Why Largemouth Bass Grow Bigger in The South

Fish Facts
Another prime example of a true trophy Largemouth bass.
Another prime example of a true trophy Largemouth bass.

People in the great state of Texas have been managing private waters to produce double-digit Largemouth bass for decades. Over the past 30 years, this trend has spread nationwide and has become somewhat mainstream among affluent landowners and outdoorsmen. As the industry continues to mature, trends continue to emerge. This has helped biologists better understand why bass grow larger in some areas and not others.

Largemouth bass grow bigger in the South. This makes sense since Florida strain Largemouth bass have the genetic propensity to reach larger sizes. They thrive in southern regions since cold water is lethal to them. As biologists work to push bass growth, they ask the question: Is the most significant advantage due to genetics, or are other variables fueling this advantage?

To answer this question, it is essential to understand that many of the most successful trophy Largemouth bass fisheries within each state have some essential characteristics in common. Beginning with good water quality, they can produce a great deal of phytoplankton, which is continually grazed upon by a robust zooplankton population. This fuels both a thriving invertebrate and forage fish population, which is continually being consumed, suppressed, and renewed by a dynamic population of carnivorous bass.

Sounds relatively simple, right?

Veteran fisheries biologist Paul Dorsett shows off a massive Florida strain largemouth bass in a lake he helps manage
Veteran fisheries biologist Paul Dorsett shows off a massive Florida strain largemouth bass in a lake he helps manage

So, what advantage does the South have? The answer is simple - warmer water temperature. Water temperature is the most critical variable impacting trophy Largemouth bass fisheries. Temperature is the primary driver that influences the home range of the superior Florida Largemouth bass strain. Equally important, water temperature influences the production of phytoplankton, which leads to the production of forage fish. Simply put, phytoplankton, zooplankton, invertebrates, forage fish, and Largemouth bass rely on optimal temperatures to thrive.

For this article, the area of the United States where Florida strain Largemouth Bass can survive year-round will be referred to as the "Southern Region."

As indicated above, this southern region has far more plankton growing days, which is the rocket fuel that propels forage fish populations further than waterbodies north of them. This extended growing season means more opportunities for forage fish to reproduce and reach larger sizes within a growing season. This all leads to growing more pounds of forage fish using plankton compared to water in the northern states.

Forage fish are not always thought of in terms of genetics, but that is also a key component. Each forage species has a desired temperature range and lower and upper lethal limits. It just so happens that these southern waters have a genetic advantage with forage species. For example, Threadfin shad can survive winter in some southern climates. This results in bigger bait the following year for bass to consume. Bigger bait helps grow bigger bass. Likewise, the overwintering of shad allows for more robust recruitment the following spring. Tilapia are another excellent example. Although they do not overwinter throughout most of this Southern Region, they can be stocked earlier in the year and die off later compared to cooler climates. This results in a greater biomass of forage produced within a calendar year. With the diversity of forage fish, pressure can be relieved from the primary forage fish, the backbone of the food chain for largemouth bass and bluegill sunfish. The improved performance of forage species provides a significant advantage year over year.

On the other hand, maintaining proper-sized forage can be a big challenge for areas to the north. Some of these cooler climates can stock Threadfin shad; these shad start later, resulting in fewer generations of young of the year present in a growing season. Rather than reaching large sizes, Threadfin shad typically die off due to water temperatures dropping to lethal levels. As a result, these waterbodies tend to struggle to maintain decent size forage fish. This puts more pressure on other forage species, such as bluegill, which struggle to reach greater than 2.5-3 inches within their first growing season. This all leads to a higher probability of a smaller forage base than what is desired by the bass population.

As biologists continue to understand better why the Southern Region produces more trophy bass, they can better assemble strategies that will succeed elsewhere in the country. This has been going on for many years, but there is still much to be learned and applied.

