The Key to Building Stronger Bass Populations

Ask a seasoned angler to define good bass habitat and you’re likely to hear about laydowns, weededges, creek channels, stumpfields, mats, red clay banks, chunk rock, shell bars—the list goes on. No doubt all are places frequented by adult bass, and all are good bass habitat. But good bass habitat means not only homes for adult bass, but also spawning sites and nursery areas where young fish find shelter from predators while transitioning rapidly from prey to predator.

Consistently strong bass populations have successful spawning, good survival, and moderate to fast growth for that region. These characteristics are all affected by habitat. Biologists have studied the habitat requirements of largemouth and smallmouth bass and have learned some management tricks to maintain or improve it.

Spawning Habitat

Bass spawn on firm substrate. Largemouth are fairly flexible—any hard substrate, generally in 2 to 6 feet of water, suffices. Largemouth bass are industrious, too, even ingenious. They may fan away silt or decayed plant material, uproot plants, or nest on logs, stumps, or roots, if the bottom has too much silt or detritus. Smallmouths are more finicky; for them, spawning is much more successful on gravel or cobble. Protection from wind and waves often is critical, as well.

In waters with fluctuating levels, elevation around spawning time can be important. Biologists often work with reservoir managers to avoid drawdowns or drastic fluctuations when the water is between 60°F and 75°F.

Cover is desirable but not essential. Nests are usually built next to stumps or rocks or under logs if this cover is available. Where spawning is sporadic due to limited cover, adding objects aids reproduction. Clearing silt off gravel banks can increase smallmouth spawning success. Half logs or spawning benches—planks raised about 8 inches off the bottom—have been found to benefit spawning by both species. Location of these structures is important: They need to be on firm substrate for largemouth, on gravel or cobble for smallmouth, and they should be deep enough so they won’t be left high and dry if the water level drops. Savvy managers place spawning structures at various depths to hedge their bets.

Nursery Areas

Young bass are the preferred forage of many predators including larger bass, so they naturally seek shelter like brush, dense vegetation, or rock. But their best defense against would-be predators is growth. The faster they grow, the fewer fish that can catch and consume them. And the bigger they are by late fall, the more energy they have to survive their first winter. The ideal nursery location offers cover and prey for small bass.

Bass up to 2 or 3 inches long often feed on aquatic invertebrates such as insect larvae. The abundance of invertebrates is related to the amount of surface area they can live on—a flat lake bottom provides substrate, but a brushpile offers considerably more living area. Beds of aquatic plants, even those with simple forms like eelgrass, provide even more substrate. It’s been estimated that a 5 percent area coverage of mixed aquatic plants in a 100-acre lake provides about the same amount of substrate habitat for invertebrates as do 11,000 Christmas trees.

Aquatic vegetation yields abundant cover and food, but it’s possible to have too much of a good thing. Expansive areas of dense vegetation are conducive to high survival of largemouth bass fry and fingerlings, but young bass grow slowly after reaching a couple of inches. They find a good supply of invertebrate food in the grass, but by the time they reach 2 to 3 inches, they need fish in their diet for rapid growth.

Richer supplies of small fish like shad fry are found scattered around, rather than inside dense vegetation, or are in open water. High survival of bass fingerlings in dense vegetation also can result in slow growth, since forage supplies may be insufficient to feed the abundant bass.

Vegetation typically boosts bass recruitment, but how much vegetation is enough? The number hasn’t been pinned down, but studies indicate that lakes with 25 to 40 percent coverage by aquatic macrophytes usually have good largemouth recruitment.