Largemouth Bass Biology

North American Fisherman Magazine

largemouth bass

The largemouth bass has an interesting scientific name, Micropterus salmoides. This classification actually makes it a member of the sunfish family. Yeah, a sunfish.


Largemouth bass can be found from southern Canada to Mexico. These are native to North America, but have been introduced all over the world. It is widely believed that largemouth only inhabit shallow, weed covered water. Nothing could be further from the truth. Most of the biological information comes from scientists, not fisherman. As with their close relatives, smallmouth bass, you will find them relating to the deepest water in their area. A point to remember that will be covered in more detail later.

Water temperature and oxygen content affect where you will find largemouth as well. They tend to like warmer water and can tolerate lower oxygen levels than smallmouth. Typically 75-85 degrees is their “perfect” temperature. When the shallows get too warm, during the dog days of summer, largemouth will tend to head to slightly deeper water to stay in their comfort zone. This is especially true of the biggest fish. This establishes the stopping point of their migrations to the shallows.


Largemouth bass get their name because their jaw extends past the rear of the eye. They have a horizontal black stripe that kind of looks like a heart monitor. Maybe that's why they get ours hearts racing?

They are basically dark green on the back that fades to white on the belly. They can vary in color due to their environment and spawning activity. It is not unlike land animals, that vary in shade and color. Like most predators, their camouflage is extremely effective.

The females are the larger sex. That being said it is nearly impossible to tell the difference between male and female. During the spawn if the fish is gently "milked" toward the anal opening, either sperm or eggs may be visible. That is about the most reliable way. Generally if the bass is greater than 8 or 9 pounds, it is a female.

largemouth bass


Largemouth bass spawn in the spring. When exactly they spawn is determined by water temperature. This tends to be 55-60 degrees. As with all animals, some react sooner than others. There has been debate on fishing during the spawn. Most studies show no adverse affect on bass survival as long as they are released immediately and handled with care. Sight fishing bass during the spawn will teach you a lot about bass behavior.

The males make the nest in the sand with their tails. The also will protect the nest and the hatch. Obviously the females lay the eggs, but that's about all they contribute. Early in the season is when fishermen tend to have better catches, as a lot of the big fish are shallow. Knowing where fish spawn in a certain area is key information to locating them later on.

You will notice that after the spawn, sunfish will occupy the old bass beds. This also shows the true family of the “bass”.

The young bass will stay close to PAPA for about 1 month. The young males also reach maturity before the females. Boy, all of this could start an argument with the wife!

largemouth bass


Largemouth bass, like a lot of predator fish, tend to be more active early and late in the day. This is not because they can tell time. Light intensity is the key. You will see this information again! Most of the time, most of the fish will not be shallow. You will definitely see this information again. Understanding this,and accepting it, will make the difference in your fishing success.

Food is taken when the opportunity arises. Largemouth bass will eat quite a few different prey. Like people, they do have their favorite dishes.

Some of there favorites are crayfish, bugs of all types, small land critters, frogs and just about anything slightly smaller than themselves. This presents a lot of opportunity for fishermen.

Largemouth are not the by nature a solitary animal. They actually key off each other to locate feeding opportunities and warn of danger. Catching a bass, if it is landed quickly, can set off a mini feeding frenzy. Likewise if you fool around with a hooked fish too long, you can easily spook the rest in the area. The same holds true if the largest fish is caught. It sends the school into a panic that will kill the fishing for a while. If the bite does drop off, it is best to leave that area and come back later. This gives the fish an opportunity to settle down. Good thing fish have a short memory!

Largemouth have a highly tuned sense of smell. The slightest sent trail can be zeroed in on by it's nostrils, called nares. It is not different from the way a dog or bear can be seen testing the air. Lure manufacturers have keyed in on this with a variety of scented baits and sent additives. These can be very effective it triggering the bite instinct after the bass has found the source. Sent becomes even more important with slower moving baits such as Carolina or Texas rig soft plastics.

Largemouth bass also use their hearing to locate prey. They hear by picking up vibrations in the water using the lateral line. It is a grouping of nerves that run down each side of the fish underneath the skin. As an apex predator, like the Great White shark, this gives him a radar to find and eat struggling fish and even crawling bugs and crayfish. Noise making lures, such as bladed spinnerbaits or crankbaits with rattles, target this amazing hearing ability to trigger the bite.


A fact about largemouth bass is they do better in the wild than in captivity. This is not unlike all of natures other top predators. They can live as long as 20 years or slightly more in the wild. That would give them a lot of time to see goofy lures come and go. The average lifespan is around 15 years, but a lot can happen in 15 years.

Although there has been a lot of debate, the largest bass caught is 25 lbs. That is one big bucket mouth! A big fish in the northeast would be 6 lbs and up due to slowed metabolism caused by winter. In the south however, the average fish is much bigger because of the warmer climate. It is not that uncommon to catch a 6 pound fish in the south.

Largemouth Bass Biology from Bill Dance