There is something special about smallmouth bass. Maybe it’s their airborne acrobatics, often followed by a dive back to the bottom with line-breaking tenacity. Or maybe it’s their vicious, no-doubt-about-it strikes on crankbaits and jerkbaits.
Whatever it is, I go out of my way to fish for brown bass. My quest for bronze is shared by most bass anglers I know.
Mississippi has smallmouth bass — indeed, world-class smallmouth bass — in Pickwick Lake. A few are caught in Bay Springs Lake, but nowhere else in the Magnolia State. Given my magnetic attraction to brown bass, I have often wondered what limits their occurrence.
Limiting factors
Water temperature restricts the distribution of many fish. Based on measurements for wild fish, smallmouth prefer water temperatures in the low 70s, while largemouth prefer about 80-82 degrees. Therefore, high summer temperature is a logical limiting factor for smallmouth bass, especially in the Southland.
However, summer water temperatures in Pickwick commonly reach the high 80s. Water temperature isn’t any cooler in Pickwick than in other reservoirs or streams in Mississippi. Furthermore, there are many lakes north of Mississippi that lack smallmouth even though summer water temperatures are far cooler than Pickwick.
Water clarity is another limiting factor. No doubt about it — clear lakes, like the Great Lakes in the North and Dale Hollow in Tennessee, support robust smallmouth populations. But some moderately turbid lakes in Oklahoma and some very darkly stained lakes in southern Canada also provide notable smallmouth fishing.
Rivals or relatives
A lot of anglers think largemouth eat shad and sunfish, whereas smallmouth eat crayfish. True, but largemouth eat crayfish when they can get them, and smallies eat fish — gobies in Lake Erie, shad in Pickwick and yellow perch in northern lakes. Largemouth and smallmouth are both opportunistic feeders, and eat the same foods. Could food competition with largemouths limit smallmouths?
Pickwick Lake is a good example that suggests competition does not exclude one species — largemouth and smallmouth have both persisted in Pickwick since the lake was built. Throughout their overlapping ranges are many lakes and reservoirs cohabited by both largemouth and smallmouth bass. Food competition doesn’t hold up.
More telling are growth-rate assessments conducted in New York lakes that have both largemouth and smallmouth. Cornell University fishery researchers found that when one species had good growth, both species had good growth. And when growth slowed for one species, it slowed for the other, too. If competition were occurring, one species would be expected to be suppressed more than the other when forage is scarce.
Youth are the future
In an effort to understand why smallmouth occur where they do, the Cornell researchers turned their attention to young bass. Lake samples revealed young largemouth were collected almost exclusively in areas with aquatic vegetation, while young smallmouth were abundant in rock and gravel habitat. Still lacking a clear explanation, the Cornell researchers designed a pair of experiments.
In the first experiment, both bass were provided with the same forage in cobble and aquatic-vegetation habitats. Largemouth consumed similar numbers of forage in both habitats. Smallmouth, on the other hand, ate more in the cobble habitat.
In the second experiment, juvenile bass were exposed to predation by adult largemouth bass. Survival of young largemouth was higher in the vegetated habitat, lower on the cobble substrate. Smallmouth had low survival in vegetation but higher survival on cobble substrate.
Cobble substrate is the preferred habitat of young smallmouth. In their preferred habitat, they eat more, grow faster and are better able to avoid predation. Young largemouth prefer vegetation and have better survival there but can forage effectively in other habitats.
What limits smallmouth?
Survival of young bass is essential to produce adult bass. While much remains to be learned about where smallmouth live, it appears that rocky habitat is one of the keys to successful populations. Certainly, any efforts to establish smallmouth within their native range need to consider the availability of rock and cobble habitat.
Kentucky Lake, Pickwick’s downstream and younger sister reservoir, has supported a strong largemouth bass population since the late 1940s. The smallmouth population began expanding about 20-25 years ago. As the reservoir aged, shoreline erosion exposed more rock and gravel, which might have created conditions favoring survival of young smallmouth.
Might similar changes occur in Bay Springs as the shorelines steadily erode? I’m starting to see a little bit of chunk rock up there.
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