https://doi.org/10.5061/dryad.h9w0vt4rb

You will find here the dataset related to the paper "Food chain without giants: Modelling the trophic impact of bowhead whaling on little auk populations in the Atlantic Arctic".

This dataset contains four main files :

• PCBM_Results_10000rep_2024-05-14.txt : The main output of the model
• sf_surfacewhaleauk_depth : The shapefile of the study area
• coast.txt : A latitude/longitude file to identify coast lines
• Food chain of giants_main script.R : Main script 

Description of main output dataframe (PCBM_Results_10000rep_2024-05-14.txt)

This dataframe contains the modelling output of each of the 10,000 Monte-Carlo repetitions. Titles are in French, with the following translation for abbreviations :

• eff = number of individuals/breeding couple
• bal = bowhead whale
• mer = little auk
• act = 21st century (current)
• hist = 17th century (historical)
• biom = Mesozooplankton biomass (expressed in tonnes)
• taux/prop = ratio
• conso / nonconso = consumed/not consumed
• acces = accessible
• aire = foraging area
• chevauchement = overlap
• poids = weight of each foraging factor
• densite = density

Here is a brief summary of column structure :

• Column 6 contains the main result = abundance of pre-whaling little auk populations.
• Columns 9 to 26 contain parameter values resulting from random draws for each Monte-Carlo repetition
• Columns 27 to 50 contain the main outputs for biomass consumption for both period of time and for both species
• Columns 51 to 78 contain various indicators computed with model outputs
• Columns 79 to 87 contain mesozooplankton biomass distribution among the different foraging areas
• Columns 88 to 159 contain detailed estimations of mesozooplankton biomass distribution among the different stratum (0.20m; 20.50m; 50.200m) and the different seafloor depth (20; 50; 100; 200; 6,000)

Variables per column (Col) correspond to :

• Col 1: Number of EGSB adult bowhead whales in the 21st century
• Col 2: Number of EGSB adult bowhead whales in the 17th century
• Col 3: Number of adult little auks in the 21st century
• Col 4: Number of little auk breeding pairs in the 21st century

• Col 5: Number of juvenile little auks in the 21st century

• Col 6: Number of adult little auks in the 17th century

• Col 7: Number of little auk breeding pairs in the 17th century

• Col 8: Number of juvenile little auks in the 17th century

• Col 9: Length of little auk breeding season (days)

• Col 10: Mean mesozoopkankton biomass simulated per cubic meter of water in the whole bowhead whale foraging area in the strata 0-200m (g/m2)

• Col 11: Ratio Production to Biomass as drawn by Monte-Carlo simulation

• Col 12: Proportion of annual secondary production achieved during the study period (%)

• Col 13: Proportion of copepods within mesozooplankton biomass (%)

• Col 14-16: Proportion (%) of the total mesozooplankton biomass in the water column within each stratum

•  Col 17: Daily mesozooplankton food requirements by an adult bowhead whale, averaged over one year (t.ww.day-1 with ww=wet weight and t=tonne)

• Col 18: Multiplication factor of bowhead whale food requirements during summer

• Col 19: Critical mesozooplankton biomass density threshold for bowhead whale foraging (g.m-3) 

• Col 20: Daily mesozooplankton food requirements by an adult little auk (g.ww.day-1 with ww=wet weight)

• Col 21: Mesozooplankton food requirements for a juvenile little auk between hatching and fledging (g.ww.)

• Col 22: Critical mesozooplankton biomass density threshold for little auk foraging (g.m-3)

• Col 23: Capture requirements of mesozooplankton individuals during subwater foraging by little auks (ind.s-1)

• Col 24: Mean wet weight of mesozooplankton individuals captured by little auks (mg.ww.)

