Data from: Large fish eggs may lose their edge as temperature rises
Abstract
It is a nearly universal truth that larger fish eggs have increased chances of survival. However, theory predicts that as temperatures rise, larger eggs may suffer the costs of oxygen limitation and lose their advantage altering the optimal life history trade-off between fecundity and offspring size. Whether these effects may happen under the predicted warming of climate change scenarios is still unknown. Here we show that wild Esox lucius females lay smaller eggs later in the season when temperatures are higher and that this was associated with a seasonal decline in female body size. Experimentally, we found that larger eggs had higher survival rates at lower temperatures, but this advantage diminished in rising temperatures and disappeared entirely in temperatures (~18ºC) that could arise under climate change. The results demonstrate that the optimal egg size is temperature-dependent, and that future warming may favor smaller females with smaller, more numerous eggs, which may profoundly affect population dynamics and the evolutionary optima of life-history traits.
https://doi.org/10.5061/dryad.brv15dvkh
Description of the data and file structure
All data files are stored in the folder Data.zip which includes an internal folder structure to separate files from different sources: data from experiment, data from temperature loggers used at the field site, and data from temperature loggers used to monitor temperatures in the experimental treatments in the lab. The description below details the contents for each file, including its location in the Data.zip.
Files and variables
Data from temperature loggers deployed in the field to monitor the temperature range during spawning
Data/Temp_loggers_field/2021/Lervik1.csv
Data/Temp_loggers_field/2021/Lervik2.csv
Data/Temp_loggers_field/2022/10664550.csv
Data/Temp_loggers_field/2022/10603464.csv
Data/Temp_loggers_field/2023/HOBO_10664550_Lervik_wetland_2023_total.csv
Data/Temp_loggers_field/2023/HOBO_10664557_Lervik_wetland_2023_total.csv
Data/Temp_loggers_field/2024/Lervik_start20241503_rep1.csv
Data/Temp_loggers_field/2024/Lervik_start20241503_rep2.csv
Data files in the format .csv using delimiter ";". Files originate from HOBO Onset temperature loggers that recorded ambient water temperature during the spawning seasons 2021 - 2024. Two loggers were used per year. Data points that fall outside the study period (see script or manuscript) are necessarily from the study area and should not be used.
All files from the temperature loggers contain temperature data with timestamps, but the variable names can differ slightly between files. Below are two examples. The script loads all samples, harmonizes the column names, and merges the data frames together before use.
Variables in file:
# = row number
Date Time, GMT+01:00 = timestamp in the format YYYY-MM-DD HH:MM
Temp, °C (LGR S/N: 10664550 SEN S/N: 10664550 LBL: Temp) = temperature measurements in degrees Celsius with 3 decimals.
Coupler Detached (LGR S/N: 10664550) = information about docking station detachment ("logged"). This variable is not used.
Coupler Attached (LGR S/N: 10664550) = information about docking station connection ("logged"). This variable is not used.
Host Connected (LGR S/N: 10664550) = information about logger stopped. This variable is not used.
End Of File (LGR S/N: 10664550) = information stating end of file. This variable is not used.
(NOTE! The 8-digit identification number for the logger is incorporated in the column names for all columns except datetime and row numbers(#). This thus means that the column names vary between loggers' files, but only one example is given here above.)
Data from temperature loggers deployed in the lab to monitor temperature in experimental treatments
Data/Temp_loggers_lab/2013443_18C_2.csv
Data/Temp_loggers_lab/10664560_10C_1.csv
Data/Temp_loggers_lab/10664564_14C_2.csv
Data/Temp_loggers_lab/10664568_6C_1.csv
Data/Temp_loggers_lab/20160553_18C_1.csv
Data/Temp_loggers_lab/20160554_14C_1.csv
Data/Temp_loggers_lab/20160555_10C_2.csv
Data/Temp_loggers_lab/20160564_6C_2.csv
Datafiles in the format .csv using delimiter ",". Files originate from eight HOBO Onset temperature loggers that recorded ambient water temperature in the mesocosm rooms used for the laboratory treatments in the experiment. There were two replicate loggers per treatment/room. The end of the filenames include information of which treatment (mesocosm room) that logger was deployed in.
