Pumpkinseed population characteristics in a Northeast South Dakota glacial Lake

Abstract

Eastern South Dakota represents the western extent of the Pumpkinseed Lepomis gibbosus native range. Lake Enemy Swim, just to the west of the native range, has the highest Pumpkinseed abundance in this region. Information about the Pumpkinseed population characteristics in Lake Enemy Swim could aid in managing the species. Our study objectives were to 1) describe current Pumpkinseed population characteristics in Lake Enemy Swim and 2) examine if they have changed over the last 25 years. We collected Pumpkinseeds in May 2023 with modified-fyke nets and angling and during annual population sampling with modified-fyke nets from 1999–2023. The Lake Enemy Swim Pumpkinseed population is not abundant and has persisted at a low level from 1999–2023. Population size structure was variable but generally trended downward since the early 2000s. In 2023, the maximum estimated age was 8 years, growth was average, with fish attaining 150 mm at age 4, and the von Bertalanffy growth model predicted an asymptotic length of 205 mm. However, since 2015, no fish exceeding 200 mm have been observed. Yearly relative weight (Wr) means generally exceeded 95. In 2023, annual mortality was estimated at 29%, and recent recruitment appears consistent but low magnitude. The Pumpkinseed sport fishery in Lake Enemy Swim is limited due to the low population abundance and small size structure. The recent invasion of Zebra Mussels Dreissena polymorpha may provide a new food source, which could lead to improved growth and size structure. This study provides baseline information concerning a Pumpkinseed population near the western extent of their native range now subjected to Zebra Mussel infestation.

Keywords:

• Pumpkinseed
• Lepomis gibbosus
• population
• management
• South Dakota

Introduction

The Pumpkinseed Lepomis gibbosus is a member of the sunfish family Centrarchidae. It is primarily native to the northeastern United States but introduced elsewhere. Northeast South Dakota represents the western extent of the Pumpkinseed native range, where they are native to the Minnesota River drainage (Bailey and Allum 1962). Pumpkinseeds are generally found in shallow lakes with submerged vegetation (Keast 1978). Young Pumpkinseeds use dense near-shore vegetation, while adults are most abundant in sandy shallow areas (Keast 1978). Young fish use the vegetation to avoid predation, whereas adult Pumpkinseeds are often found in less vegetated areas. Pumpkinseeds are thought to thrive at temperatures between 24° C and 32° C and are tolerant of low oxygen levels (Holtan 1998). Pumpkinseeds are frequently sampled from Lake Enemy Swim in northeast South Dakota, occasionally from Wall Lake in the southeast, and infrequently from other waters. The origin of Pumpkinseeds in Lake Enemy Swim is unknown; there are no records of stocking Pumpkinseeds dating back to 1914.

Pumpkinseed diet varies by age and prey items available. Gastropods make up a large fraction of the adult pumpkinseed diet, but young Pumpkinseeds typically feed on insect larvae, amphipods, and other littoral-zone invertebrates (Osenberg et al. 1992). Pumpkinseeds have enlarged pharyngeal jaws compared to other sunfishes (Wainwright 1996). The robust jaw enables them to produce a bite force strong enough to crush hard-shelled prey. Pumpkinseed pharyngeal jaw size has been found to increase when hard-shelled snails make up a high percentage of their diet relative to zooplankton (Berchtold et al. 2015; Jarvis et al. 2021). Pumpkinseeds will consume Zebra Mussels Dreissena polymorpha, which were recently found in South Dakota, including Lake Enemy Swim in 2022. In Canada, lakes where Zebra Mussels and Pumpkinseeds were present, Zebra Mussels accounted for 68% of Pumpkinseed stomach contents (Colborne et al. 2015).

Across their range, Pumpkinseeds likely serve as prey for many predators, including but not limited to Walleye Sander vitreus, Largemouth Bass Micropterus salmoides, and Northern Pike Esox lucius. Pumpkinseeds dominated Walleye diets in number and weight in a 4.3-hectare pond in Washington, where Walleyes were introduced to control overabundant Yellow Perch Perca flavescens (Bolding et al. 1998). Pumpkinseeds provide angling opportunities where they occur, and anglers generally target sunfish species under the broad categories of ‘sunfish’ or ‘panfish’ of which Pumpkinseeds are included. Pumpkinseeds are often harvested in combination with other sunfish species because many anglers often cannot differentiate between various sunfish species. In Ohio, only 8.3% of 397 anglers correctly identified Pumpkinseeds in their catch (Page et al. 2012). Anglers in the Ohio study most commonly (59.7%) identified the Pumpkinseed as a Bluegill Lepomis macrochirus. In Lake Enemy Swim, increasing numbers of large (≥ 200 mm) Bluegills since the mid-1990s have increased angler interest in the Bluegill fishery (Weimer 2004) and the potential for increased harvest of Pumpkinseeds.

