Bass Week: Factors for Big Bass

Powered by Strike King and Lew’s

Editor Note: From the pages of the May 2024 edition of In-Fisherman Magazine

For the last 100 years, unusually large largemouth bass have inspired a remarkable level of interest among anglers worldwide. Once railroad lines extended to Florida from big northern cities, affluent anglers traveled to the original big-bass mecca of the Sunshine State in their quest for wall-hangers. While big fish are always a draw, specialist anglers who favor walleyes, trout, panfish, marine species, or even muskies seem less focused on catching unusually large ones.

Genetics

As our knowledge of fish genetics has grown over the last four decades, we’ve seen how important these microscopic molecules are in determining fish behavior, growth, and many other characteristics. Now that the foremost fish genetics experts have determined that what we once considered two subspecies of largemouth bass are indeed two species—northern largemouth bass and Florida bass—genetics is even more central to this discussion. Since Dr. Carl Hubbs’ designation of the subspecies, Micropterus salmoides salmoides and Micropterus salmoides floridanus in the 1930s, we’ve focused on these two types that readily interbreed when brought together in suitable habitat.

In the early 1980s, Dr. David Philipp and his team from the Illinois Natural History Survey used electrophoresis to genetically define the natural habitat of Florida largemouths and an intergrade zone where largemouths seemed to have characteristics intermediate between the northern largemouth bass subspecies and the Florida subspecies. It extended from northern Florida north into Maryland and west through Mississippi. Genetic analysis showed Florida bass subspecies only in peninsular Florida, and northern bass in the rest of the U.S., except Texas, California, and a few other states where Florida bass had been introduced.

In 2002, a team of biologists used more advanced techniques including mitochondrial DNA to define Florida and northern bass as separate species. The transition to this concept is still ongoing among anglers and management agencies. Since then, further species differentiation among other black bass species have been documented by genetics experts.

The large size of bass from these areas encouraged some state agencies to stock Florida bass to increase bass size in their waters, though many introduced fish were from the intergrade zone. Recent genetic work, combined with field studies, has shown that largemouth populations are locally adapted to their typical ambient temperatures throughout the year. For example, bass brought to Minnesota from Tennessee or even southern Illinois to can’t survive their first winter. So the species as a whole is highly temperature-tolerant, individual populations are far less so.

Northern and Florida largemouths readily interbreed, so a great deal of mixing has occurred. Where habitat wasn’t suitable for Florida bass genes, their representation in the population dwindled and little increase in bass size was seen. In other, general milder areas, introductions boosted maximum size dramatically. The interaction of environment and genetics is a very complex one, given the dictates of natural selection and evolution.

Habitat Factors

Like all other fish species, largemouths have a particular suite of habitat characteristics that are conducive to good reproduction and growth. This highly adaptable predator was endowed with an unusually broad range of conditions where it can thrive. I’ve caught largemouth bass in natural waters where the water temperature ranged from 38°F to 93°F, in waters from northern Minnesota to Florida, in canals, tiny farm ponds, and million-acre lakes.

After the last Ice Age receded about 25,000 years ago, bass found increasingly acceptable conditions in recently flooded (in geologic terms) areas that had been under hundreds of feet of ice. In the vast melt, lakes and rivers formed and gradually warmed over thousands of years. The range of largemouth bass expanded from the Southeast to the west and north through connected waters as temperatures gradients allowed.

When European scientists first visited the continent in the 16th century, the largemouth range covered much of the eastern U.S., south of the Great Lakes. Commonly found in creeks and small rivers, largemouths favored quiet backwaters as well as natural lakes where their greenish color, big mouth, and measured swimming speed made them a top predator among fishes, though vulnerable to various reptiles as well as humans.

We now find great bass fisheries in expansive reservoirs built by damming major rivers. Some of them offer abundant submergent vegetation, often of non-native origin, as the novel environments provided suitable conditions. In other reservoirs, particularly ones with hard substrate or murky water, bass live near brush, among standing timber, or along rock structure. In general, however, the species seems to find peak survival, abundance, and growth where vegetation is available.

