DOI: 10.5061/dryad.x69p8czr4
title: Data from: Thermal habitat fragmentation in stratified lakes induces resource waves that brook charr track across seasons

description: The spatial configuration of thermal habitats constrains the
 thermoregulatory performance of ectotherms. Thermal landscapes also vary
 through time, which is particularly relevant in seasonal environments such
 as temperate lakes. Indeed, elevated temperatures in the epilimnion of
 dimictic lakes during summer could substantially reduce the use of this
 habitat by cold-stenothermic fish during the stratified period. The main
 objective of this study was to evaluate whether thermal habitat
 fragmentation in stratified lakes modulates accessibility to resources
 that brook charr, Salvelinus fontinalis, which is a mobile consumer, can
 track across seasons. More specifically, we hypothesize that reduced
 access to the littoral habitat during summer enhances foraging
 opportunities in this habitat during winter. We used an automatic acoustic
 telemetry system offering full coverage of the lake to continuously record
 brook charr locations across seasons, and we estimated zoobenthos
 abundances in the littoral habitat using image processing and
 semi-automatic classification. While brook charr concentrate in the
 metalimnion of the pelagic habitat in summer, most individuals in winter
 shift to a shallow bay that is unexploited in summer due to thermal
 constraints. In this habitat, zoobenthos abundance is more than twice as
 high at the end of the summer compared to littoral habitats close to the
 thermal refuge in the pelagic habitat. Surprisingly, brook charr showed
 strong within-lake site fidelity between two consecutive summers, which
 suggests that spatial memory could be a key driver of seasonal habitat use
 in this lacustrine population. Overall, our results suggest that thermal
 barriers create fragmentation between littoral and pelagic habitats that
 in turn produces resource opportunities that brook charr can track across
 seasons.
description: The study was carried out in Lake Ledoux (46° 38’ N, 73° 15’ W),
 Mastigouche Wildlife Reserve, Québec, Canada, from 2016 to 2018. Lake
 Ledoux is a typical small oligotrophic temperate zone lake with respect to
 surface area (11.9 ha), mean depth (5.5 m), maximum depth (18.0 m), and
 general physicochemical characteristics (Gignac-Brassard et al. 2023,
 Magnan 1988). Brook charr is the only fish species in the lake, and sport
 fishing is rigorously controlled by the Québec Government (Bourke et al.
 1996). The lake was closed to fishing during the three years of the study,
 but illegal fishing was observed in Lake Ledoux (M. Pépino, personal
 observation; see details in Supplement 1). We deployed
 acoustic telemetry positioning arrays to continuously follow brook charr
 movements and habitat use at fine spatiotemporal scales (&lt;1 min,
 &lt;5 m resolution) using two different VEMCO Positioning Systems
 (VPS). From 5 to 7 July 2016, we deployed 10 receivers
 (VR2Tx-069k-111-BAT; VEMCO Inc., Halifax, NS, Canada) and two reference
 tags (V9TP-2x-069k-1-0034m; VEMCO Inc.). From 7 to 8 November 2016, four
 additional receivers were deployed to allow better coverage of the study
 lake during winter, especially in the shallow bay in the western section
 of the lake (Fig. 1; Supplement 1). This VR2 positioning system was
 operational from 7 July 2016 until 22 May 2017, but full coverage of the
 lake was not accomplished until we added the four additional receivers in
 November 2016. Furthermore, the first VPS analyses revealed potential
 “collisions” between tag signals, which occur when individuals are in
 proximity and create interference during signal transmission. In 2017, we
 changed to the HR2 VPS technology, which was specifically developed to
 circumvent this problem. This system consisted of 23 receivers
 (HR2-180k-100; VEMCO Inc.) and four reference tags (V9TP-2x-180k-34m;
 VEMCO Inc.). This HR2 VPS was operational from 21 June 2017 until 6
 November 2018 and provided full coverage of the lake. Details of the VR2
 and HR2 VPS as well as VPS performance are provided in Supplement
 1.