Lake Enemy Swim has the highest Pumpkinseed abundance in South Dakota, but abundance is lower than typically observed in native waters. Outside of a single study completed during 1998–2003 (Weimer and Brown 2006), little is known about the Pumpkinseed population characteristics in Lake Enemy Swim and whether the population has temporally changed. We examined the Pumpkinseed population characteristics in Lake Enemy Swim in 2023. The population parameters we were interested in included relative abundance, size structure, condition, length at capture at age, mortality, and recruitment. Additionally, we were interested in examining if changes have occurred in relative abundance, size structure, and condition over time. Therefore, our study objectives were to describe the Lake Enemy Swim Pumpkinseed population characteristics for 2023 and examine how parameters may have changed over the last 25 years (1999–2023). Gaining an understanding of Pumpkinseed population characteristics could be benefit the management of this species.

Materials and methods

Study site

Lake Enemy Swim is located in northeast South Dakota (Day County). The lake has a surface area of 870 ha, a maximum depth of 8.5 m, and an average depth of 5.0 m. It is mesotrophic, with a highly irregular lake bottom and a variety of habitat types ranging from shallow vegetated bays, deep silty flats, rock shorelines, and points (Weimer 2004). In 1996, 31% of the Lake Enemy Swim basin contained submerged or emergent vegetation (Blackwell 2001). Submerged vegetation (e.g. various pondweeds Potamogeton spp., Coontail Ceratophyllum demersum, Northern Watermilfoil Myriophyllum sibiricum), is common in near shore areas and open water areas are less vegetated. Water clarity is high in Lake Enemy Swim, with Secchi depths commonly exceeding 1 m. The average Secchi disk depths reported by the South Dakota Department of Agriculture and Natural Resources (SDANR 2024; https://apps.sd.gov/NR92WQMAP) for 2020–2023 were 1.38 m (SE = 0.068; 2020), 1.73 m (SE = 0.188; 2021), 1.77 m (SE = 0.175; 2022), and 1.39 m (SE = 0.060; 2023). The lake has a complex sport fish community, including Black Crappie Pomoxis nigromaculatus, Bluegill, Largemouth Bass, Northern Pike, Smallmouth Bass Micropterus dolomieu, Walleye, and Yellow Perch.

Fish collection

Pumpkinseeds for age estimation were collected as part of a project assessing the Lake Enemy Swim Bluegill population using modified-fyke nets and angling in May 2023. Additional fish were collected during the annual South Dakota Department of Game, Fish and Parks (SDGFP 2004) standard fish community survey in June 2023. The time between collections was only a few weeks. Little change in Pumpkinseed lengths between the collections would be expected due to cool water temperatures and the short period between collections. All fish collected for age estimation were brought back to the lab, where they were measured for total length (TL; mm), weighed (g), gender determined, and sagittal otoliths removed. Pumpkinseeds were annually sampled from 1999–2023 during SDGFP standard fish community surveys. Sampling occurred within the timeframe of mid-June to mid-July each year, and effort ranged from 14–18 net nights. The South Dakota standard modified-fyke net (two 0.9 × 1.5-m frames, three 0.9-m diameter hoops, a single throat, a 0.9 × 15.2-m lead, and 19-mm bar knotted mesh) was used to collect fish during the Bluegill project and the annual survey, except during 2016 and 2017. In 2016 and 2017, the recommended North American standard fyke net (two 0.9 m x 1.8 m frames, four 0.8 m hoops, a single throat, 0.9 × 15.2 m lead, and 13 mm bar knot-less mesh) was used. The larger mesh of the South Dakota standard modified-fyke net was thought to contribute to a higher Bluegill size structure in a paired gear comparison between the North American and the South Dakota standard modified-fyke net (Smith 2015). During the Smith (2015) study, too few Pumpkinseeds were collected to compare their sizes between the two net types; thus, we did not make any adjustments for the different net types. Fish collected during standard surveys were also measured for TL (mm) and weighed (g).

