Sportfish
FWRI researchers have completed a four-year study looking at the consequences of bed fishing.
- The first two years were completed in hatchery ponds at the Florida Bass Conservation Center.
- The Last two years were completed in small natural lakes in Ocala National Forest.
- Bass were tracked genetically and each nest was marked and observed.
- Nests were fished and caught bass were safely stored away for 60 minutes before being returned.
- The results show that bed fishing does not significantly impact the numbers of young bass entering the next generation.
- 30% of all wild beds succeeded whether they are fished or not.
Over the last four years, Florida Fish and Wildlife Conservation Commission (FWC) biologists studied the effects of bed fishing on Florida’s Florida bass populations. This topic has been stressed by the angling community, and freshwater fisheries researchers were more than happy to tackle this hot-button issue.
Bed fishing is the practice of fishing bass nests in the spring. Nests can typically be seen from the surface as cleared patches near structure. Male bass instinctively defend their nests, giving anglers a higher chance of fishing success. However, while the adults are off the nest, predators such as bluegill and other panfish eat the eggs and bass hatchlings. The debate over this fishing tactic is whether or not this time taken away from the nest, sometimes hours in tournament conditions, is negatively effecting Florida’s bass populations.
The study began at the Florida Bass Conservation Center near Webster, FL. Each mature bass received a tag and fin clipping for identification and tracking their parental contribution using genetic analysis. In preparation for the bass, hatchery staff placed brush and concrete blocks in the ponds for added spawning habitat along with a stocked fish community to provide food for the bass and nest predators and to simulate a natural water body as best as possible. After the fish were acclimated to the controlled hatchery ponds, biologist performed snorkel surveys to count, mark and track the bass beds. After beds were located, biologists collected five to ten eggs from each active nest for DNA analysis. Using the DNA data from eggs on a nest, biologists tracked how many times each individual male and female bass spawned throughout the spring.
Half of the ponds were fished and caught bass were removed from the nesting area for one hour to observe the impact. After that hour the fish were returned to the pond safely. The other half of the ponds were never fished and only observed on schedule. In the fall, the ponds were drained and all the fish collected. Using genetic analysis of fin clips taken from all young bass documented during the year and comparing it to the known adult bass in the pond, biologists identified which mature males and females contributed to the year class produced. With the angling data, biologists also determined if fish that were caught during the study successfully contributed young bass or see if it was only fish that were not caught that contributed.
This study was repeated with slight alternations in small natural lakes in the Ocala National Forest over the next two years to look specifically at individual nest success rates in the wild.
After four years of research, biologists found that bed fishing has very little impact on how successful individual nests are or the numbers of next generation of bass produced. Fished or unfished, only 30% of all wild bass beds succeeded in this study. The only effect bed fishing had was under high fishing pressure. Under high angling pressure fish may not spawn as many times as unfished populations, but this result was only seen in the relatively small (one acre) hatchery ponds. The number of young bass produced was still unaffected and even bass caught multiple times went on to contribute as much as fish that were never caught. FWC freshwater fisheries researchers would like to thank the many anglers who have requested this study. FWC works for you as much as they work for Florida’s fish and waterways.
Researchers experiment with new hatchery procedures to better prepare young Florida bass for the perils of the wild
As Florida's premier freshwater sport fish, the Florida bass is the central figure in a black bass fishery that generates more than $1.25 billion annually for the state. Maintaining and improving this valuable resource is a continuing effort that relies in part on supplementing wild stocks with hatchery-raised bass.
The FWC's Fish and Wildlife Research Institute (FWRI) evaluates these stocking programs and researches ways to improve them. In recent studies, biologists from FWRI's Eustis Fisheries Research Laboratory collaborated with researchers at the Florida Bass Conservation Center, the FWC's fish hatchery in Webster, to address some of the challenges of introducing hatchery-raised young bass into the wild.
Researchers have found that stocked bass have difficulty adjusting from feed pellets at the hatchery to live prey in the wild. They also typically lack the predator avoidance and survival skills of wild fish.
Biologists documented this vulnerability in a study at Lake Carlton in the Harris Chain of Lakes (Lake County). They tracked young hatchery bass and wild bass with radio telemetry to compare their behaviors. The researchers found that hatchery bass tended to wander away from cover more often than wild bass. Failure to avoid predators, including birds, was apparent from the radio tags that turned up on shore under nests, in neighboring Lake Beauclair, and even inside a live double-crested cormorant. Findings also showed that neither wild nor hatchery bass showed a preference for specific vegetation for cover.
Now researchers are adding predators and live prey to hatchery ponds, conditioning young bass to forage and avoid predators before entering the wild. Early results from this study have been encouraging. Conditioned fish tend to outgrow and survive other hatchery bass, indicating both improved foraging and avoidance of predators.
Additional research is under way to evaluate other aspects of the hatchery and stocking process and ensure that survival rates for stocked bass continue to improve, keeping the Florida bass abundant for Floridians and visiting anglers.
