https://doi.org/10.5061/dryad.8w9ghx3xz

Files and variables

Input files are comma-delimited CSV files containing environmental (env), body condition indices (bci), and diet data matrices for walleye (wa), northern pike (pi), and yellow perch (pe) across multiple spatial scales. These datasets are essential for understanding diet, feeding dynamics, and trends in the well-being of prairie gamefish. Species abbreviations are consistent across datasets, scripts, and data files. For example, the walleye diet data for two size classes are stored in wa_diet_combined_2_classes.csv.

Note: All analyses were conducted using R version 4.2.0 (2020) and associated packages within this version.

File: all_diet.csv

Description: The file (all.diet.csv) contains diet data for three gamefish species—walleye, northern pike, and yellow perch—grouped by size and sampled across multiple spatial scales. Species codes: wa = walleye, pi = pike, pe = perch. A %IRI value of zero indicates that a prey type was absent from the diet of a given species-size class. 

Variables

• species: Common name of gamefish (Walleye, Pike, Perch)
• species.id: Species identification code (1 = Walleye, 2 = Pike, 3 = Perch)
• size: Size group of gamefish (Small or Large)
• size.id: Size group identification code (1 = Small, 2 = Large)
• Prey.items: Food items found in gamefish stomachs
• IRI: Index of Relative Importance of prey items (%)
• se: Standard error of %IRI, indicates how much the sample mean likely deviates from the population mean
• sd: Standard deviation of %IRI, shows variability in prey importance across samples

File: wa_diet_combined_2_classes.csv

Description: 

This file contains supplementary diet data to investigate diet variation between size groups of walleye (species code: wa). The dataset is stored in the wa_diet_combined_2_classes.csv file and accompanied by the MANOVA_walleye_diet R script for analysis.

Variables

• Lakes: Name of lake (no units)
• Species: Common name of gamefish (i.e., walleye; no units)
• Size category: Size group of gamefish (Small or Large)
• Size.cat: Size group identification code (1 = Small, 2 = Large)
• Amphipods: Amphipods found in gamefish stomachs, expressed as %IRI
• Fish: Fish prey found in gamefish stomachs (%IRI)
• Other invertebrates: Non-amphipod invertebrates found in gamefish stomachs (%IRI)
• Plant matter: Plant material found in gamefish stomachs (%IRI)
• Unidentified: Unidentifiable stomach contents (%IRI)

File: pe_diet_combined_2_classes.csv

Description: 

This file contains supplementary diet data for two size groups of perch (species code: pe) sampled across multiple spatial scales. The dataset is available in the pe_diet_combined_2_classes.csv file and accompanied by MANOVA_perch_diet R script for analysis.

Variables

• Lakes: Name of lake (no units)
• Species: Common name of gamefish (i.e., perch; no units)
• Size category: Size group of gamefish (Small or Large)
• Size.cat: Size group identification code (1 = Small, 2 = Large)
• Amphipods: Amphipods found in gamefish stomachs, expressed as %IRI
• Fish: Fish prey found in gamefish stomachs (%IRI)
• Chironomidae: Chironomids found in gamefish stomachs (%IRI)
• Corixidae: Corixids found in gamefish stomachs (%IRI)
• Other invertebrates: Non-amphipod invertebrates found in gamefish stomachs (%IRI)
• Unidentified: Unidentifiable stomach contents (%IRI)

File: pi_diet_combined_2_classes.csv

Description: 

This file contains supplementary diet data for two size groups of pike (species code: pi), sampled across multiple spatial scales. The dataset is available in the pi_diet_combined_2_classes.csv file and accompanied by the MANOVA_pike_diet R script for analysis.

