Why Largemouth Bass Grow Bigger in The South

What it Takes for Northern Lakes to Compete

By Dave Beasley

 For decades, people in the great state of Texas have been managing private waters to produce double-digit Largemouth bass. Over the past 30 years, this trend has spread across the country 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. And, they thrive in southern regions since cold water is lethal to them. As biologists work to push bass growth, they find themselves asking the question: is the biggest advantage due to genetics, or are other variables fueling this advantage?

  To answer this question, it is important to understand many of the most successful trophy Largemouth bass fisheries within each state have some basic characteristics in common. Beginning with good water quality, they are able to 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 fairly simple, right?

 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 production of phytoplankton, which leads to production of forage fish. Simply put, phytoplankton, zooplankton, invertebrates, forage fish, and Largemouth bass rely on optimal temperatures to thrive.

For the purposes of this article, the area of the United States where Florida strain Largemouth Bass are able to 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, as well as reach larger sizes within a growing season. This all leads to growing more pounds of forage fish using plankton compared to water to the northern states.

Forage fish are not always thought of in terms of genetics, but that is a key component as well. Each species of forage has a desired temperature range, as well as lower and upper lethal limits. It just so happens that these southern waters have a genetic advantage with forage species. For example, Threadfin shad are able to 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 good example. Although they do not overwinter throughout most of this Southern Region, they can be stocked earlier in the year, and they die off later compared to cooler climates. This results in a greater biomass of forage produced within a calendar year. With diversity of forage fish, pressure can be relieved off the primary forage fish, the backbone of the food chain for Largemouth bass, bluegill sunfish. The improved performance of forage species provides a big 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 have the ability to stock Threadfin shad; these shad get off to a later start, 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 better understand why the Southern Region produces a greater number of 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.

Stocking F1 Largemouth bass is one solution introduced many years ago to address the inferior bass genetic issue. 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 F1’s have a lethal cold temperature limit, which restricts how far north they can survive in the winter. Although somewhat subjective, F1s 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 F1s spawn with each other. Offspring produced are genetically inferior to their F1 parents, especially regarding top-end growth expectations. As a result, trophy fisheries which have F1s present should take additional management steps to offset this challenge by stocking more F1s from time to time. If you live up north where F1s cannot predictably survive (some states actually outlaw them), keep in mind northern strain bass will often top out 30-50 percent smaller than the Florida strain bass if managed properly. F1s, on the other hand, can get much closer to the size of Florida strain bass, although at the end of the day 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 they should have an 18-24-inch visibility. Pushing waterbodies with this density of plankton will strain water quality, so proper measures need to be taken. Think aeration.

If northern waters are hoping to grow close to the same biomass of forage fish within a calendar year, they need to produce this biomass within a shorter period of time 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 properly, this helps overcome productivity headwinds.

As productivity is increased, it is important to understand proactive water quality management is needed to prevent fish stress as well as a winter fish kill. Some key parameters to pay attention to are dissolved oxygen, pH, alkalinity, total phosphorus, and total nitrogen. In many cases, it can be an expensive endeavor to monitor and keep these parameters within their desired ranges, but 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 has a challenge as well. Surface water temperatures become hot in summer. Hot water may be good for forage production, but is 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 as well as down in this deeper, cooler water is a challenge. As a generalization, Southern Region waters struggle to maintain consistently sufficient oxygen levels due to the hot summertime water temperatures.

It is important to understand 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 growing double-digit bass or that your fishery will be better than someone who lives further north. But yes, it is true that the southern tier of states has a sizable Largemouth bass genetic advantage, coupled with climate advantage for forage fish that results in their fisheries truly 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