• Col 25: Diving speed during foraging by little auks (m.s-1)

• Col 26: Foraging area around the beak from which little auks fully extract mesozooplankton biomass (m²)

• Col 27 and 28: Total mesozooplankton biomass consumed by EGSB bowhead whale population in the 17th and 21st centuries (tonnes)

• Col 29, 30 and 31: Total mesozooplankton biomass accessible to EGSB bowhead whale population in the 17th and 21st centuries (tonnes)

• Col 32: Total mesozooplankton biomass not accessible to EGSB bowhead whale population (tonnes)

• Col 33 and 68: Total mesozooplankton biomass within the EGSB bowhead whale foraging area (tonnes)

• Col 24 to 38: Share (%) of mesozooplankton biomass (accessible or total) eaten by bowhead whales in the 17th and 21st centuries 

• Col 39 and 40: Total mesozooplankton biomass consumed by the little auk population in the 17th and 21st centuries (tonnes)

• Col 41 to 47: Total mesozooplankton biomass accessible to the little auk population in the 17th and 21st centuries and eaten by whales (consobal) or not eaten by whales (nonconsobal) (tonnes)

• Col 48: Total mesozooplankton biomass not accessible to the little auk population (tonnes)

• Col 49 and 50: Total mesozooplankton biomass within the little auk whale foraging area in the 17th and 21st centuries (tonnes)

• Col 51 to 58: Share of accessible/total/within little auk foraging area that is consumed or accessible to little auks in the 17th and 21st centuries (%)

• Col 59 to 62: Percentage of overlap by one species over the other's trophic niche (%) in the 17th and 21st centuries (tonnes)

• Col 65 to 67: Weights (%) of the geography, depth and biomass threshold criteria in the difference in biomass accessibility between bowhead whales and little auks

• Col 69: Mean mesozooplankton density in the study area (g.m-3)

• Col 70: Percentage of water volume within study area that contains mesozooplankton patches (%)

• Col 71 and 72: Total mesozooplankton biomass within patches (tonnes) and percentage relatively to total biomass (%)

• Col 73 to 75: Total mesozooplankton biomass within each strata (0-20m, 20-50m, 50-200m)  (tonnes)

• Col 76 to 78: Mean density of mesozooplankton biomass within each strata (g.m-3)

• Col 79 to 82: Mesozooplankton biomass accessible to EGSB bowhead whales in subsets of the foraging area (Kara sea, Barents sea, Greenland sea, Arctic bassin) (tonnes)

• Col 83 to 87: Mesozooplankton biomass accessible to little auks in subsets of the foraging area (East Greenland, Svalbard, Novaya Zemlya, Jan Mayen, Franz Joseph) (tonnes)

• Col 88 to 195 contain the detailed estimations of mesozooplankton biomass (tonnes) generated by the model with the following characteristics : 

  • species : 'bal' (bowhead whale) or 'mer' (little auk)
  • centuries: 'hist' (17th century) or 'act' (21st century)
  • status: 'conso' (consumed), 'acces' (accessible to), 'nonconso' (accessible and not consumed), 'nonacces' (not accessible to)
  • ocean strata (0.20m; 20.50m; 50.200m)
  • seafloor depth (20; 50; 100; 200; 6,000)

Description of shapefile (sf_surfacewhaleauk_depth)

This shapefile contains geographical information (CRS = ESRI:102016 - North Pole Aziumthal Equidistant) about the 22,225 cells of 400 km² (20 x 20km) covering the study area : 

• Percentage (%) of the cell's surface within the four sea regions (Kara, Arctic, Barents, Greenland) and within the five little auk foraging areas (East Greenland, Svalbard, Novaya Zemlya, Jan Mayen, Franz Joseph) [NA equals to 0, meaning that the cell is completely outside of these areas]
• Mean seafloor depth (meters) from the  General Bathymetric Chart of the Oceans [cells with NA are cells unreported in GEBCO and therefore excluded from the analysis]

Description of coast.txt

This dataset contains the geographical information (lon = longitude, lat = latitude) to draw the coast lines and plot the copepod biomass estimation data from Drago et al. (2022) (see link below). 

Description of R script

The R script contains all the details necessary to follow the modelling steps described in the methods section of the article, aiming at estimating the pre-whaling little auk in the Atlantic Arctic. 

It starts with the Monte-Carlo simulations and ends with the final dataframe (PCBM_Results_XXXXXrep_XXXX-XX-XX.txt). All required packages are listed. All data needed to run the script are to be downladed here and using the github link below. 

Sharing/Access information

Simulations of the global distribution of copepod biomass from Drago et al., 2022 used as inputs in the model are available at https://github.com/dlaetitia/Global_zooplankton_biomass_distribution.git.

Code/Software

The model was created using R version 4.2.2