This will not come as much of a surprise to most experienced bass fishermen.  The largest bass that come out of California and Florida are females that are caught just prior to spawning.  When a pair of bass spawn, they produce a brood of fingerlings consisting of an equal number of males and females, or a 50:50 sex ratio.  This means that only half of these fingerlings have the potential to reach trophy size.  In your lake you are feeding and growing a population of 50% males that will rarely have the potential to grow larger than 5 pounds.  The other downside of this equation is that these males are eating forage (food) that could be used to fatten the females.

Steve Honaker holds a 10-lb female bass taken from a lake near Montgomery, AL Lunkers like this one can be much more common in lakes stocked with all-female bass.

Another big advantage to having a population of all females is that since there is no spawning and the bass numbers are fixed, they tend not to overgraze the food supply. Barry Smith, my partner at American Sport Fish, was recently a speaker at a Bass Symposium for lake owners.  Barry told the group, “the most common problem we see as lake consultants are lakes that are overcrowded with undersized or stunted bass. This is due primarily to the landowner not harvesting enough bass in the early years after stocking and the bass numbers build up, eat most of the forage and then quit growing.”
If we have all females, the lakes do not get overcrowded, there is a surplus of food and the bass get fat and happy without having to expend a lot of energy hunting down their prey.
The Texas Parks and Wildlife Department has undertaken the most aggressive bass management program in the country.  It has invested heavily to establish excellent physical facilities and a competent staff of researchers to explore new avenues of improving bass fishing.  One of these researchers, Dr. Gary Garrett, started working on the concept of all-female bass in the 1980’s.  “One of our goals was to develop a technique to produce large numbers of 100 % female bass.  These could then be stocked into reservoirs to increase the potential of trophy production,” said Garrett.

Gergely Uberpacker , a graduate of St.Stephen’s University in Godollo, Hungary, is conducting genetic research on largemouth bass at American Sport Fish.  Uberpacker hopes to have a limited number of all-female bass available for American Sport Fish during the spring of 2009.

Dr. Garrett and his colleagues at Texas Parks and Wildlife’s Heart of the Hills Research Station were successful in producing 100% female bass by treating newly hatched fry with a female sex hormone.  This shifted the normal sex ratio of 50:50 to one of 100% females.  However, the FDA would not allow fish that had been treated with a hormone to be stocked in public waters, since they may be consumed for food.
Several other researchers obtained results similar to the Texas study.  Dr Ron Phelps at Auburn University’s Department of Fisheries also produced 100 % female bass by feeding fingerlings a feed coated with a female hormone.  Dr Ronnie Gilbert of the University of Georgia produced all females by immersion of bass fingerlings in aquaria that had been treated with female hormones.  “We know that these hormones are completely metabolized and no residual hormones remain in the treated bass long before they reach a harvestable size.  However, to have this treatment approved by the FDA would cost millions of dollars and several years to complete the study,” says Dr Phelps.

Linda Jones of Woodbine, Ga. is shown with an 8- lb bass that was collected in June from a lake stocked with all females.  Notice that this female appears to still have her eggs even though it is two months past the normal spawning season. Because there is no spawning, these bass retain their eggs and slowly reabsorb them throughout the summer.

There is a method to produce all-female progeny that have not been exposed to hormones.  This technique has been used at Kentucky State University to produce all- female black crappie.  To accomplish this, 2-inch crappie were treated with a male hormone to produce 100% males.  When these fish were sexually mature the researchers had a group of fish that were 50% normal males and 50% that were females that had been sex-reversed to males. These sex-reversed males produced testes and viable sperm.  Sperm from a sex-reversed female was used to fertilize eggs from a normal female, thus producing 100 % female offspring.  The offspring had not been exposed to hormones.  The difficult part of this equation is identifying which are normal males and which are sex-reversed females.   Trust me, it is not as easy as it sounds.
What kind of growth can you expect if you have an all-female bass lake?  We are beginning to get some feedback from a few lakes that we at American Sport Fish have stocked with all-female bass.  To obtain our all females we examined sexually mature bass during January through March prior to spawning.  These fish were tranquilized and a small glass tube was inserted into the urogenital opening.  If we observed eggs, it was a confirmed female.

Female largemouth that have a surplus of forage are capable of reaching 6 pounds or more in two years.

These bass were then stocked at a low density in lakes that had been stocked with forage for several months.  Scott Robinson, fisheries biologist with the Georgia Department of Natural Resources, stocked some of these bass into a private lake south of Atlanta.  “When I picked up the bass from American Sport Fish they weighed 1 to 2 pounds.  I went back to this lake and electrofished it two years later.  I turned up one fish that was 9 _ pounds,” Scott said,  “That is about as fast of growth as you can expect.”
My partner, Barry Smith had similar results.  “I stocked some females that weighed about 1/2 pound in a private lake with heavy forage and no bass.  One year later I went back to this lake and sampled the fish with an electrofishing boat. I turned up bass that weighed 4 1/2 pounds.  That is a true 4-pound gain in one year,” Barry said.

Allen Forshage, Director of the Texas Park and Wildlife Freshwater Fisheries Center and Share a Lunker Program, talks of a 14-pound female brought to the Freshwater fisheries Center in Athens.  “One year later, through our care and feeding, that fish weighed more than 18 pounds.”
There is speculation among fisheries scientists as to how many trophy bass can be produced in a lake of all-female bass.  Just keep in mind that these females are fertile, and hope some good-hearted neighbor does not donate a male to the lake.

Don C. Keller is a Certified Fisheries Scientist and Co-Owner of American Sport Fish. He has authored numerous publications relating to bass research and management.