Excessive largemouth bass ( Micropterus salmoides ) recruitment in small impoundments leads to density-dependent growth depression, causing populations to have length distributions skewed towards smaller fish. To address this issue, we conducted three trials that evaluated stocking all female largemouth bass (F-LMB) in two small Alabama ponds (0.5 and 2.0 ha) where the drainage basin was isolated. Age-1 fish were individually identified for sex using a micro pipette inserted in the urogenital pore, tagged, and stocked at 38-40 F-LMB/ha into ponds that contained pre-established sunfish ( Lepomis spp.) populations. Female largemouth bass were collected with electrofishing, angling, and rotenone over a 2.5- to 5-year period among the three trials. Sex was correctly identified for 179 of the 180 F-LMB stocked. One male was detected in the first trial which resulted in successful largemouth bass reproduction and this trial was terminated after two years. Growth was rapid the first 2 years after stocking as 3-year-old fish reached an average of 429 to 459 mm and 1.37 to 1.66 kg in all 3 trials. However, 2 years after stocking, growth was nil in the second trial even though relative weights of F-LMB were generally greater than 100. In this second trial, removal of about 30% of the F-LMB inhabiting the pond and stocking small Nile tilapia Oreochromis niloticus (25 - 75 mm) resulted in average weights increasing from 1.30 to 2.34 kg in 1 year. Growth of F-LMB continued in the third trail, and average size approached 500 mm and 2.2 kg three years after stocking. Annual survival rates of F-LMB were high and ranged from 0.78 to 0.93 among the 3 trials. Stocking F-LMB offers an attractive alternative in ponds to create a low density largemouth bass population that displays fast growth and high survival when catch-and-release fishing is primarily practiced.
For more than a century, small impoundments or ponds (<40 ha) have provided recreational sport fishing in the USA. About 4.5 million ponds that cover about 3.0 million ha are found in the contiguous USA [
Largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) are the species most commonly stocked into ponds [
New and innovative approaches are now being used to meet different angler expectations as traditional management of sport fisheries in ponds is changing [
Creating a largemouth bass fishery in ponds where recruitment is limited or is non-existent is an attractive management alternative. Triploid largemouth bass are presumably sterile and have been successfully produced [
The objectives of this study were to evaluate F-LMB stockings in three pond trials. In these ponds, we estimated density, biomass, survival, growth, and body condition (weight:length ratio) or relative weight (Wr) of F-LMB. We also assessed the accuracy of correctly identifying gender of largemouth bass. Our goal was to produce relatively low-density largemouth bass populations that only contained large individuals (memorable length ≥ 508 mm) and displayed Wrs over 100. To obtain this goal, we used an adaptive management approach and attempted to improve growth and size of F-LMB by stocking additional prey fish and removing F-LMB to reduce density as needed.
