BY BOB WATTENDORF, WES PORAK and RICK STOUT • FOR FLORIDA TODAY • July 12, 2009
Truth is — it isn’t that simple. Florida Fish and Wildlife Conservation Commission (FWC) biologists, as well as other fishery research experts, have understood for years that stocking fingerling bass (1 inch to 1.5 inches long) rarely improves fishing. However, the FWC now appears to be on the brink of a breakthrough.
When Richloam Hatchery in Sumter County was renovated, it was reborn as the Florida Bass Conservation Center (FBCC). Among the new roles and challenges was to expand on pioneering research done by FWC biologists that enable scientists to produce larger advanced fingerling bass (about 4 inches long).
There were always occasions when stocking fingerling bass worked, and the FBCC continues to provide fish for those situations. For example, stocking fingerling bass into a new reservoir or community pond built for that fishing, or into a lake following a drought, a fish kill, or habitat restoration program can restore a population more quickly than natural reproduction.
However, making bass stocking a more effective management tool in other circumstances requires larger hatchery fish, so they can eat a greater variety of prey. Being bigger also is an advantage because fewer predators can eat them.
But the problems have been significant. First, largemouth bass are typically spawned naturally in hatchery ponds because they don’t respond well to hormones, such as those used to spawn striped bass.
Additionally, small bass are cannibals, and don’t like artificial foods, such as those fed to catfish and trout. Therefore, bass were historically grown in fertilized outdoor ponds with lots of zoo plankton (tiny floating animals such as insect larvae). Predators, including minnows, insects and frogs, ate the eggs and baby fish. As the young bass grew larger, other predators such as birds began feasting on them where they concentrated in outdoor ponds.
The FBCC was designed to intensively culture largemouth bass indoors using state-of-the-art technology to avoid their demise by predators outdoors. The FBCC has the potential to produce more than 1,000,000 advanced fingerling largemouth annually.
Through research, scientists found a way to trick bass fry into eating artificial food.It was discovered that by crowding fry together and feeding them live brine shrimp (the size of a gnat) they’d go into a feeding frenzy and be less choosy in what they ate. That allowed researchers to mix in artificial food that was about the size and color of the brine shrimp. Once the bass fry began eating the artificial food, it was easier to progressively train them to take bigger pellets as the bass grew in size.
Unfortunately, during the 1990s, survival of pellet-reared bass was low once stocked into Florida lakes. Liver disease and other problems were linked to poor nutrition. FWC personnel worked with a university nutritionist to develop an artificial diet similar to a bass’ natural diet. The custom feed has more digestible fats and appropriate vitamins that have virtually eliminated liver disease in hatchery bass.
Although vigorous, healthy hatchery fish should survive better in the wild, resolving the diet problems led to another concern — domestication.Research showed that pellet-reared largemouth had difficulty capturing prey in the wild. To reduce this problem, largemouth bass are now fed live fish at the hatchery for a week before stocking.
A lack of experience avoiding predators also may reduce survival, so researchers are attempting to teach hatchery bass to stay away from things that might eat them.
Other research has improved culture conditions, fish health management, handling and hauling protocols. Now scientists are comparing survival rates between hatchery fish that are simply stocked at a boat ramp in the traditional manner, versus those distributed into vegetated habitats around the lake, so they are more dispersed and avoid predators more easily.
The time of year when fish are stocked also is important. Bass and other fishes, invertebrates and amphibians typically reproduce at a relatively specific time, often triggered by seasonal factors such as water temperature, day length, lunar cycle and water levels. In this way, nature provides bass with the correct size prey for the young to get a fast start on life. If hatchery fish are stocked too early, prey may not be available, and if stocked too late prey may be too big — and even turn the table eating bass fingerlings.
This occurs earlier in the southern end of the state compared to the Panhandle. Moreover, there is evidence that bass, such as other naturally evolved animals, have adapted genetically to these subtle differences, so it is important fisheries managers deal with these unique stocks differently so we don’t adversely affect the gene pool. That’s where the ability to adjust water temperatures in the spawning areas at the FBCC comes in, by allowing offspring from parental fish from different areas to be ready for stocking at the most opportune moment.
Advanced fingerling largemouth reared in ponds on live aquatic organisms and stocked into Gadsden County’s Lake Talquin fed on fishes more successfully and grew faster than their wild counterparts during their first year of life in the reservoir. At the end of the first year, hatchery fish composed 40 percent of the bass that survived from that year’s spawn during a year when 25 fish were stocked per acre.
Five years after supplemental bass stocking, hatchery fish accounted for 20-27 percent of bass caught in tournaments. Research is being conducted in Lake Talquin to determine whether pellet-reared hatchery bass will survive as well as hatchery fish reared on live feed.
The Lake Talquin study has provided optimism that stocking advanced sizes of largemouth bass at the appropriate time will become a more widespread and successful management tool. Information gained from research and adaptive management is critical to long-term success of bass stock-enhancement programs. Specific spawning strategies are being used to protect the genetic integrity of Florida bass populations.