Age estimation

Collected otoliths were wiped clean, stored individually in labeled plastic vials, and allowed to dry a minimum of 2 weeks before age estimation. Otoliths were viewed with a stereo microscope (UNITRON Z850; Commack, New York, USA) using reflected light. They were either viewed whole while submersed in water over a black background or cracked in half at the nucleus and placed on end in clay for viewing (Blackwell et al. 2022). A fiber optic filament was used to aid in identifying annuli on cracked otoliths (Long and Grabowski 2017). Because fish were sampled in the spring, an annulus was assigned to the outer edge. Two readers independently estimated ages from the otoliths without knowledge of fish TL or weight. A third reader estimated the ages when the two readers disagreed. A consensus age was obtained for 65 (91.5%) of the 71 Pumpkinseeds collected for age estimation in 2023. Fish that all three readers disagreed on the age were discarded from age and length-at-capture analyses.

Data analyses

Relative abundance of Pumpkinseeds during annual standard surveys was quantified as catch per unit effort (CPUE; number of stock-length [≥80 mm; Gabelhouse 1984] fish per net night). Population size structure was quantified using proportional size distribution (PSD; Guy et al. 2007) for years when a minimum of 20 stock-length fish were collected. Pumpkinseed minimum TLs for stock, quality, and preferred lengths are 80, 150, and 200 mm (Gabelhouse 1984). Body condition was assessed using relative weight (Wr; Blackwell et al. 2000) with annual mean Wr values calculated for stock-length (i.e. ≥80 mm) fish only.

A weighted catch curve (Ricker 1975) was used to estimate total mortality for the 2023 age sample. Residuals from the catch curve were used to assess year-class strength for the 2023 age sample (Maceina 1997). Positive residuals suggest strong year classes and negative residuals suggest weak year classes. Recruitment was assessed for the 2023 sample using the recruitment variability index (RVI; Guy and Willis 1995). Values of the RVI can range from 1 to −1 with values close to 1 indicating stable recruitment. Linear regression was used to assess temporal trends in CPUE, PSD, and Wr across years. Mean lengths at capture at each age were compared between genders with a t-test. A von Bertalanffy growth model was computed using the 2023 mean TL at age for ages 2-8. All statistical analyses were completed with SYSTAT13 (SYSTAT 2009), and an α ≤ 0.10 was used to indicate statistical significance.

Results

In 2023, the annual population sample had a stock-length CPUE of 1.3 (SE = 0.29). Annual stock-length Pumpkinseed CPUE was variable, with values ranging from 0.04 (SE = 0.04; 2007) to 4.04 (SE = 1.89; 2001) for 1999-2023 (Figure 1). Surveys completed from 2001–2005 had the highest CPUE. A significant (F = 3.454; d.f.=1, 23; r²=0.13; p = 0.076) downward trend in CPUE has occurred since 1999. Collected Pumpkinseed in 2023 standard sample ranged in TL from 78 to 192 mm (Figure 2) and had a PSD of 38 (95% CI = 15-61). The number of fish sampled for 10 of the years was below our criteria (≥20 stock-length fish) for calculating PSD. Like CPUE, PSD was variable during 1999–2023, with values ranging from 3 (2010) to 100 (2005; Figure 2). A significant (F = 9.052; d.f.=1, 13; r²=0.41; p = 0.010) downward trend was evident with PSD over time (Figure 3). The mean stock-length Wr in 2023 was 108 (SE = 0.99). Annual mean Wr varied between 94 (SE = 2.82; 2009) and 116 (SE = 1.41; 2020) and no temporal trend (F = 0.895; d.f.=1, 22; r²=0.04; p = 0.354) occurred in annual mean Wr across years (Figure 4).

Figure 1. Mean catch per unit effort (CPUE; number per net) for pumpkinseeds captured in modified-fyke nets fished overnight in Lake Enemy Swim, South Dakota, during annual surveys completed during 1999–2023. The regression line is significant (p = 0.076).

Figure 2. Length frequency distributions of A) pumpkinseed collected during annual South Dakota Department of Game, Fish and Parks sampling, B) pumpkinseed collected for age estimation, and C) age distribution of pumpkinseed collected in the 2023 spring from Lake Enemy Swim, South Dakota.

Figure 3. Annual proportional size distribution (PSD) for pumpkinseeds captured in modified-fyke nets fished overnight in Lake Enemy Swim, South Dakota, during annual surveys completed during 1999–2023. A minimum sample size of 20 stock-length fish was necessary to calculate PSD. The regression line is significant (p = 0.010).