Largemouth bass brood stock to produce F-LMB was obtained from the E. W. Shell Fisheries Center at Auburn University, Alabama. These brood fish were collected from established populations (>30 years) that are intergrade hybrids between northern largemouth bass (M. s. salmoides) and Florida largemouth bass (M. s. floridanus). Feed-trained largemouth bass fingerlings were stocked into 0.04-ha ponds and fed a 40% commercial protein diet twice a day. One year later at age 1, these fish were >200 mm, and many fish were sexually mature. Females were separated from males by inserting a capillary tube into the urogenital pore and classified as females if eggs or ovarian tissue were detected [
Three trials were conducted in two ponds located at the E. W. Shell Fisheries Center between 2006 and 2013 (
In each trial, F-LMB were periodically collected using DC electrofishing and angling, with most sampling occurring in February-April (spring) and October and November (fall) of each year. Totals of 111, 204, and 52 recaptures of stocked F-LMB were made over time in trials 1, 2, and 3 respectively. Of these fish, 189 were recaptured with angling, 139 with electrofishing, and 39 fish were obtained with rotenone (2 mg/L at 5% active ingredient) when the S-15 pond was renovated at the termination of trial 1 in January 2009. During sampling, F-LMB were measured for TL (mm), weighed (g), and the PIT number was recorded. If multiple recaptures of an individual fish occurred during a sampling season, then TL and weight of the first recapture was used in the analyses. Prey fish, including bluegill, redear sunfish (Lepomis microlophus), golden shiner (Notemigonus crysoleucas), threadfin shad (Dorosoma pentenense), and Nile tilapia (Oreochromis niloticus) were not collected, but occurrence was noted. In trial 1, golden shiners were stocked into this pond 9 months after F-LMB were stocked (
Growth, in length and weight, and relative weight were plotted using box plots that visualized these distributions over time when at least 8 fish were collected during a sampling event. Growth of F-LMB from age 1 to age 6 was compared to populations from three distinct regions. These included 1) fast-growing female Florida largemouth bass (one SD above mean length-at-age) populations that were aged with otoliths [
Pond (trial) | Area (ha) | Mean (max) depth (m) | Date F-LMB stocked | Density F-LMB stocked (N/ha) | Mean length F-LMB (range) mm TL | Mean weight F-LMB (range) g | Forage fish stockeda (time) |
---|---|---|---|---|---|---|---|
S-15 (1) | 2.02 | 1.8 (4.0) | Oct 2006 | 40 | 317 (265 - 369) | 493 (283 - 725) | 3700 BGS/ha (May 2006) 2200 GDS/ha (Jun 2007) |
S-15 (2) | -- | -- | Mar 2009 | 40 | 221 (194 - 264) | 177 (116 - 267) | 4900 BGS and RES/ha (Feb 2009) 50 TFS/ha (Jun 2011) 13,000 TIL/ha (Jun 2012) |
S-5 (3) | 0.52 | 1.6 (3.4) | Mar 2008 | 38 | 211 (200 - 231) | 158 (124 - 220) | 3800 BGS/ha (Nov 2007) |
aForage fish; Tria1 1―bluegill sunfish Lepomis macrochirus (BGS) 75 - 100 mm TL; golden shiners Notemigonus crysoleucas (GDS) 100 - 125 mm TL; Tria1 2―bluegill sunfish (BGS) and redear sunfish L. microlophus (RES) 75 - 100 mm TL; Threadfin shad Dorosoma pentenense (TFS) 120 - 140 mm TL; Nile tilipia Oreochromis niloticus (TIL) 25 - 75 mm TL; Tria1 3―bluegill sunfish (BGS) 75 - 100 mm TL.
for intergrade northern largemouth bass × Florida largemouth bass females that were aged with otoliths collected from Lake Seminole (Georgia-Florida-Alabama reservoir, data in [
Program MARK [
We ran a series of four general models [
Finally, population and survival estimates computed from POPAN were compared to either the final number or minimum number of F-LMB recovered or observed when these trials were terminated. The instantaneous annual mortality rates (Z) for each trial were estimated from the equation:
where the number recovered were either the final or minimum number of F-LMB obtained or observed at the termination of each trial, number stocked was the number of F-LMB stocked at the start of each trial, and time was the length of each trial in years. Annual survival rate (S) was estimated from:
Annual survival rates were compared between POPAN estimates and the final/minimum number of F-LMB observed at the end of each trial.
A total of 180 presumed F-LMB were stocked in these three trials, and of these fish, we detected only one male that was stocked into pond S-15 during trial 1. In fall 2008, we collected young largemouth bass in pond S-15. Thus, successful reproduction occurred during the second year after stocking in trial 1. We recovered 8.4 kg/ha and 133 fish/ha of age-1 largemouth bass (range 109 - 170 mm TL) during renovation of this pond in January 2009. Otolith examination of some of these longer young largemouth bass indicated these fish were hatched in spring 2008. We recovered 40 presumed adult F-LMB, and dissection showed one of these fish was a male. Prior to 2008, no young largemouth bass were observed while electrofishing in S-15. Likewise, no young largemouth bass were observed while collecting electrofishing samples in trials 2 and 3. Therefore, we correctly identified 99.4% of the F-LMB stocked based the assumption that all stocked largemouth bass were females in trials 2 and 3, and one male fish was stocked and later collected in trial 1. Since this one male fish could be individually identified from the PIT tag number over time, this fish was not included when estimating growth, relative weight, survival, density, and biomass.