Variables in file:
# = row number
Date Time, GMT+01:00 = timestamp in the format DD/MM/YY HH:MM:SS fm/em
Temp, °C (LGR S/N: 20160555, SEN S/N: 20160555, LBL: Temp) = temperature measurements in degrees Celsius with 3 decimals
Coupler Detached (LGR S/N: 20160555) = information about docking station detachment ("logged"). This variable is not used.
Host Connected (LGR S/N: 20160555) = information about host connection ("logged"). This variable is not used.
Coupler Attached (LGR S/N: 20160555) = information about docking station connection ("logged"). This variable is not used.
Stopped (LGR S/N: 20160555) = information about logger stopped. This variable is not used.
End Of File (LGR S/N: 20160555) = information stating end of file. This variable is not used.
(NOTE! The 8-digit identification number for the logger (labeled "S/N:") is incorporated in the column names for all columns except datetime and row numbers (#). This thus mean that the column names vary between loggers files, but only one example is given here above.)
Egg size data from field study over four years (2021-2024) used to assess if egg size is affected by reproductive timing (arrival to spawning grounds)
Data/Field study_egg size variation across years_data.csv
The data file is in .csv format, using a comma (",") as the delimiter. It originates from a field study and contains data on the egg dry mass of females arriving at the spawning area over four spawning seasons for the anadromous population in Lervik (sampling location: 57.07298, 16.521882). Each individual was tagged with Passive Integrated Transponders (PIT-tags) for identification upon recapture. A subsample of eggs from each individual and recapture was dried at 50°C. The number of eggs was counted from photos taken of the subsample before drying. Standard length was measured from photos taken of each individual upon each capture.
Variables in file:
Date = Date in the format YYYY-MM-DD
PIT_ID= Unique identifier for each individual
Mass (g)= Total dry mass of the egg sample
Nr of eggs= Number of eggs in the sample
Standard_length= Standard length measured in centimeters
**Egg size metrics: dry mass vs. volume data set **
The data file includes data from a subset of samples where both egg dry mass and volume were estimated for each sample, enabling an assessment of the correlation between these two metrics.
Data/Field study_egg volume to mass relationship_data.csv
Note: One missing value in the Nr_egg_hydrated column is represented by an empty cell.
Variables in file:
Date = Sampling date in day-month format (DD-mon)
PIT_ID = Unique identifier for each individual
Mass (g) = Total dry mass of the egg sample
Nr of eggs = Number of eggs in the sample
Nr_egg_hydrated = Number of hydrated eggs in 1 ml sample (volume measurement)
Egg size influence on thermal performance in offspring: lab results
Data/Lab_exp_offspring survival_data.csv
The data file is in .csv format, using a comma (",") as the delimiter. It contains data from an experimental lab study on the survival of eggs under four different temperature treatments (A=6°C; B=10°C; C=14°C; D=18°C), involving 75 different females. Each female and treatment has two replicates. The file also includes metadata about the females, such as egg dry mass, total length, and the date of arrival at the spawning ground (which is the same as the date when the female was included in the experiment).
Variables in file (unit in parentheses):
Start_date = Date when sample was taken, which also corresponds to the arrival of the female to the spawning ground, format = YYYYMMDD.
Replicate_ID =Unique identifier for each technical replicate, coded as treatment letter + female number + ":" + replicate number (e.g. A28:1).
Treatment = Temperature treatment: A=6°C, B=10°C, C=14°C, D=18°C.
Female = Unique identity for each female used in the lab
Replicate = Number for each of the two technical replicates (1 or 2) for each treatment and individual
Temp = (°C) Temperature for each temperature treatment
Start_nr_eggs = Number of eggs in each replicate at start of the experiment. Forms the starting point of the experiment.