Several lab studies have tested the effects of water temperature regimes on the food consumption, growth, and mortality of largemouth bass. Early studies suggested that little feeding occurred below 50°F and digestion was very slow below that mark. Feeding rates of adult fish increased with rising temperature up to about 80°F, while young bass grew considerably faster at higher temperatures. Bass metabolism increases with temperature until it approaches lethal levels (around 98°F for fish in southern waters, considerably less for northern populations). Growth studies have noted faster growth in populations living at lower latitudes, generally exhibiting a south-to-north gradient. State records generally demonstrate this trend.

Consistently warmer water tends to boost production of lunker-size bass; say 10 pounds. As a result, Florida, Texas, and Southern California have produced the vast majority of huge bass in the U.S. While impoundments in Japan have produced giants, including the all-tackle record-tying fish from Lake Biwa, lunker catches from sub-Saharan Africa are far more common. Milder coastal areas also tend to produce larger bass, such as Massachusetts and its amazing state record of 15.5 pounds, caught ice-fishing in a coastal pond.

The Need to Feed

Largemouths don’t have their huge maws and large bellies to improve their appearance, as their human fans overlook aesthetics in making them the most popular species. Prey availability is certainly a key factor in bass growth. In addition to the cooler waters in northern states, prey selection is generally not as nutritious as in more southerly regions where shad, blueback herring, and large wild shiners are available, or where trout and kokanee are stocked in western waters. Crayfish are a dominant prey in northern lakes. Bass are drawn to them and their peekaboo behavior that we try to imitate with our jigs. Bass can easily catch them despite their formidable defenses.

Studies of bass diets in Wisconsin and Minnesota have found that crayfish make up as much as 60 percent of stomach contents by weight in some waters. Ecologists have wondered about this food choice since about 50 percent of the dry weight of a crayfish is composed of organic salts and chitin, substances not digestible by fish. So they’re not energetically favorable, compared to many preyfish species. Their benefit may be sheer abundance and their relative ease of capture.

In many lakes, sunfish and perch also are common prey, but their spiny defenses make them more challenging to catch and they require more handling time to eat than fish without spines. Bass can grow large on such a diet if conditions are otherwise favorable, as evidenced by the many giants caught from farm ponds across the Midwest and Southeast.

Gizzard and threadfin shad form large schools that bass can more easily focus on, and they can be quickly gulped down and digested. Behavior of these baitfish encourages bass to engage in schooling behavior, providing feeding advantages when several predators attack from different directions, devouring shad over deep water.

The famous boom in giant bass that took place in California from 1973 to 2006 produced all the largest bass caught since George Perry’s 1932 world record. It resulted from the introduction of Florida bass on top of native northern largemouths, as well as widespread stocking of 10- to 14-inch rainbow trout. When bass were brought to California in the late 1800s, they came from northern states, where maximum size was less than double digits. Indeed, the California’s record hovered in that range until the newcomers grew up and began spawning.

After Florida bass introduction in 1959, the incredible flurry took off with Dave Zimmerlee’s 20-pound 15-ounce giant and exploded with catches of huge fish, including several others over 20 pounds across Southern California. Some of them were caught on trout-imitating lures that matched the size and color of stocked rainbows. Moreover, successful anglers fished the lures to imitate the erratic behavior of raceway trout released in deep clear lakes. About 15 years ago, state budget crunches led to reduced trout stocking and California bass fisheries changed. These reservoirs don’t contain shad, so bass transitioned to a more diverse diet and the number of giants dropped dramatically and remains far lower today.

Let ‘em Go to Grow

Most of the earliest lunker hunters kept whatever they caught. In historical archives, we see photos of gents in top hats and ties hoisting stringers of huge Florida bass. The naive fish were easily fooled with big live shiners or jiggerpoles rigged with wooden plugs or flies. Newly discovered bass lakes contained fish with maximum age structure—dominated by old giants. George Perry’s record catch in 1932 from South Georgia represents this situation, the maximum size largemouths reached in remote and productive waters in semi-tropical regions.