Figure 4. Annual mean relative weight (Wr) for stock-length pumpkinseeds captured in modified-fyke nets fished overnight in Lake Enemy Swim, South Dakota, during annual surveys completed during 1999–2023. The regression line is not significant (p = 0.354).

The estimated annual mortality from the weighted catch curve in 2023 was 28.7% and the estimated annual survival was 71.3% (Figure 5). Recruitment has been relatively stable in recent years but low magnitude. A single cohort (age 7) was missing between ages 2–8 and the RVI was 0.54. Based on the weighted catch-curve residuals, the 2018 cohort (age 5) represents a strong cohort, while the 2016 (age 7) cohort was absent. The other cohorts (ages 2, 3, 4, and 8) had near-zero residual values suggesting average recruitment.

Figure 5. Weighted catch-curve for ages 2–8 pumpkinseeds collected with modified-fyke nets from Lake Enemy Swim, South Dakota in June 2023. The estimates of instantaneous mortality (Z), annual mortality (a), annual survival (S), and the regression p-value and coefficient of determination (r²) are provided.

Pumpkinseeds collected for age estimation ranged in TL from 75 to 195 mm (Figure 2). Consensus ages were estimated for 24 female and 41 male Pumpkinseeds (Table 1). The estimated ages of fish in the sample ranged from 2–8 years (Figure 2), and the theoretical maximum age estimated from the weighted catch curve was 11.1 years. The mean lengths at age at capture in 2023 spanned from 95 mm (age 2) to 190 mm (age 8). Lengths at capture at age were similar between genders except for age-2 fish. At age 2, females were significantly (t = 2.674, d.f.=13, p = 0.019) longer than males. The von Bertalanffy growth model estimated the asymptotic length (L_∞) at 205 mm, the growth coefficient (k) was 0.368, and the theoretical time when the length was 0 (t₀) was 0.394 for the genders combined. In 2023, the estimated time for Lake Enemy Swim Pumpkinseeds to reach 150 mm was 4.0, and 10.7 years to reach 200 mm.

Table 1. Mean total length (TL; mm) at age by gender and combined for pumpkinseeds collected in modified-fyke nets (n = 61) and by angling (n = 4) from Lake Enemy Swim, South Dakota, in the 2023 spring. The standard error of the means is in parentheses, n is the number of fish included for each estimated age, and the resulting p-values from t-tests comparing TL between genders.

	Female		Male			Combined
Age	n	TL (mm)	n	TL (mm)	p-value	n	TL (mm)
1
2	5	106 (7.89)	10	89 (2.37)	0.019	15	95 (3.60)
3	4	108 (4.69)	10	119 (4.23)	0.166	14	116 (3.49)
4			10	156 (4.34)		10	156 (4.34)
5	8	167 (5.19)	10	172 (3.36)	0.435	18	170 (2.93)
6	3	179 (2.67)	1	179		4	179 (1.89)
7
8	4	190 (1.49)				4	190 (1.49)

Discussion

The Lake Enemy Swim Pumpkinseed population is at a lower abundance when compared to the Bluegill population and has persisted at a low density over the last 25 years (1999–2023). Relative abundance peaked in the early 2000s (4.0 fish/net, 2001) and has since trended downward. Weimer and Brown (2006) also noted that the Lake Enemy Swim Pumpkinseed population abundance was low during 1998-2003. The low Pumpkinseed relative abundance may be related to Lake Enemy Swim being outside the native range. At Lake Joslin, Michigan (within native range) higher relative abundance was noted, with trap net catch rates averaging 31 fish per net night from 1998 through 1994 (Braunscheidel and Towns 2017). Similarly, Pumpkinseed fyke net catches at Booth Lake, Wisconsin (within native range) averaged 41 fish per net night (Kubisiak 2005). Pumpkinseed populations in several Nebraska Sandhill lakes (outside the native range) had similar relative abundance to Lake Enemy Swim, with average fyke-net CPUEs ranging from 0.6–7.5 fish per net night (Harrington et al. 2001). In an investigation of 22 small artificial lakes in Illinois, Pumpkinseeds were found in five waters but only comprised a trace (<1%) of the total fish composition by weight in each pond (Bennett 1943).