Don't discount the value of appropriate genetics for your forage fish, either. Use local genetics, especially for bluegills. These sunfish are fast-growing youngsters, on their way to becoming hearty meals and continually adding young of the year to the food chain.
Don't discount the value of appropriate genetics for your forage fish, either. Use local genetics, especially for bluegills. These sunfish are fast-growing youngsters, on their way to becoming hearty meals and continually adding young of the year to the food chain.

Stocking F1 Largemouth bass is one solution introduced many years ago to address the genetic issue of inferior bass. These F1 bass are created by breeding Florida and Northern strain Largemouth Bass with each other, resulting in offspring that can tolerate colder water temperatures than their Florida strain parent while reaching larger top-end sizes than their northern strain parent. As with the Florida strain, these Fl's have a lethal cold temperature limit, restricting how far north they can survive in the winter. Although somewhat subjective, Fls typically do not survive in areas of the country where lakes and ponds ice over regularly each winter. There are some exceptions.

One downside to the improved genetics happens when Fls spawn with each other. Offspring produced are genetically inferior to their F1 parents, especially regarding top-end growth expectations. As a result, trophy fisheries that have Fls present should take additional management steps to offset this challenge by stocking more Fls from time to time. If you live up north where Fls cannot predictably survive (some states outlaw them), remember that northern strain bass will often top out 30-50 percent smaller than the Florida strain bass if appropriately managed. Fls, on the other hand, can get much closer to the size of Florida strain bass, although they won't typically grow as big as their southern cousins.

The biggest challenge faced by areas north of this Southern Region is overcoming the headwinds related to productivity. Northern climates warm up slower than southern climates. This means southern waters are producing a dense plankton population while water to the north is still too cold.

Overcoming this challenge sounds daunting, but it is not impossible. To close the gap on the reduced number of phytoplankton growing days, managers must make the most out of each warm growing day they are provided. Getting the bloom off to a slow start in the spring or letting it fade away too early in the fall are significant oversights. During the growing season, plankton species should contribute to the food chain and have an 18-24-inch visibility. Pushing waterbodies with this plankton density will strain water quality, so proper measures must be taken. Think aeration.

If northern waters hope to grow close to the same biomass of forage fish within a calendar year, they need to produce this biomass within a shorter period because of the shorter growing season. The only realistic method available to grow forage faster than with plankton is to supplement with high-quality fish food. These waterbodies must feed their forage fish aggressively throughout the entire growing season. When executed correctly, this helps overcome productivity headwinds.

As productivity increases, it is essential to understand that proactive water quality management is needed to prevent fish stress and winter fish kill. Some key parameters to pay attention to are dissolved oxygen, pH, alkalinity, total phosphorus, and total nitrogen. In many cases, monitoring and keeping these parameters within their desired ranges can be expensive. Still, if done successfully, the food chain will have a significantly better chance of thriving.

When looking at water quality by region throughout the country, the Southern Region also has a challenge. Surface water temperatures become hot in summer. Hot water may be suitable for forage production but not so good for largemouth bass. Unfortunately, this issue is not easily resolved. The best solution to this temperature challenge is to have a decent volume of water between 12 and 20 feet deep, as this deep water provides cooler water temperatures for bass. Maintaining sufficient dissolved oxygen towards the surface and in this deeper, cooler water is challenging.

As a generalization, Southern Region waters struggle to maintain consistently sufficient oxygen levels due to the hot summertime water temperatures.

It is essential to understand that trophy Largemouth bass are a byproduct of many things going exactly right for many years in a row. Just because you live in the South does not mean you will succeed in growing double-digit bass or that your fishery will be better than someone who lives further north. But yes, the southern tier of states indeed has a sizable Largemouth bass genetic advantage, coupled with climate advantage for forage fish, resulting in their fisheries being superior to those further north. And yes, they naturally have more growing days, produce more plankton, and produce a larger biomass of larger forage fish.

David Beasley is a Fisheries Biologist and the Director of Fisheries at SOLitude Lake Management, an environmental firm providing sustainable lake, pond, wetland, and fisheries management services. Learn more about this topic at www.solitudelakemanagement.com/ knowledge.

Reprinted with permission from Pond Boss Magazine