishing world. Instead, what we have is general knowledge and from that general knowledge we make predictions.
Here's what we know. We know that water temperature is the primary predictor of smallmouth bass behavior. Water temperature drives smallmouth locations throughout the seasons. It drives the time of the spawn and whether the spawn will be successful.
Temperature dictates when fish start feeding after the winter doldrums, when they stop feeding after the fall binge and how much they feed to cope with their raging summer metabolism. Water temperature controls their diurnal movements as they shift between resting and feeding areas. Water temperature prescribes when and what forage becomes abundant and available.
Unlike reveille's bugle call in boot camp, which instantly transforms recruits from somnolence to hurried activity, spring comes to smallmouth waters in fits and starts. A few days of warm weather stir fish from their winter snooze only to have a cold rain drop them back into winter funk.
As the water gradually warms, smallmouth move from their winter haunts into spawning sites. It doesn't happen in a linear fashion on any body of water, nor does it happen in every river or lake at the same time.
In lakes, wind-protected shallow coves on the north shore warm first because they get the most sun. North shore smallmouth move into the shallows several days before their south shore brethren. Elevation of the lake plays a role as well. A lowland western lake never gets as cold as a high-altitude reservoir. Since their starting point is lower, it takes more radiant heat to wake up the smallies. Yet another factor is the lake's water source.
A river fed by snowmelt starts to warm and then is chilled by the flush of newly melted snow, even though it is a low-gradient river. A low-gradient stream typically warms faster than a high-gradient river.
What this demonstrates to the smallmouth angler is how important a thermometer, time on the water and careful note-taking are to angling success. The fish are hungry, but their bodies have yet to get revved up.
Spring is best broken into four periods. The distinctions, while somewhat arbitrary, are important because the fish will be at different levels, in both activity and the water column.
This is the first primal stirring from winter. When the water temperature tops the mid-40s, male and female fish begin to actively feed after going perhaps all winter without taking food. They rise from winter depths after a period of warm, pleasant weather, and a few head toward the shallows. If a cold front blows in, they retreat down in the water column.
Those anglers aching to get on the water during this phase need to pay attention to the water temperature. If it shows an upward trend, even a degree or two for a few days, then it's time to fish. When the mercury drops back down on a cold or windy day, spend the next few days checking your gear or getting the boat rigged, because the fish will have turned off.
When the water temperature rises, topping 50 degrees, smallies are on the move. The entire mature population points toward the shallows. Males and females energetically feed in preparation of the spawn. Some males will check out potential nesting sites between eating sessions.
In lakes, the fish will be spread across all available cover, such as rockpiles, weedlines, large woody debris, and man-made structure. In moving waters, focus on slack water, back eddies and cobble bottoms. Not all cobble bottoms are created equal.
Look for those with a mixture of rock sizes ranging from cobble to small car-sized boulders. These will hold amazing numbers of smallmouth bass of several sizes. Small fish will be pushed to the edges where habitat becomes marginal, while the biggest fish are stationed in front of and behind the best rock structure.
When the water temperature rises above 52 degrees, smallmouth bass waters transform yet again. Males that are going to spawn get busy picking out sites and building nests, activity that deflects their attention from feeding. The shallows are almost barren of females at this stage. The numbers of actively feeding males are reduced, but there are still plenty of feeding males in the shallows.
To find females, go deeper. They have moved, awaiting the courtship that will soon follow. Look for females in water 3 to 5 feet deeper than where the males are doing domestic chores. That means if the males are staging in water 3 feet deep, the females will be in 6-8 feet of water.
Biologists used to think smallmouth lived their entire lives within a single pool, never traveling more than a few hundred yards. Turns out some of these fish have signed up for frequent flyer miles. Some western rivers have huge resident populations of smallmouth. Each may also has a large migratory population which leaves its winter home to spawn in the warmer waters of smaller tributaries.
The numbers of fish and timing of the upstream migration into tributaries change from year to year, but savvy fishermen who understand the role of water temperature, reap huge rewards in the number and size of fish caught.