Population size structure was variable in Lake Enemy Swim, with the highest PSDs occurring in 2000 (PSD = 91), 2005 (PSD = 100), and 2014 (PSD = 80). The observed peaks in PSD were likely related to strong year classes reaching quality length. Random variations in recruitment were found to cause large fluctuations in the PSD of Largemouth Bass in Ohio reservoirs (Carline et al. 1984), and Daugherty and Smith (2012) found strong year classes to improve PSD in White Bass Morone chrysops and Largemouth Bass. Like CPUE, PSD has trended downward since the early 2000s. Pumpkinseed size structure during 1998–2003 was classified as high in Lake Enemy Swim, with PSDs ranging from 71–91 and the PSD of preferred length (PSD-P) ranging from 0–9 (Weimer and Brown 2006). In recent years (2021–2023), the PSD has been substantially lower, ranging from 4–38. Preferred-length Pumpkinseeds (≥200 mm) have not been collected from Lake Enemy Swim since 2016. The asymptotic length was estimated at 205 mm in 2023 and 223 mm in 2003 (Weimer and Brown 2006). The slower growth in 2023 has likely led to the lower estimated asymptotic length and the limited number of fish exceeding 200 mm. Reaching 200 mm may be difficult for Pumpkinseed populations outside their native range. No preferred-length Pumpkinseeds were sampled in seven Nebraska Sandhill lakes having Pumpkinseeds (Harrington et al. 2001).

Pumpkinseed body condition varied over the 25 years (1999–2023) but has generally maintained at a high level (i.e. annual mean Wr > 95). Relative weight is generally viewed as a measure of recent conditions, while growth is an accumulative measure of conditions encountered over a longer time (Blackwell et al. 2000). Lengths at estimated ages in 2023 were substantially lower than those reported in 2003 for ages 2–5 (mean TL at ages 2–5 in 2003 were 142, 169, 185, and 198 mm, respectively) when growth was near the upper bounds for the species (Weimer and Brown 2006). Although Pumpkinseed growth has slowed, it is comparable to other North American and European populations. The mean length at age 2 for Lake Enemy Swim was more than 20 mm greater than the means reported for 15 Ontario waters (Fox 1994) and those reported for 46 North American and 44 European populations (Fox and Copp 2014).

In 2003, the Lake Enemy Swim Pumpkinseed annual mortality rate was estimated at 75% (Weimer and Brown 2006). The estimated annual mortality in 2023 was 29%. We are not sure why there would be this large of change in mortality rates between 2003 and 2023. We observed similar numbers of fish for each cohort at ages 2–5 in the 2023 sample, and the oldest individuals in the 2023 sample were estimated to be 6 and 8 years old, while no fish exceeded 5 years in 2003 (Weimer and Brown 2006). The similar numbers of fish at ages 2–5 and having fish up to age 8, led to a low slope in the catch curve analysis and the subsequent low 2023 mortality estimate. The 2003 annual mortality estimate of 75% (Weimer and Brown 2006) is closer to that reported for other populations. Annual mortality averaged 72% during 1955–1969 at Murphy Flowage, Wisconsin, when fishing was allowed, and 68% in years when no fishing occurred (Snow 1978). In Pennsylvania, annual mortality for Pumpkinseed populations averages 60% (Lorantas and Frick 2018). Without long-term annual mortality data, we are unsure if mortality has changed or if the 2023 sample was an anomaly. We recommend that estimating Pumpkinseed annual mortality becomes a part of the SDGFP annual survey for Lake Enemy Swim.

The sport fishery for Pumpkinseeds in Lake Enemy Swim is limited due to their population abundance and small size structure. It currently takes an estimated 10.7 years for a Lake Enemy Swim Pumpkinseed to reach 200 mm (i.e. preferred length). With an estimated maximum age of 11.1 years, few fish reach 200 mm before succumbing to mortality. In 2003, the size structure was high, the PSD was 73 and PSD-P was 9 (Weimer and Brown 2006), indicating fish ≥ 200 mm were present but not abundant. Since the early 2000s, the size structure has declined, with 2015 being the last year a preferred-length fish was sampled. Angler harvest may contribute to few fish exceeding 200 mm. The length of angler-harvested Bluegills from Lake Enemy Swim during the 2005 and 2006 summers ranged from 140–280 mm and averaged 200 mm (Blackwell et al. 2007).

