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The wash zone and habitat use among three benthic fish species in stratified lakes

Cite this dataset

Bell, Allan; Middel, Trevor; Ridgway, Mark (2024). The wash zone and habitat use among three benthic fish species in stratified lakes [Dataset]. Dryad.


Mixing processes in lakes are important in determining sedimentation zones and in setting the so-called “wash zone”, the area of lake bottom in contact with an oscillating thermocline during wind driven internal seiche events. The wash zone also aligns with a sharp change in sediment roughness and hardness. Taken together these rapid changes in temperature and sediment indicate that the wash zone is a distinctive ecotone in stratified lakes.  Depth stratified randomized netting was used to develop count-based habitat use models for three common benthic fish species as a function of depth or temperature covariates.  Using data from two lakes with quite different wash zone depths, we show the wash zone to describe fish habitat for two of three benthic fish species by utilizing the top 50% of estimated fish abundance as an indicator of habitat use. White sucker (Catostomus commersoni) habitat use was fully within the boundaries of the wash zone. Lake whitefish (Coregonus clupeaformis) habitat was adjacent and within the wash zone. Longnose sucker (C. catostomus) habitat use was in the deep areas of lakes dominated by sediment focusing and did not overlap white sucker. Lake whitefish habitat use overlapped both catostomids, but peak abundance of both lake whitefish and white sucker overlapped pointing to potential interactions between these species. Smaller lakes have less vigorous mixing processes and a narrower wash zone, so with a decline in lake size the likely area of the wash zone as habitat for benthic feeding fish would become smaller.

README: The wash zone and habitat use among three benthic fish species in stratified lakes

The data and code in this Dryad support the re-creation of the analysis in the referenced manuscript. The manuscript contains analysis standardized single-pass benthic gill-netting surveys. Two hour duration benthic gill-nets were used in depth stratified, randomized surveys conducted in two large lakes in Algonquin Provincial Park using standard Summer Profundal Index Netting (SPIN) gillnets. Surveys were conducted during periods of thermal stratification (July-August) in the daytime. Each site was sampled once during a survey.

Temperature and DO profiles were collected mid-basin in each lake during the netting surveys.

Description of the data and file structure

Analysis code is provided as .R scripts and is commented. Depth and temperature rasters for mapped analysis are in .Rdata format whereas all other data is in .csv format. .R files can be opened in any R editor, but are best viewed in RStudio. .Rdata files can be opened in any instance of R.

Figure 1

Figure_1_code.R - R code to regenerate Figure 1 in manuscript
KSK_MNT_temp_data.csv - temperature data at 1 metre depth intervals for both lakes.

Habitat and abundance analysis:

Lake_whitefish.R - R code to regenerate Lake Whitefish analysis results including Figure 2 and habitat raster in Figure 4.
White_sucker.R - R code to regenerate White Sucker analysis results including Figure 2 and habitat raster in Figure 5.
Longnose_sucker.R - R code to regenerate Longnose Sucker analysis results including Figure 2 and habitat raster in Figure 6.
KSK_MNT_catch_data.csv - catches of three species at each netting site including coordinates, depth, and temperature.
Depth_raster.Rdata - raster file of lake depth for both lakes at 64X64 meter resolution.
Temp_raster.Rdata - raster file of lake temperature for both lakes at 64X64 meter resolution.

Figure 3

Figure_3_code.R - R code to regenerate Figure 3 in manuscript. Data to generate plot is within R code.

Data Definitions for CSV files

Source: Data are derived from temperature at depth data collected by Harkness Lab suring netting survey period

PRJ_CD - Unique code for netting surveys on each lake
Location - Identification code if more than one profile is taken
Lake - Lake name
Depth - Depth of temperature measurement in metres.
Temp - Water temperature at depth in degrees celsius.

Source: Data are derived from netting and environmental data collection conducted by Harkness Lab.
Lake - Lake Name
Site - Netting site number
P1_LW_Count - Count of Lake Whitefish caught
P1_LW_PA - Presence/absence of Lake Whitefish
P1_LS_Count - Count of Longnose Sucker caught
P1_LS_PA - Presence/absence of Longnose Sucker
P1_WS_Count - Count of White Sucker caught
P1_WS_PA - Presence/absence of White Sucker
X - UTM 17N Easting coordinate of site
Y - UTM 17N Northing coordinate of site
AVG_Depth - Average depth of site units=meters
AVG_Temp - Average temperature of site units=degree celsius
lakeid - ID column for lake parameter in model


The study focused on Lakes Manitou (46.015; -78.992) and Kioshkokwi (46.078; -78.885) in the northwest corner of Algonquin Park, Ontario, Canada (see Fig. S1 in Supplement). Both are large oligotrophic lakes (Manitou, secchi depth = 2.75 m, TP = 6.6 μg/L; Kioshkokwi, secchi depth = 3.7 m, TP = 7.5 μg/L) with similar morphometries (Manitou, SA = 1,382 ha, max. depth = 38.4 m,  depth = 13.6m; Kioshkokwi, SA = 1,070 ha, max. depth = 47.4 m, depth = 13.9 m). Manitou drains to Kioshkokwi.

We evaluate habitat use hypotheses based on mapping of habitat use models stemming from catch data following depth-stratified randomized netting (2 hour soak time per net) in each lake. The netting details are as follows: 

Gill nets were 64x2 m in total length and height, respectively, composed of 8 single mesh panels (8 m each) sewn together. The mesh series included 2.25 inches (57mm), 2.5” (64mm), 2.75” (70mm), 3.0” (76mm), 3.5” (89mm), 4.0” (102mm), 4.5” (114mm), and 5.0” (127mm) stretch mesh with monofilament diameter for each mesh being 0.23, 0.23, 0.23, 0.28, 0.28, 0.33, 0.33, and 0.33 mm, respectively.

Net sites were depth stratified and randomly allocated within strata proportional to stratum surface area. Depth strata were 2-10 m, 10-20, 20-30, 30-40 and 40-60 m. The total number of net sets (N=65 for Kioskokwi; N=78 for Manitou) was determined by the formula: total net sets = 0.0184*(lake surface area) + 24.  Nets were set for 2 hours during the day (08:00-16:00), and net sites were sampled once in each survey. Lake surveys were conducted in the summer of 2015 (Lake Kioshkokwi July 21-23; Lake Manitou Aug 11-13).

Habitat use models were based on catch counts for the three species using either count regression or hurdle models incorporating a negative binomial assumption in data distribution.