description: # Thermal habitat fragmentation in stratified lakes induces resource waves
 that brook charr track across seasons
 [https://doi.org/10.5061/dryad.x69p8czr4](https://doi.org/10.5061/dryad.x69p8czr4) --- We have submitted lake temperature profile data (**Water_Temperature_Data.csv**), benthos count data (**Benthos_Count_Data.csv**), brook charr position data from the VR2 (**FishVUE.csv**) or HR2 (**FishHRtot.csv**) positioning systems, and GIS lake data for lake contour (**ledoux_line.shp**), lake bathymetry (**ledoux_bathy.shp** or **ledoux_raster.tif**) or benthos stations (**ledoux_benthos.shp**) in a .zip file (**Lake_Data.zip**). ## Descriptions ### **Water\_Temperature\_Data** * *Temp*: Temperature (°C) * *Depth*: Depth (m) * *DateUTC*: Time in universal time zone (yyyy-mm-dd hh:mm:ss) * *DateEDT*: Time in Eastern/Canada time zone (yyyy-mm-dd hh:mm:ss) * *Set*: Interger from the first (1) to the last (5) download of the temperature data * *Day*: Date (yyyy-mm-dd) ### **Benthos\_Count\_Data** * *Month*: Integer corresponding to the month of the year (**6**: June ; **9**: September) * *Station*: Station number (interger) * *Group*: Taxonomic group (*Anisoptera*, *Chironomidae*, *Ephemeroptera*, *Gammaridae*, *Trichoptera*, or *Zygoptera*) * *Accessibility*: Station classified as accessible (**Yes**) or inaccessible (**No**) to brook charr * *Count*: Zoobenthos abundance (integer) ### **FishVUE** Brook charr positions from the VR2 positioning system * *X*: x-coordinate in UTM zone 18N (EPSG: 32618) * *Y*: y-coordinate in UTM zone 18N (EPSG: 32618) * *TRANSMITTER*: Fish specimen ID * *DATETIME*: Time in universal time zone (yyyy-mm-dd hh:mm:ss) * *LAT*: Latitude (decimal degree) * *LONG*: Longitude (decimal degree) * *HPE*: Horizontal positionning error. HPE is a measure of the error potential of a calculated position due to the effects of the geometry of the positions of the transmitter and the detecting receivers (unitless) * *TEMP*: Temperature recorded by the sensor (°C) * *DEPTH*: Depth recorded by the sensor (m) * *Season*: One of the two following seasons: **Summer 2016** or **Winter 2017** ### **FishHRtot** Brook charr positions from the HR2 positioning system * *X*: x-coordinate in UTM zone 18N (EPSG: 32618) * *Y*: y-coordinate in UTM zone 18N (EPSG: 32618) * *Name*: Fish specimen ID * *Time*: Time in universal time zone (yyyy-mm-dd hh:mm:ss) * *Longitude*: Longitude (decimal degree) * *Latitude*: Latitude (decimal degree) * *HPE*: Horizontal positionning error. HPE is a measure of the error potential of a calculated position due to the effects of the geometry of the positions of the transmitter and the detecting receivers (unitless) * *RMSE*: Root-mean-squared error. RMSE is a measure of detection time error for a given position. The primary use for the RMSE is to indicate potential positioning error due to multipath signals (milliseconds) * *TempData*: Temperature recorded by the sensor (°C) * *DepthData*: Depth recorded by the sensor (m) * *Season*: One of the three following seasons: **Summer 2017**, **Winter 2018**, or **Summer 2018** ### **Lake\_Data** .zip file containing raster of shapfile data as described below: * *ledoux_bathy.shp*: shapefile for lake bathymetry (linestring; projected CRS: WGS 84 / UTM zone 18N). The attribute table contains the following variables: * *ID*: Element ID * *CONTOUR*: altitude above the sea level of the lake depth (m) * *Surface*: altitude above the sea level of the lake surface (m) * *Bathy*: Lake depth (m) * *ledoux_benthos.shp*: shapefile for benthos stations (point; projected CRS: WGS 84 / UTM zone 18N). The attribute table contains the following variables: * *Latitude*: Latitude (decimal degree) * *Longitude*: Longitude (decimal degree) * *y_proj*: y-coordinate in UTM zone 18N (EPSG: 32618) * *x_proj*: x-coordinate in UTM zone 18N (EPSG: 32618) * *time*: Time in universal time zone (yyyy-mm-dd hh:mm:ss) * *model*: GPS model * *ltime*: Time in Eastern/Canada time zone (yyyy-mm-dd hh:mm:ss) * *Station*: Station number * *ledoux_line.shp*: shapefile for lake contour (linestring; projected CRS: WGS 84 / UTM zone 18N). The attribute table contains the following variables: * *Id*: Element ID * *CONTOUR*: altitude above the sea level of the lake shoreline (m) * *ledoux_raster.tif*: raster data for lake bathymetry (crs: +proj=utm +zone=18 +datum=WGS84 +units=m +no_defs). Values refer to lake depth (m). * *Dimension*: 395, 1254, 1 (nrow, ncol, nlyr) * *Resolution (m)*: 1, 1 (x,y) * *Extent*: 630707.4, 631961.4, 5184475, 5184870 (xmin, xmax, ymin, ymax) * *Min value*: 0 * *Max value*: 17 ### **R code for reading files** These above files can be easily uploaded in the R environment using the following code: ``` #Water_Temperature_Data water_temp &lt;- read.csv('Water_Temperature_Data.csv',sep=";",dec=".",head=TRUE) #Benthos_Count_Data benthos = read.csv('Benthos_Count_Data.csv',sep=";",dec=".",head=TRUE) #FishVUE library(data.table) VUE = fread('FishVUE.csv',sep=",",dec=".",h=TRUE) #FishHRtot library(data.table) HR = fread('FishHRtot.csv',sep=",",dec=".",h=TRUE) #Lake data library(terra) library(sf) lake_bathy &lt;- read_sf('ledoux_bathy.shp') lake_benthos &lt;- read_sf('ledoux_benthos.shp') lake_line &lt;- read_sf('ledoux_line.shp') ledoux_depth &lt;- rast('ledoux_raster.tif') ```