Water temperature also determines when smallies actually spawn; typically between 60 and 63 degrees. It's easy to catch nesting smallmouth. The nests, typically 2 to 10-feet deep, are visible to the wading and floating angler. The female moves any foreign object from the nest. The male aggressively defends his home against intruders, no matter their size.
After the spawn, fishing becomes gender-specific. Females drift from the shallows into deeper water to recover. Suspended in deeper water, they show little incentive to feed on a consistent basis, though once recovered from the rigors of spawning, they feed aggressively. Males stay in the shallows until they are free from nest-guarding and fry-protection duties. When parenting duties end, they resume feeding and can be taken in the shallows.
Summer sunshine and smallmouth bass go together even better than peanut butter and jelly. The warm water increases the smallmouth's metabolism, necessitating more feeding. As temperatures climb, so does activity.
Early summer is a period of transition. Spring runoff is over and river levels stabilize and slowly begin to drop. Of course, Mother Nature is unpredictable; there can be late spring or early spring and sometimes lingering cold in the mountains delays snowmelt making rivers run cooler than normal far into summer.
Once runoff occurs, irrigation rivers across the West fluctuate in volume depending on water use demands. A spate of hot weather increases agricultural demands, and water managers respond by increasing the discharge from upstream storage reservoirs. Water depth changes and changes in current velocity affect where bass live and feed. Those changes alter where the food lives, and the bass follow the food.
In this period of transition, river fish move from spawning grounds and disperse into areas that provide the best combination of food, security, and rest. Conventional thinking, supported by research, is that once summer smallmouth reach their summer habitat, they remain in that area until fall migration, unless forced out by environmental factors such as fire, flood, or drought.
CHECK THE TEMPERATURE
The two most important pieces of gear for a smallmouth bass fisherman are a thermometer and internet-connected computer. The latter allows the fisherman to check federal, state and local websites for current water conditions. A knowledgeable angler can predict what is happening with smallmouth by temperature. For example, if your home lake water was 52 degrees, then you would know the smallmouth were moving into the late prespawn stage, most feeding fish in the shallows would be males and you'd have to fish deeper to find the bigger females.
Real-time temperature information is not available for all waters. That's where your thermometer comes in handy. Before making that first cast, dunk the thermometer to get a clue as to where the fish are located.
The colder the water, the less smallmouth bass need to eat, and the reverse is true as well. If the smallmouth have not yet spawned, then their forage baitfish, crayfish and aquatic insects will not have spawned, either. That means all will be full-sized adults and your baits should match the naturals in size.
Crayfish are fall spawners, though the female carries the eggs until they hatch in the spring. The newly-hatched crayfish will not leave the female and become bass food until they've gone through several molts, each triggered by warmer water.
Temperature dictates when baitfish spawn. Threadfin shad need mid-60-degree water. Emerald shiners need even more heat before spawning. If you know the predominate forage in the water you intend to fish and its spawning temperature, then knowing the current water temperature tells you whether it has spawned, the size of bait to use and where to fish.
Damselfly and dragonfly nymphs are an important coldwater food for some smallmouth. Later, when the water warms, the adults become a primary food source.
Water temperature affects how the natural foods move as well. Since the natural foods and the smallmouth are cold-blooded, both move slowly in cold water. Adjust the rate of retrieve to match the water temperature so that your presentation matches that of the natural foods. The water temperature will not be uniform across the entire body of water.
Unless altered by another source like a tributary stream or underwater spring, shallow water will be warmer than deeper water. The presentation can be faster in the shallows where the water may only be 2 feet deep than it would be along the deep edge of a point.
PUTTING IT TOGETHER
As proof that the knee bone is connected to the thigh bone, smallmouth bass behavior is predicated on water temperature. The movement towards spawning sites, the spawn itself, the urge to feed and the food that is abundant and available all are controlled by the effects of changes in water temperature. The more you understand about your home water, the more and bigger fish will be on the end of your line.