During the 1960s and ’70s, anglers witnessed declines in bass fishing, particularly in impoundments, while fisheries sampling indicated reduced abundance, particularly of larger bass. Generous bag limits and increasing angler sophistication, mixed with a traditional harvest orientation combined to bring about poor fishing in many waters. In the 1980s, novel length limits were enacted and tournament policies for catch-and-release quickly reduced harvest rates of bass in most areas. Populations gradually responded to the new regulations while catch rates and percentage of larger bass in the catch increased in many waters.

Biologists in Florida and Texas calculated that fishing mortality of bass declined almost 50 percent from the period from 1976-1989, compared to 1990-2003. Since then, it’s undoubtedly dropped more. Results of Texas’ ShareLunker program, begun in 1986, demonstrate that releasing giant bass allows them to be caught again and again. After being caught and used in hatchery propagation, they’re returned to their home lake, and several have been recaptured. Moreover, the number of first- and second-generation offspring of ShareLunkers that grow over 13 pounds and in turn become part of this propagation project, is remarkable, a testament to the benefits of catch-and-release, as well as the genetic heritability of extra-large size.

On the other hand, moderate harvest of young bass from about 11 to 14 inches can boost growth rates of productive fisheries and enable more fish to grow large, given an initial opportunity for faster growth at a young age. Biologists have found that growth rates of bass, as well as other species, is density-dependent. Larger size helps young fish avoid predation, consume larger prey, and grow faster. Today, voluntary release of bass is so prevalent that growth rates often are reduced due to intraspecific competition for food and habitat. It can be a hard sell for fishery managers faced with such a strong catch-and-release ethic, but bass anglers should feel free to enjoy fish meals. Bass of this size are the tastiest, and also the safest to eat from a contaminants perspective.

Special Situations

Warm-Water Discharges: Given the boost to growth that warm waters bring, it’s not surprising that artificially warmed impoundments, typically receiving heated water from power plants, are capable of growing unusually large bass for their region of the country. The effects of warmwater discharges on growth potential are strongest in waters where normal temperatures fall below 40°F in winter. During generation, warmed water is released from an outflow canal, gradually mixing with the ambient water, creating a temperature gradient. This offers bass a choice of temperature regimes.

Their general preference for warmer conditions is demonstrated by the number of “hot water” lakes that produce unusually large bass, many caught in the effluent during winter. Minnesota offers a few options while Nelson Lake in North Dakota is arguably the best open-water option in the northern fringe of the largemouth range. It produced the state record of 8 pounds 7 ounces. In northeast Kansas, LaCyne Lake, a 2,800-acre impoundment, provides cooling water for a coal-fired power plant. Electrofishing by biologists with the Kansas Department of Wildlife, Parks, and Tourism has revealed an unusually large proportion of big bass. And anglers have caught 10-pounders there. Similar examples exist across the country.

Newly Flooded Waters: Bass are known to achieve fastest growth in newly flooded waters, whether in a new reservoir such as Lake Fork when it was impounded in 1980, or a farm pond. Fish often surpass 12 inches at age-1, three to five times faster than in established fisheries. Some waters, such as Fork, may sustain this growth boost for many years, though it declines even in the most productive waters. In other cases, habitat loss and water level fluctuations reduce catch rates and lunker potential dramatically over the decades.

Reflooding can, however, stimulate a “new lake” effect, whether done by management action or the intercession of Mother Nature in the form of sustained rainfall. This is exactly what has provided two major bursts of lunker production at Lake O.H. Ivie in West Texas. The first one occurred around 2000, as anglers entered a flurry of ShareLunkers. Located in West Texas, O.H. Ivie is prone to periods of drought and flooding. Rising waters had boosted shad production and provided new habitat and cover for bass.

By 2017, Ivie’s volume had dropped to 14 percent capacity, and it shrunk to 4,000 acres. In preceding years, bass fishing had declined, and the lake was on no one’s lunker list. Heavy rains in the fall of 2018 raised the reservoir over 30 vertical feet, simulating a new lake effect that quickly rejuvenated the population. Within two years, production of big bass increased, and it’s produced the vast majority of ShareLunkers over 13 pounds in Texas ever since.

---