The high abundance of Bluegills in Lake Enemy Swim (SDGFP 2024) may negatively influence the Pumpkinseed population abundance. Osenberg et al. (1988) suggested that competition between juvenile Pumpkinseeds and Bluegills is driven by the effects of adult food resources on the adult performance and the eventual recruitment of juveniles. Where zooplankton production is high, adult Bluegills experience increased growth and reproduction, which can lead to more Bluegill larvae, and subsequent competition for food resources among juvenile Bluegills and Pumpkinseeds. Pumpkinseed densities in two Michigan lakes having Bluegills were significantly lower than in a neighboring lake without Bluegills (Osenberg et al. 1992). In the lake without Bluegills, juvenile Pumpkinseed growth was good, and the abundance of juveniles and adults was high, but adult growth was poor because snail abundance was low (Osenberg et al. 1992). In Ontario, Pumpkinseed populations co-occurring with Bluegills were found to mature later and at a larger size, and the Pumpkinseed females had a lower reproductive investment than populations living without Bluegills (Fox 1994), likely because of the two-stage life history (Osenberg et al. 1992). However, Fox (1994) also indicated that the presence of piscivores such as Northern Pike and Largemouth Bass could increase Pumpkinseed mortality or could lead to decreased juvenile Pumpkinseed growth by confining juveniles to littoral areas where competition with juvenile Bluegills would potentially be high. Lake Enemy Swim has an abundance of piscivores, including Largemouth Bass, Northern Pike, Smallmouth Bass, and Walleye.

Mollusks are considered an important diet item of Pumpkinseed over their geographical distribution (Keast 1978). Zebra Mussels were discovered in Lake Enemy Swim in 2022. The recent infestation of Zebra Mussels may provide a new food source for Pumpkinseeds. Following the invasion of Zebra Mussels into three Canadian waters, Pumpkinseeds were found to consume large quantities of Zebra Mussels during the spring and summer (Colborne et al. 2015). Zebra Mussels represented 57%–82% of the diet across the three populations and were present in the stomachs of 81% of the collected Pumpkinseeds. Before Zebra Mussels were present, gastropods and other benthic invertebrates comprised the Pumpkinseed diets. If Zebra Mussels become a large component of the Pumpkinseed diet in Lake Enemy Swim, their growth may improve.

In addition to providing a new food source and potentially improving Pumpkinseed growth, changes to available habitat and the fish community are likely to occur following the introduction of Zebra Mussels. These changes could also impact Pumpkinseed population dynamics. In Oneida Lake, New York, Pumpkinseed abundance increased once Zebra Mussels were present (Irwin et al. 2016). It is anticipated that because of the filtering of water by Zebra Mussels, water clarity will increase, the abundance of submerged aquatic vegetation will subsequently increase, and trophic interactions will be disrupted. The clear water and increase in submerged vegetation will likely change predator-prey dynamics. Information concerning changes to fish communities following the introduction of Zebra Mussels has been ambiguous, necessitating long-term data collection before and after invasions to monitor changes that may occur.

Summary

The Lake Enemy Swim Pumpkinseed population in 2023 was at a low abundance level, and relative abundance has declined over the past 25 years. Growth was average, the population size structure has decreased over time, and body condition (i.e. Wr) has remained relatively high. Recruitment was stable in recent years but has been at a low magnitude. The sport fishery for Pumpkinseeds is limited due to the low population abundance and low size structure (i.e. few fish ≥ 200 mm). Lake Enemy Swim provides habitat conditions necessary to support a Pumpkinseed population and has the most consistent Pumpkinseed population in South Dakota. Our study provides baseline information for evaluating potential population changes that may result following the introduction of Zebra Mussels. We encourage collecting fish population data and habitat information before and after invasions of Zebra Mussels or other invasive species to document their impacts on fish populations. The information from this study will benefit future research and management of Pumpkinseed populations.

Authors’ contributions

Jeston D. Hassler: Conception and design, analysis and interpretation of data, drafting of the paper, final approval, and agrees to be accountable for all aspects of the work.

Brian G. Blackwell: Conception and design, analysis and interpretation of data, drafting of the paper, revising it critically for intellectual content, final approval, and agrees to be accountable for all aspects of the work.

Todd M. Kaufman: Conception and design, revising it critically for intellectual content, final approval, and agrees to be accountable for all aspects of the work.

Acknowledgements

We are grateful to the South Dakota Department of Game, Fish and Parks (SDGFP) employees who helped to collect Pumpkinseeds in 2023 and the many SDGFP personnel who assisted with the Lake Enemy Swim annual fish community survey from 1999-2023. We are also thankful to Alison Coulter, Hannah Mulligan, and two anonymous reviewers for improving the manuscript through their reviews.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

Data supporting the findings of this study are available from the corresponding author [BGB] upon reasonable request.

Additional information

Funding

This project was funded in part by a South Dakota Federal Aid in Sport Fish Restoration grant, F-21-R, activity 2102.