Nr_viable_larvae = Number of larvae alive at end of yolk-sac absorption. Forms the endpoint of the experiment.
Termination_date = Date of termination for each replicate. Format YYYYMMDD.
PIT_ID = Unique identifier for each individual.
Egg_nr = (count) Total number of eggs in the sample used for dry mass estimate.
Mass_gr = Total dry mass of the egg sample used for dry mass estimate (g).
Length= Total length of female (cm).
Standard_length= Standard length measured in centimeters.
Data/Lab_exp_oxygen_data.csv
The data file is in .csv format, using a comma (",") as the delimiter. It contains the oxygen measurements taken in the experimental treatments during the laboratory study. Oxygen levels were monitored throughout the experiment by daily measurements in three random replicates of each temperature treatment.
Variables in file (unit in parentheses):
Date = Date of the measurement, format YYYYMMDD.
Temp = Temperature treatment in which the measurement was taken, in degrees Celsius (°C); values 6, 10, 14 and 18, corresponding to treatments A, B, C and D.
Replicate = Identifier of the replicate in which the measurement was taken.
Oxygen = Dissolved oxygen concentration measured in the replicate (mg/l).
Missing values
Missing values in this dataset mean "not available": the information could not be obtained for that record. No missing values were infilled, estimated or imputed.
- In Data/Field study_egg volume to mass relationship_data.csv, one missing value in the
Nr_egg_hydratedcolumn is represented by an empty cell. - In all other files, missing values are coded as
NA.
Code/software
All analyses were performed using R version 4.4.1 (2024-06-14 ucrt). The R scripts included (in the linked Zenodo deposit) are split up on three files, see list below for short descriptions of the content in each file. All three scripts are in markdown format (.Rmd) and the scripts are annotated to describe and explain the workflow. The three scripts perform independent tasks and are not dependent on each other.
Session information:
Platform: x86_64-w64-mingw32/x64
Running under: Windows 11 x64 (build 22631)
Matrix products: default
Locale:
-
LC_COLLATE=Swedish_Sweden.utf8
-
LC_CTYPE=Swedish_Sweden.utf8
-
LC_MONETARY=Swedish_Sweden.utf8
-
LC_NUMERIC=C
-
LC_TIME=Swedish_Sweden.utf8
Time zone: Europe/Stockholm
tzcode source: internal
attached base packages:
- stats
- graphics
- grDevices
- utils
- datasets
- methods
- base
Additional packages were loaded automatically as dependencies; the full set can be reproduced by running sessionInfo()
TEMPTRACK_survival experiment_analysis_R.Rmd
This script loads the survival data from the lab and performs statistical analyses and produces figures 2, 3 and 4. It also extracts descriptive statistics about the raw data, the females included in the lab, temperature in the field (from HOBO loggers), temperature in laboratory treatments, and measured oxygen levels in the treatment.
R packages used:
- car (3.1-3)
- carData (3.0-5)
- devEMF (4.5)
- DHARMa (0.4.6)
- dplyr (1.1.4)
- emmeans (1.10.5)
- forcats (1.0.0)
- ggeffects (1.7.1)
- ggplot2 (3.5.1)
- ggpubr (0.6.0)
- glmmTMB (1.1.10)
- knitr (1.48)
- lmtest (0.9-40)
- lubridate (1.9.3)
- modelsummary (2.2.0)
- purrr (1.0.2)
- rcompanion (2.4.36)
- readr (2.1.5)
- scales (1.3.0)
- sjPlot (2.8.16)
- slider (0.3.2)
- stringr (1.5.1)
- tibble (3.2.1)
- tidyr (1.3.1)
- tidyverse (2.0.0)
- zoo (1.8-12)
TEMPTRACK_egg size field study_analysis_R.Rmd
This script loads the egg size data from four consecutive years (2021-2024) and analyses the effect of reproductive timing (Julian date for arrival of the female to the spawning area) on egg size. It also evaluates the effect of size (standard length) on egg size for the females in the field dataset.