This study assessed the effects of a gizzard shad removal project on redear sunfish populations in the Ocklawaha Chain of Lakes
In 1993, the St. John's Water Management District (SJWMD) began a commercial shad gill netting program on Lake Apopka, which was monitored by the Florida Fish and Wildlife Conservation Commission (FWC). The SJWMD claimed that gizzard shad (Dorosoma cepedianum) resuspend phosphorus from the lake bottom into the water column. Resuspended phosphorus occurs when shad eat and disrupt the bottom, which causes the sediment and the phosphorus particles to suspend into the water column after they had previously settled. The resuspended phosphorus is then used by planktonic algae, resulting in excessive algal blooms.
The program later expanded to Lake Griffin near Fruitland Park in February 2002. During the winter of 2003-2004, approximately 20,000 redear sunfish (Lepomis microlophus) eight-inches or larger in length were caught in gill nets deployed for harvesting gizzard shad. Therefore, a study began in May 2004 to learn if commercial gill net harvest of gizzard shad could impact redear sunfish populations on the Ocklawaha Chain of Lakes (Lake County, Florida). Although the Lake Griffin redear sunfish population was not examined prior to gill-net operations, current studies would determine redear sunfish population parameters following three years of gill netting. Gill-net use is scheduled to be suspended on Lake Griffin for the next several years. After the suspension of gill-net use, biologists will then analyze changes, if any, to the redear sunfish population.
Before biologists can attempt to assess impacts on redear sunfish, some preliminary data must be collected to learn more about the fish population. Basic characteristics of interest are abundance (index of how many fish are in the lake), growth (how fast the fish are growing), and condition (how heavy they are for their size).
Electrofishing is a method often used to obtain this information. This practice allows fish to be collected, measured, and released unharmed. Redear sunfish were collected from Lake Griffin between May 18 and July 1, 2004 by using a standard electrofishing technique drafted by the FWC. All redear sunfish were measured and weighed. A subsample was then collected to determine age and gender.
Electrofishing catch rates for Lake Griffin were low, as 36.3 hours of sampling were needed to collect 471 redear sunfish. Redear catch rates, which measure the number of fish collected per hour of sampling, were 13 fish an hour for all fish and eight fish an hour for fish at least six-inches in length. These values were low compared to a recent University of Florida study of 60 lakes in Florida, which reported an average catch rate of 49 fish an hour. In a FWC statewide database of 35 lakes, the average catch rate was 56 fish an hour. Therefore, the Lake Griffin redear population in the spring of 2004 was estimated to have relatively low abundance compared to other systems in the state.
To assess the condition of fish in a population, we use a measure called relative weight (Wr). Relative weight is the ratio between the weight of a fish and a standard weight obtained from many other populations. It is presented as a percentage, and the higher the value, the better the fish's condition relative to other populations. The average Wr for Lake Griffin redear sunfish was 107 percent, which is average for similar systems in the FWC database but slightly higher than the state mean of 92 percent. The Wr values were particularly high for Lake Griffin redear sunfish that were larger than six-inches in length, which indicates an abundant food supply for adult sunfish. However, relatively lower values were found for smaller individuals, which may indicate that there is a food shortage problem for smaller fish.
Age and length information was used to calculate total annual mortality (A), which is the combined number of fish lost annually to fishing mortality (harvesting of fish) and/or natural mortality (weather, disease, predators). Total annual mortality for redear sunfish in Lake Griffin was 60 percent as compared to the statewide average of 47 percent. The slightly higher than average total annual mortality rate for the Lake Griffin redear sunfish population may be the result of a variety of factors, including increased fishing mortality (commercial and recreational) of older fish and the lack of fish older than four-years in the electrofishing sample.
We also examined the growth of individuals in the population. Redear sunfish grew rapidly at Lake Griffin, particularly for fish at least two-years old. The mean size for fish ages 2- to 5- years old was substantially higher than those of the FWC statewide redear sunfish database and previous samples collected in 1997 from Lake Griffin. Unlike 1997 when first-year growth was found to be limited, recent data indicated the most growth generally occurred during the fish's first year.
From the information we have gathered, we have determined that there is a low abundance of redear sunfish in Lake Griffin, but the growth and condition of these fish were generally good, particularly for adult fish. Low condition values for smaller individuals may indicate that there is a problem in the amount of prey available for these fish.
Similar data were collected from other lakes in the Ocklawaha Chain of Lakes, including Lakes Dora, Beauclair, and Eustis. Additional sampling is scheduled for May 2007. Lakes Dora and Beauclair were opened in March 2005 to commercial harvest of gizzard shad, and Lake Eustis will serve as a control (no harvest) lake. This information will allow biologists to examine redear population dynamics prior to gill net fishing and help biologists determine if and how the gill-net fishery for gizzard shad is impacting the redear population in these lakes.