Bluegill Population Research in Northeast South Dakota
Background for Research
Bluegills are an important sport fish in select northeast South Dakota lakes. 
Information concerning bluegill population dynamics is lacking.
Periods of high harvest have raised concern from anglers about the size of fish available for harvest. The impact angler harvest may be having on population dynamics is unknown.
Size structure in bluegill populations is largely influenced by males. Males may be parental males or cuckold males. Parental males typically grow large before maturing, whereas cuckold males mature at a small size.
Cuckold males are either "sneakers" or "female mimics." Sneakers sneak into a nest and fertilize eggs, while the parental male spawns with a female. Female mimics approach the female from the opposite side as a parental male during spawning and fertilize the eggs. Mimics are not chased from the nest because the parental male thinks it is another female.
Four factors have been identified that can result in unfavorable bluegill populations. The factors include 1) overharvest of large individuals, 2) density-dependent growth (high competition for food results in slow growth), 3) social influence (removal of large males leads to earlier maturation of males thus less energy is used for growth, and 4) excess production of cuckold males.
Study Components
Bluegills > 6 inches are tagged in each lake. Tags consist of non-reward tags and $100 reward tags. The tags allow for estimating population abundance and the percentage of the population harvested each year (exploitation). 
An angler use and harvest survey (creel) has been in place at each lake. This survey estimates fishing pressure directed at bluegills, the number of bluegills caught and harvested each year, and the size of bluegills harvested.
A standard trap net survey was completed at each lake and each year of the study. Data obtained in the standard survey will provide information concerning bluegill population size structure, condition, age and growth, mortality, and recruitment.
Information gained from all parts of the study will be used to model bluegill population dynamics and estimate population responses to potential harvest regulations.
Lakes and years
Enemy Swim 2019 – 2023
Clear (Marshall County) 2022 – 2023
Pickerel 2020 – 2021
Reporting Tagged Bluegills
Anglers can report tagged fish online or by calling 605.626.3343.
Physical proof is needed for a reward to be paid. A picture of the tag showing the reward tag number can be included with the online form, or the tag can be presented to South Dakota Department of Game, Fish and Parks (GFP) staff at the Webster GFP office (603 East 8th Ave, Webster, SD).
Anglers are encouraged to leave tags in bluegill that are released so that additional information can be gained from that fish. The tag number should still be reported for fish that are released.
Each reward tag will be paid only once during the study; reward payments will not be made on fish reported after December 31, 2025. Bluegill have been tagged in Enemy Swim (2019-2023), Pickerel Lake (2020 and 2021), and Clear Lake (2022 and 2023) to estimate angler harvest.
Updates
Lake Enemy Swim
| Year | Population Estimate (#) | CPUE (#/net) | %>6 inches | %>8 inches | length at age 4 (inches) | length at age 6 (inches) | % annual mortality |
% Harvest |
|---|---|---|---|---|---|---|---|---|
| 2019 | 18,152 | 62.8 | 17 | 3 | 5.0 | 8.0 | 71.1 | 6.0 |
| 2020 | 21,989 | 46.0 | 19 | 2 | 5.0 | 7.9 | 71.0 | 33.3 |
| 2021 | 65,442 | 85.6 | 67 | 22 | 6.0 | 7.8 | 43.1 | 18.8 |
| 2022 | 20,713 | 43.5 | 65 | 24 | 4.6 | 7.2 | 36.6 | 2.0 |
| 2023 | 14,623 | 121.3 | 41 | 15 | 5.2 | 7.6 | 30.6 | 27.3 |
- Population abundance is moderate to high.
- Size Structure has improved with the percentage of fish greater than 6 and 8 inches higher during 2021-2023.
- Bluegill growth is slow to average. It takes approximately 7 years for a bluegill to reach 8 inches.
- Annual mortality is moderate to high. Few fish exceed 6 years old.
- Angler harvest varied from moderate to low during 2019-2023.
Pickerel Lake
| Year | Population Estimate (#) | CPUE (#/net) | %>6 inches | %>8 inches | length at age 4 (inches) | length at age 6 (inches) | % annual mortality |
% Harvest |
|---|---|---|---|---|---|---|---|---|
| 2019 | 24.5 | 92 | 15 | 8.3 | ||||
| 2020 | 19,066 | 20.3 | 94 | 44 | 8.3 | 63.2 | 57.0 | |
| 2021 | 9,593 | 3.0 | 74 | 20 | 7.8 | 34.0 | 35.0 | |
| 2022 | 1.5 | 28 | 20 | 8.6 | 10 | 59.2 | ||
| 2023 | 9.7 | 10 | 1 | 6.9 | 86.6 |
- Population abundance currently is low.
- Size structure has been low in recent years. Fish born in 2020 dominate the population.
- Bluegills grow fast. At Pickerel Lake, bluegills typically exceed 8 inches during their fourth growing season.
- Annual mortality is high. Few fish exceed 6 years old.
- Angler harvest was high in 2020 and 2021 when quality-size bluegills were available.
Clear Lake
| Year | Population Estimate (#) | CPUE (#/net) | %>6 inches | %>8 inches | length at age 4 (inches) | length at age 6 (inches) | % annual mortality |
% Harvest |
|---|---|---|---|---|---|---|---|---|
| 2019 | 95.3 | 23 | 4 | 5.9 | 8.0 | 63.0 | ||
| 2020 | ||||||||
| 2021 | 51.3 | 85 | 3 | 6.5 | 7.6 | 53.1 | ||
| 2022 | 189,889 | 45.2 | 88 | 2 | 6.1 | 7.4 | 45.5 | 1.0 |
| 2023 | 99,331 | 66.7 | 76 | 4 | 6.5 | 7.1 | 7.0 |
- Population abundance is high.
- Size Structure has improved with the percentage of fish greater than 6 inches increasing, but few fish exceed 8 inches.
- Bluegill growth is slow to average. It takes approximately 7 years for a bluegill in Clear Lake to reach 8 inches.
- Annual mortality is moderate to high. Few fish exceed 6 years old.
- Angler harvest was low during 2022 and 2023.
