DOI: 10.5061/dryad.fj6q5742c
title: The wash zone and habitat use among three benthic fish species in stratified lakes

description: 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.
description: 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.
description: # 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
 KSK_MNT_temp_data.csv 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. KSK_MNT_catch_data.csv 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