Variables

• Lakes: Name of lake (no units)
• Species: Common name of gamefish (i.e., pike; no units)
• Size category: Size group of gamefish (Small or Large)
• Size.cat: Size group identification code (1 = Small, 2 = Large)
• Amphipods: Amphipods found in gamefish stomachs, expressed as %IRI
• Fish: Fish prey found in gamefish stomachs (%IRI)
• Plant matter: Plant material found in gamefish stomachs (%IRI)
• Unidentified: Unidentifiable stomach contents (%IRI)
• Other invertebrates: Non-amphipod invertebrates found in gamefish stomachs (%IRI)
• Stones: Hard stones present in gamefish stomachs (%IRI)

File: LMM.wa.bci.csv

Description: This file contains the walleye dataset (total length and body condition index), used for Linear mixed-effects (LME) modeling to examine the impact of fish size on body condition. All necessary packages and codes for the analysis are provided in the LMEM_BCI R script.

Variables

• Year: Year of sampling
• Month: Month of sampling
• Lakes: Name of lake (no units)
• LakeID: Lake identification code
• Species: Common name of gamefish (i.e., walleye; no units)
• Gender: Sex of the fish (male or female)
• FishID: Unique fish identification code
• IDcode: First two initials of the species name followed by a unique number (e.g., WA01 for walleye)
• Total.Length.cm: Length measured from the tip of the snout to the tip of the longer lobe of the tail/caudal fin, in cm
• Total.Length.mm: Total length in mm
• Fork Length.cm: Length measured from the tip of the snout to the end of the middle caudal fin rays, in cm
• Std.Length.cm: Length measured from the tip of the snout to the posterior end of the last vertebra, in cm
• Weight.g: Whole body weight in grams
• Wr: Relative weight of the fish (no units)

File: LMM.pi.bci.csv

Description: This file contains the pike dataset, including total length and body condition index (Wr), used for Linear mixed-effects modeling to examine how body size influences body condition across Prairie lakes. All necessary packages and code for the analysis are provided in the LMEM_BCI R script.

Variables

• Year: Year of sampling
• Month: Month of sampling
• Lakes: Name of lake (no units)
• LakeID: Lake identification code
• Species: Common name of gamefish (i.e., pike; no units)
• Gender: Sex of the fish (male or female)
• FishID: Unique fish identification code
• IDcode: First two initials of the species name followed by a unique number (e.g., PI01 for pike)
• Total.Length.cm: Length measured from the tip of the snout to the tip of the longer lobe of the tail/caudal fin, in cm
• Total.Length.mm: Total length in mm
• Fork Length.cm: Length measured from the tip of the snout to the end of the middle caudal fin rays, in cm
• Std.Length.cm: Length measured from the tip of the snout to the posterior end of the last vertebra, in cm
• Weight.g: Whole body weight in grams
• Wr: Relative weight of the fish (no units)

File: LMM.pe.bci.csv

Description: This file contains the perch dataset, (total length and body condition index), used for Linear mixed-effects modeling to investigate how fish size influences body condition across Prairie lakes. All necessary packages and code for the analysis are provided in the LMEM_BCI R script.

Variables

• Year: Year of sampling
• Month: Month of sampling
• Lakes: Name of lake (no units)
• LakeID: Lake identification code
• Species: Common name of gamefish (i.e., perch; no units)
• Gender: Sex of the fish (male or female)
• FishID: Unique fish identification code
• IDcode: First two initials of the species name followed by a unique number (e.g., PE01 for perch)
• Total.Length.cm: Length measured from the tip of the snout to the tip of the longer lobe of the tail/caudal fin, in cm
• Total.Length.mm: Total length in mm
• Fork Length.cm: Length measured from the tip of the snout to the end of the middle caudal fin rays, in cm
• Std.Length.cm: Length measured from the tip of the snout to the posterior end of the last vertebra, in cm
• Weight.g: Whole body weight in grams
• Wr: Relative weight of the fish (no units)

File: Env_wa_mlm.csv

Description: This file contains environmental variables used to quantify key factors affecting the body condition of small and large walleye through multiple regression and relative importance analysis. The code for large walleye (lines 74–153, Figure 4A in the manuscript) and small walleye (lines 254–329, Supplementary Figure S6) is provided in the rel_imp_ev_regressors R script.

