DOI: 10.5061/dryad.8w9ghx3xz
title: Body condition and diet data for gamefish in 15 hardwater lakes of southern Saskatchewan, Canada

description: Mitigating threats of aquatic invasive species in lakes requires holistic
 insights into the biological, physical, and chemical conditions sustaining
 fish communities. This study establishes the ecological baseline
 conditions for three key gamefishes—walleye, northern pike, and yellow
 perch—across 15 hardwater prairie lakes in south-central Saskatchewan,
 Canada, that are threatened by zebra mussel invasion. We employed stomach
 content analysis to evaluate diet composition and ontogenetic nutritional
 shifts in adult fishes and assessed how fish size and environmental
 factors influence body condition. Adult walleye transition from a diet of
 amphipods to fishes as they grow, demonstrating greater dietary
 flexibility compared to perch and pike, which maintain a stable diet of
 chironomids and fish, respectively. While walleye and pike decline in body
 condition with size, perch maintain a consistently high body condition as
 they grow. Lake productivity and alkalinity are important predictors of
 body conditions of adult walleye and perch in hardwater prairie lakes.
 Given the combined threats of zebra mussel invasions, climate change, and
 potential local forage fish scarcity, novel management strategies are
 essential.
description: Fish and water sampling were conducted across 15 hard-water lakes
 in south-central Saskatchewan from May to August 2019 to establish
 baseline ecological conditions. Gamefish species (walleye, northern pike,
 and yellow perch) were measured for length and weight. Stomach content
 analysis quantified prey contributions using the index of relative
 importance (IRI). Multivariate analyses (MANOVA, RDA) assessed diet
 variation between size groups while controlling for lake effects. Multiple
 regression and relative importance analysis examined how total length and
 environmental factors (surface area, depth, alkalinity, chlorophyll-a,
 total phosphorus) influenced fish body condition. Permutation tests and
 adjusted R² confirmed that diet composition varied by size in walleye but
 not for perch or pike, while environmental factors had species-specific
 effects on body condition. Associated scripts and code required to
 replicate all analyses in the manuscript are provided.
description: # Body Condition and Diet Data for Gamefish in 15 Hardwater Lakes of
 Southern Saskatchewan, Canada
 [https://doi.org/10.5061/dryad.8w9ghx3xz](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 (&gt; 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 (&gt; 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 &gt; 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.