Selective Largemouth Bass Harvest: Advanced Strategies

Harvest is one of the most important techniques that can be used in the management of bass in private lakes and ponds. Many lake and pond owners often misunderstand the concept of harvest. Although lake management publications will often recommend removing 15 to 30 pounds of bass per surface acre, depending on the fertility of the lake, removing four 5-pound bass does not have the same effect as removing 25 bass that average .8 pounds each. The key to the success of bass harvest is understanding which sizes of bass need to be removed, and why. This is what many management biologists call “selective” bass harvest.

Within the southeastern United States, most bass become sexually mature at 1 year of age and a total length of approximately 8 inches. Largemouth bass typically begin spawning as early as March and spawn through June, although the peak of the spawn may occur during April. In most lakes or ponds where there is not an excessive population of golden shiners, 3- to 5-inch bluegill or extreme turbidity (muddy water), bass will successfully produce many more fingerlings than are necessary for replacement of those adults that are caught and those that die of natural mortality. As a pond ages, there may be two to five or more age classes of bass that can spawn each spring. Hence the basis of the biggest problem of managing bass in private waters…overpopulation of small bass.

Overpopulation of Largemouth Bass

More than 85 percent of lakes and ponds that are checked by private and state fisheries biologists are crowded with small bass. This is caused by two primary factors, successful annual bass reproduction and survival, and the lack of adequate bass harvest.

Why is this a problem, won’t these small bass eventually grow into big ones? The answer to that question is No! The reason is that the more small bass that you have the less food that each one has to eat and the slower their growth. Bass that are 12 inches long are not “yearlings” but may actually be 2 or 3 years of age, or even older. How do we know this, you may ask? There have been many research studies that have actually aged these bass through studying the age marks in scales and in the ear bones, called otoliths. These techniques show not only how old a bass is, but also its rate of growth since birth.

As a new pond or lake begins to age, especially beyond year three, food of the size necessary to grow larger bass typically begins to disappear. Although there may appear to be a lot of food in the form of small bluegill, this is not the size forage that grows big bass. The forage fish (primarily bluegill) are continuing to reproduce; however, most of the small bluegill are consumed by the myriad of small bass before they reach a size that larger bass need for growth. Although larger bass often have to eat small bluegill or other forage, the energy they gain by catching a small bite is not enough to make them grow.

Selective Largemouth Bass Harvest

It should be obvious by now that if small largemouth bass are a problem in retarding the growth of larger bass, then we need to make a concerted effort to remove small bass. We should select for the size and number of largemouth bass that need to be removed.

How do we determine what our selective bass harvest should be? The best method is to conduct an electrofishing balance check of the fish population, to determine the relative numbers and sizes of food fish and the numbers and sizes of largemouth bass in the population. In addition, fisheries professionals can determine the relative weight or condition factor of each bass in the sample, noting whether it is above or below average in its weight. This gives both you and the fisheries biologist a base line of data to determine which sizes of bass are most numerous and which sizes are thin, or without adequate food. We can now decide, based upon actual data, which bass should be selected for harvest.

Now the work begins! Not only do you have to be aware of the new selective bass harvest, but also you must convince your fishing companions of the importance of harvesting fish in this selected size group. You can no longer accept the standard response to your fishing questions, such as: “Al and I had a great day. We caught about 40 bass but we didn’t keep any of them. You know we just didn’t have time to clean them and besides, we forgot our cooler and our filet knife. You know that Francis and the kids don’t really like to eat bass, especially since that time I burned the grease in the kitchen. We almost never got that smell out of the house.”

It is difficult to manage a lake for quality largemouth bass fishing with friends like that. You can make rules, however, that if they don’t help with the selective harvest, they do not get to fish. Those of you who recognize the importance of selective bass harvest and obtaining annual harvest goals will be rewarded by outstanding bass populations and fishing opportunities. In typical situations, the majority of bass fishing occurs during the spring. This is a wonderful opportunity to employ an advanced selective harvest technique that will result in even better fishing for larger bass.

Advanced Techniques for Selective Largemouth Bass Harvest

It is true that the majority of largemouth bass weighing more than 3 pounds are females and that 99 percent of bass larger than 5 pounds are females. If you want to increase the percentage of large bass in your lake, you should attempt to increase the percentage of females in the population. How do you accomplish that? Remove as many males as possible while you are fishing. Remember that most of the fishing effort and catching occurs during the spring, when it is relatively easy to distinguish males from females.

During the spring, male bass are more vulnerable to angling as they are the first ones on the shoreline, looking for nesting sites and then building nests. Males become much easier to catch during the spawning season, as they are aggressively defending their nests and guarding the schools of newly hatched fry. During the pre- and post-spawn, males and females are more accurately identified by physical characteristics.

Physical Characteristics of Male and Female Largemouth Bass During the Spring Season

Females will typically have a swollen or fat belly before they spawn, but in lakes where food is plentiful, so will males. Although this is the first observation we make, it is not an accurate method of determining sex. Look more closely at the scaleless area around the vent, which is located at the posterior portion of the belly. This area is aptly called the urogential opening, because there is a vent or opening for excretion of wastes and an opening for extrusion of sex products. This scaleless area around these vents is shaped differently for males and females.

Hold a bass you catch during the spring on its back, belly skyward. Look carefully at the area around the vent that has no scales. The area will be almost perfectly round for males and oblong or pear shaped for females. Examine several bass and closely observe the opening toward the tail, this is where eggs are extruded by the females, and milt by the males. Is this opening reddened or swollen? If so, it is very likely a female. This swollen area on females is called the genital papillae, and it will remain red and distended prior to spawning and for many weeks after spawning. Bass do not deposit all of their eggs during their first spawning attempt and will remain ready to spawn again for a month or more after their first spawn.

Males do not have a genital papillae and their vent is seldom red and almost never swollen. Males will often exude a small amount of milt if pressure is applied with the thumb from the top of the belly toward the vent. Look very carefully and you can often see a tiny amount of white liquid accumulate around the vent. This will often start pre-spawn and last until the spawning season is through.

Study the photos in this article and you will be able to sex bass well enough to influence the percentage of females in your lake. If you are going to selectively harvest bass during the spring, you can positively influence the population of your lake by harvesting as many males as possible. You will not harvest too many males. Do not fret over harvesting an occasional female, harvest as many males as you can!! This technique will work for you only in the spring. It is possible to change the sex ratio of your bass population from 50% females to 85% females by harvesting males.

Barry W. Smith is a Certified Fisheries Scientist.