Variables

• Lakes: Name of lake (no units)
• wa_small_bci: Body condition index of small walleye (≤ 40 cm TL)
• wa_large_bci: Body condition index of large walleye (> 40 cm TL)
• Surface_area: Lake surface area (km²)
• Max_depth: Maximum depth of lake where sampling took place (m)
• Alkalinity: Measure of lake water hardness (mg L⁻¹)
• TP: Total phosphorus concentration (μg L⁻¹)
• DO: Dissolved oxygen concentration (mg O₂ L⁻¹, % saturation)
• Secchi: Water clarity measured using a black-and-white Secchi disk (m)
• Chl_a: Algal biomass, measured as chlorophyll a (chl a)

File: Env_pe_mlm.csv

Description: This file contains environmental variables used to quantify key factors influencing the body condition of small and large walleye through multiple regression and relative importance analysis. The code for large perch (lines 159–249, Figure 4B in the manuscript) and small perch (lines 334–387, Supplementary Figure S7) is provided in the rel_imp_ev_regressors R script.

Variables

• Lakes: Name of lake (no units)
• pe_small_bci: Body condition index of small perch (≤ 22.5 cm TL)
• pe_large_bci: Body condition index of large perch (> 22.5 cm TL)
• Surface_area: Lake surface area (km²)
• Max_depth: Maximum depth of lake where sampling took place (m)
• Alkalinity: Measure of lake water hardness (mg L⁻¹)
• TP: Total phosphorus concentration (μg L⁻¹)
• DO: Dissolved oxygen concentration (mg O₂ L⁻¹, % saturation)
• Secchi: Water clarity measured using a black-and-white Secchi disk (m)
• Chl_a: Algal biomass, measured as chlorophyll a (chl a)

File: Env_pi_mlm.csv

Description: This file contains environmental variables used to assess key factors influencing the body condition of pike through multiple regression and relative importance analysis. The code for pike (lines 393–444, Supplementary Figure S8) is provided in the rel_imp_ev_regressors R script.

Variables

• Lakes: Name of lake (no units)
• pi_bci: Body condition index of northern pike (both small ≤ 60 cm TL and large > 60cm size were pooled together)
• Surface_area: Lake surface area (km²)
• Max_depth: Maximum depth of lake where sampling took place (m)
• Alkalinity: Measure of lake water hardness (mg L⁻¹)
• TP: Total phosphorus concentration (μg L⁻¹)
• DO: Dissolved oxygen concentration (mg O₂ L⁻¹, % saturation)
• Secchi: Water clarity measured using a black-and-white Secchi disk (m)
• Chl_a: Algal biomass, measured as chlorophyll a (chl a)

Code/software

This dataset contains the data files and codes required to recreate analyses from Ofosu et al. (2025), "Game Over for Gamefish in Prairie Lakes? "(Department of Biology, University of Regina, unpublished manuscript). Files in this repository require R version 2020 4.2 to generate. Users are provided with the appropriate scripts to do so if they wish. Missing data are coded as NA.

The dataset includes fish length, weight, sex, and body condition index (relative weight, Wr) for walleye, northern pike, and yellow perch sampled from May to August 2019, alongside physicochemical lake variables. Prey data obtained from stomach contents, quantified using the index of relative importance (IRI), facilitate diet analyses. Processed datasets are provided for multivariate analyses.

Adult walleye exhibit greater dietary flexibility, transitioning from amphipods to fish as they grow, while perch and pike maintain stable diets of chironomids and fish, respectively. This adaptability allows gamefish to supplement their diets with invertebrates when fish prey is scarce but also raises concerns about trophic bottlenecks and stunted growth. Linear mixed-effects models indicate that walleye and pike decline in body condition with size, whereas perch maintain consistently high body condition. Multiple regression analyses identified lake productivity and alkalinity as key predictors of adult walleye and perch body conditions in hardwater prairie lakes.