Growth was rapid in all three trials during the first 1.5 to 2 years after stocking as age-3 F-LMB reached an average of 429 to 459 mm TL and weights of 1.37 to 1.66 kg (
This weight loss of F-LMB coincided with successful largemouth bass reproduction in spring 2008. The largest F-LMB produced in trial 1 was 485 mm TL and 2.27 kg, and was an age-3 fish (
In trial 2, growth of age-3 to age-4 F-LMB was nil 2 to 3 years after stocking and Wr declined during this time (
In contrast to other trials, F-LMB growth in trial 3 continued to be relatively fast after age 3; average fish size at age 4 was 485 mm TL and 2.12 kg, 3 years after stocking (
In all three trials, F-LMB grew faster than largemouth bass females collected in Lake Seminole and nine Alabama reservoirs (
Apparent annual survival rates of F-LMB were 0.78, 0.86, and 0.93 in trials 1, 2, and 3, respectively (
Average annual survival rates estimated by POPAN were similar to those survival rates computed from either recovered fish in each pond or the minimum number of unique individuals captured at the end of each trial. Rotenone was applied to terminate trial 1 and over a 3-day pick up, 39 F-LMB were recovered (
Density of F-LMB in these ponds was obviously inversely related to survival as highest densities over time were observed in trial 3 and the lowest in trial 2 after 15 F-LMB were removed three years after stocking (
In trial 3, F-LMB biomass was 55 kg/ha two years after stocking, and biomass remained relatively constant at 62 - 65 kg/ha three to five years after stocking, suggesting F-LMB carrying capacity was reached.
In two of three pond trials, we successfully established pure F-LMB populations and largemouth bass reproduction was not observed. The success of creating a non-reproducing largemouth bass fishery in ponds with female fish depends on correct sex identification of stocked fish and isolation of the drainage basin so males cannot enter the pond. We successfully sexed 99.4% of the largemouth bass examined. Sex was correctly identified for 97% of fish examined with a catheter [
The consequences of imperfect gender identification can be severe. In trial 1, the presence of at least one male fish allowed successful reproduction and resulted in a decline of about 20% in weight of F-LMB in less than one year. We recovered 133 age-1 largemouth bass/ha and this density was about three times higher than the density of age-1 F-LMB originally stocked into our experimental ponds. Without reducing the abundance of these small largemouth bass and/or stocking additional prey fish, we suspect that growth of F-LMB would not have continued over time in trial 1.
Trial, stocking and termination date | Numbera (95% CI) | Apparent annual survival (φ ± 95% CI)a | Final or minimum (min) number observed | Annual survival |
---|---|---|---|---|
Trial 1 Oct 2006 stock | 79b (NC) | |||
0.78 (0.71 - 0.83) | ||||
Jan 2009 terminate | 42 (34 -50) | 39 (final) | 0.75 | |
Trial 2 Mar 2009 stock | 80 (NC) | |||
0.86 (0.82 - 0.89) | ||||
Spring 2012 | 50 (44 - 57) | 42 (min) | 0.81 (min) | |
not estimatedc | ||||
Spring 2013 terminate | 26 (16 - 35) | |||
Trial 3 Mar 2008 stock | 20 (NC) | |||
0.93 (0.86 - 0.96) | ||||
Spring 2013 terminate | 14 (10 - 17) | 13 (min) | 0.92 (min) | |
aestimates made with POPAN. bone fish of the initial 80 fish stocked was collected at termination and was found to be a male. cnot estimated as 15 F-LMB were removed from this trial in Spring 2012.
