DOI: 10.5061/dryad.kkwh70sjc
title: Data and code from: Effects of temperature and browning on the functional response of a freshwater top predator

description: This dataset contains data and code underlying a study of how temperature
 and water browning affect feeding rates and functional responses of a
 freshwater top predator, the northern pike (Esox lucius). The archive
 includes data from two controlled laboratory experiments quantifying pike
 feeding on roach across gradients of temperature, prey density, and water
 colour (browning), as well as year-round body temperature records from
 free-ranging adult pike equipped with implanted biosensors. Experiment 1
 provides replicated functional-response data across three temperatures (5,
 9, and 13 °C) and two visual conditions (clear and brown water) at four
 prey densities. Experiment 2 quantifies feeding rates at two prey
 densities across a browning gradient ranging from completely clear to
 extremely brown water. Additional files include predator body mass
 measurements and continuous body-temperature time series used to validate
 climatic simulations of winter thermal regimes. All raw data, processed
 variables, and fully reproducible R code used for statistical analyses,
 functional-response fitting, model comparison, and figure generation are
 included.
description: Experiment 1: We quantified functional
 responses of pike foraging on roach at three temperatures (5°C, 9°C, and
 13°C) and two levels of visual condition (clear and brown water). We
 performed the foraging trials in the laboratory at four prey densities (2,
 5, 10, or 20 roach per 700L). Foraging trials were performed in six tanks
 with an interior dimension of 121cm x 104 cm (length x width) filled to
 56cm with filtered and aerated water (total water volume: 704L). Visual
 conditions were manipulated by adding 3.5g humic acid (Humintech GmbH,
 Germany) to three tanks. The clear water treatment had an absorbance
 (Abs420/5) of 0.020±0.007, and the brown water treatment 0.097±0.012. Each
 of the 24 treatment combinations was replicated eight times. The trials
 lasted 23.5h with a 15-minute acclimation period. Pike were starved for 4
 days at 9°C between trials to standardize hunger levels and motivation. A
 total of 24 pike were used (mean wet weight 51.8±12.8g (mean ±1SD), n=23,
 range: 34.5g – 79.2g). Pike were used for up to 10 foraging trials
 (average=8). Roach were used as prey (wet weight = 0.91±0.34g (mean ±1SD),
 n=47). Experiment 2: We performed
 foraging trials at two prey densities (5 and 10 roach) and five visual
 levels. As before, visual conditions were modified by adding humic acid.
 The absorbance in the browning treatments was 0.02±0.01, 0.08±0.02,
 0.24±0.04, 0.84±0.10 and 3.06±0.22 (mean Abs420/5 ± 1 SD; 7 weekly
 measurements per treatment). The temperature was kept constant at 9°C.
 Pike were fasted for 12 days between Experiment 1 and 2. Foraging trials
 were performed exactly as in Experiment 1. Body
 temperature: We equipped six adult pike with biosensors
 and recorded their body temperature for 12 months in experimental ponds.
 Pike were captured by electrofishing and transported to three experimental
 ponds (70m x 30m, depth 1.5m) where they were placed in keep nets (3 x 3 x
 1.5 m, 1.5 cm mesh size; Pokorný Sítě, Brloh, Czech republic) for
 acclimation. Pike were surgically implanted with Centi-HRT biosensors
 (Star-Oddi, Garðabær, Iceland) set to record body temperatures at 30
 minute intervals and released into the ponds on November 23, 2021. In
 early October 2022, all pike were recaptured by electrofishing, biosensors
 retrieved, and body temperature data downloaded. All
 experiments were conducted under permission from the Malmö/Lund authority
 for ethics of animal experimentation (Licence
 5.8.18-00783/2022).
description: # Data and code from: Effects of temperature and browning on the
 functional response of a freshwater top predator ## Description of the
 data and file structure ### Files and variables #### File:
 data_experiment1.csv **Description:** Dataset from Experiment 1:
 Functional responses at three temperatures and two browning levels. #####
 Variables  - Orig.order: ID used to identify individual records - Temp:
 water temperature (in degrees Celsius) for the three temperature
 treatments - Watercolor: visual conditions, either Clear (Absorbance at
 420nm = 0.02) or Brown (Absorbance at 420nm = 0.097) water - Nprey: the
 number of roach added at the beginning of each 24h trial - Rep: Replicate
 number (1-8) - Pit: individual Pit tag ID for each individual pike
 (predator) - Time.introd: Day and time when the tr pike was introduced to
 the arena - Time.started: Day and time when the trial ended - Time.ended:
 Day and time when the trial ended - Day.all: the time (in Days since the
 experiment started), used as a proxy for habituation - Day.ind: the number
 of days since the first time an individual pike was used in a foraging
 essay - Trial.N: the sequential number of trials an individual has
 experienced at the start of a new trial - Dec.h: duration (in decimal
 hours) of each trial - Nsurv: the number of prey remaining at the end of
 each trial - Eaten: the number of prey eaten during the trial - Outlier:
 identifies three individuals that were excluded from the analysis, as the
 data indicate that they had not started eating in the laboratory during
 the trial #### File: data_experiment2.csv **Description:** Data from
 experiment 2: Feeding rates at two prey densities and five browning
 levels. ##### Variables * Date_started: the day when the foraging trial
 was initiated * Day: the time in days since the experiment started * Temp:
 the water temperature (in degrees Celsius) * Watercolor: visual
 conditions, ranging from entire clear to extremely brown. The measured
 absorbance levels were 0.02±0.01, 0.08±0.02, 0.24±0.04, 0.84±0.10 and
 3.06±0.22 (mean Abs420/5 +-1SD) * N_prey: the number of roach added at the
 beginning of each 24h trial * Rep: replicate number (1-8) * Pit_tag: the
 individual Pit tag ID for each individual pike * N_survived: the number of
 prey remaining at the end of each trial * Eaten: the number of prey eaten
 during the trial #### File: body_temps.csv **Description:** Field body
 temperatures of free-ranging adult pike collected using implanted
 biosensors. ##### Variables * date: date and time of temperature recording
 * temp: temp recorded in degrees Celsius * ind: pit tag ID of individual
 pike #### File: pike_wt.csv **Description:**  ##### Variables * pit: the
 individual Pit tag ID for each individual pike * wt: wet weight in grams *
 date: date when weight measurements were taken ## Code/software Analysis.R
 contains R code for performing all analyses in the MS. Analyses were
 performed in R 4.4.1 Packages used were: dplyr lme4 frair nlstools sjPlot
 car merTools RColorBrewer ## Access information Other publicly accessible
 locations of the data: * N/A Data was derived from the following sources:
 * N/A