R packages used:
- devEMF (4.5)
- DHARMa (0.4.6)
- dplyr (1.1.4)
- forcats (1.0.0)
- ggplot2 (3.5.1)
- ggpubr (0.6.0)
- glmmTMB (1.1.10)
- knitr (1.48)
- lubridate (1.9.3)
- mediation (4.5.1)
- purrr (1.0.2)
- readr (2.1.5)
- sjPlot (2.8.16)
- stringr (1.5.1)
- tibble (3.2.1)
- tidyr (1.3.1)
- tidyverse (2.0.0)
TEMPTRACK_volume_vs_mass_analysis_R_2.Rmd
This script egg size data from a data subset where egg size was both by dry mass and volume, to test for a correlation between the two metrics.
R packages used:
- dplyr (1.1.4)
- forcats (1.0.0)
- ggplot2 (3.5.1)
- lubridate (1.9.3)
- purrr (1.0.2)
- readr (2.1.5)
- stringr (1.5.1)
- tibble (3.2.1)
- tidyr (1.3.1)
- tidyverse (2.0.0)
This study was conducted with pike from an anadromous population that migrates from the Baltic Sea to reproduce in a small creek and adjacent wetland near Lervik, southern Sweden (57.071615, 16.527546). A four year study was conducted to assess egg size variation over the spawning season that extends from March to May, and at temperatures from 4 - 21°C. The field study was combined with a split-brood experiment to evaluate how egg size influences temperature-dependent survival (see below). Ovulating females (Ntot = 262) were captured during the reproductive seasons of 2021-2024 using a stream-wide fyke net. Following capture, each female was dry stripped of approximately 20 ml of eggs that were placed on ice, to standardize conditions prior to determining egg size and performing artificial fertilizations, until reaching the laboratory facility. Females were tagged with Passive Integrated Transponders (HDX23, Biomark, Boise, Idaho, USA) prior to release, to enable individual identification upon recapture. Each individual was photographed on the left side while positioned flat alongside a reference scale to enable standardized measurements of standard lengths. These measurements were obtained by digitizing landmarks using the software TpsDig (version 2.31) and extracting the data with R. To determine egg size, a 1 ml subsample of eggs from each female was spread in a Petri dish, photographed, and then dried at 60°C overnight before being weighed. Egg size was calculated by dividing the total dry weight of the 1 ml egg sample by the total number of eggs (this is done by the script). Dry weight was used as a proxy for egg size, as it is well-established that these measurements are correlated. This correlation was confirmed in the study based on volume and dry weight measurements for 27 females. Besides egg dry mass, we recorded the date for the egg samples (and thus arrival to the spawning area) and identity of the female (PIT_ID) for each sample.
A split-brood experiment was conducted to evaluate how egg size influences temperature-dependent survival. Eggs from 75 pike families were sampled during the spawning season in 2022 and incubated at four different temperatures (6, 10, 14, and 18 ºC) using a full-factorial nested design with two replicates per family and temperature treatment, resulting in 600 experimental units. The eggs were incubated in temperature-controlled mesocosm rooms, and each replicate was monitored daily. Dead eggs and embryos were recorded and removed, and the number of viable embryos was determined at the end of the experiment. Water exchanges were conducted manually at fixed intervals to mimic oxygen availability changes with temperature, ensuring that oxygen depletion did not occur. The data from the experiment was used to evaluate how temperature variation affects egg size-dependent survival. Oxygen levels in the treatment were monitored throughout the experiment by daily measurements in three random replicates of each treatment. Temperature was measured with two HOBO Onset temperature loggers in each treatment. Similarly, two HOBO Onset temperature loggers were deployed in the spawning area to monitor the natural temperature regime during spawning season.