Trial and model | AICc | ΔAICc | Weight AICc | Model likelihood | Number parameters |
---|---|---|---|---|---|
S-15 trial 1 | |||||
ρ (t) φ (.) | 306.80 | 0.00 | 0.78 | 1.00 | 6 |
ρ (t) φ (t) | 309.34 | 2.54 | 0.22 | 0.28 | 8 |
ρ (.) φ (t) | 375.49 | 68.69 | 0.00 | 0.00 | 5 |
ρ (.) φ (.) | 387.77 | 80.97 | 0.00 | 0.00 | 3 |
S-15 trial 2 | |||||
ρ (t) φ (.) | 297.61 | 0.00 | 0.72 | 1.00 | 6 |
ρ (t) φ (t) | 299.54 | 1.93 | 0.28 | 0.38 | 8 |
ρ (.) φ (t) | 329.26 | 31.65 | 0.00 | 0.00 | 5 |
ρ (.) φ (.) | 334.90 | 37.29 | 0.00 | 0.00 | 3 |
S-5 trial 3 | |||||
ρ (t) φ (.) | 134.23 | 0.00 | 0.99 | 1.00 | 8 |
ρ (t) φ (t) | 144.18 | 9.95 | 0.01 | 0.01 | 12 |
ρ (.) φ (.) | 166.64 | 32.41 | 0.00 | 0.00 | 3 |
ρ (.) φ (t) | 171.65 | 37.42 | 0.00 | 0.00 | 7 |
Overall annual survival rates among our three trials averaged 0.86; thus annual mortality (AM) was 0.14, and since fish were not harvested, the average instantaneous natural mortality rate (M; M = 1 − eAM) was 0.15 (range 0.07 to 0.25). Based on high recapture rates and either recovered or minimum number of fish observed at the end of each trial, this low mortality estimate is likely very accurate. Data or published estimates of M for female largemouth bass currently do not exist. Analyses and reviews of mixed-sex largemouth bass population demographics in larger southern USA water bodies [
Although Wrs over 100 are typically considered good body condition and are often related to faster growth [
The reduction in density of F-LMB and stocking additional prey fish in trial 2 resulted in a nearly a two-fold increase in weight of F-LMB after only one year. This suggested that possibly lower F-LMB stocking densities and stocking additional prey fish will increase growth rates and maximum size of F-LMB. In a newly renovated impoundment (43 ha) in Georgia, 13 F-LMB・ha−1・yr−1 were stocked the first two years (lower than the rates we used) and over 1 million prey fish of varying sizes and species were added over time [
In a moderately productive pond, about 50 kg/ha of largemouth bass was considered a reasonable maximum biomass [
In these experiments, we attempted to reproduce actual pond management practices. Thus, forage fish were added, F-LMB removed, and ponds fertilized as needed based upon performance of each trial towards attaining our objectives through this adaptive management strategy. This was similar to the process undertaken by many private pond owners, consultants, and state fish conservation agencies who manage fishery resources in ponds [
Stocking and maintenance of all F-LMB populations offers an attractive alternative to create low-density, fast-growing, quality largemouth bass fisheries in ponds. Based on our previous research [
Funding for this project was provided by a gift from W. R. Ireland to the School of Fisheries, Aquaculture, and Aquatic Science. Pond fertilizer was kindly provided by Southeastern Pond Management, Calera, Alabama. E. Peatman conducted genetic analysis to classify F-LMB and M. Catalano assisted with Program MARK analysis. J. Slipke and T. Bonvechio provided comments to improve this paper. A host of former and current Auburn University students and staff assisted with field collections.
Michael J. Maceina,Steven M. Sammons,Ronald P. Phelps, (2016) Evaluation of Stocking All Female Largemouth Bass (Micropterus salmoides) in Alabama (USA) Ponds. Natural Resources,07,315-325. doi: 10.4236/nr.2016.76027