DOI: 10.5061/dryad.9s4mw6msb
title: Mortality drives production dynamics of Atlantic cod through 1100 years of commercial fishing

description: Most edible fish species have been fished for centuries or millennia,
 leaving little record or understanding of their population responses prior
 to human impact, and thus no baseline for population conservation. Here,
 we reconstruct the population dynamics of Atlantic cod, one of the world’s
 most harvested fish species, from the pristine state during the Viking era
 through more than 1100 years of fishing. Analysis of cod otoliths
 recovered during archaeological excavations of Icelandic fish processing
 sites revealed that cod in the 10th to 12th centuries were 25% larger and
 up to 300% older than modern, despite slower density-dependent growth
 rates attributed to the 6-fold increase in abundance. Fishing mortality
 came to dominate a time-invariant natural mortality rate and other
 population characteristics after the 14th century, with minimal evidence
 of environmental effects at the century scale. Despite the absence of
 catch records and surveys, biological reference points based on pristine
 fish populations are now possible where otolith collections are available.
description: # Mortality drives production dynamics of Atlantic cod through 1100 years
 of commercial fishing
 [https://doi.org/10.5061/dryad.9s4mw6msb](https://doi.org/10.5061/dryad.9s4mw6msb) ## Description of the data and file structure The dataset includes measurements and estimates derived from collections of archaelogical and modern Atlantic cod (Gadus morhua) otoliths from Iceland. Methodological details are provided in the Campana et al Science Advances paper. Three data files are provided: otoliths archaeological Campana.csv:  Measurements of individual otoliths from the archaeological otoliths otoliths modern and archaeological for length and age Campana.csv:  Length, age and growth estimates from both the archaeological otoliths and those from a subsample of modern collections from the study area. The archaeological data are the same as those provided in the file otoliths archaeological Campana.csv cod estimates by century Campana.csv: Century-scale aggregates and estimates of modern and archaeological otoliths Please note that all three datasets include some missing values (due to otolith damage or missing ages). Missing values have been left blank. ### Files and variables #### File: otoliths\_modern\_and\_archaeological\_for\_length\_and\_age\_Campana.csv **Description:**  ##### Variables * Source: Source of otoliths was either archaeological (Archaeo) or modern (a subsample of the Years 2000-2010) from the hook and line fishery (hooks) or research vessel trawl survey in the fall (RV Fall) or spring (RV Spring) * Historical_or_modern: Archaeological or modern otolith * CAMHID: Fish identification number * Year: * Century: * Century_recoded: Century variable which aggregates 13th and 14th centuries into 13.5 * Length_cm: * Age_yr: * Predicted_length_cm: Predicated length at age from von Bertalanffy growth model * G_index: Growth index as described in paper; observed length divided by predicted length * Region: West (W) or Northwest (NW) #### File: cod\_estimates\_by\_century\_Campana.csv **Description:**  ##### Variables * Century: * century_recoded: Century variable which aggregates 13th and 14th centuries into 13.5 * CC_Z: Mortality rate estimate (Z) from catch curves (CC) * CC_SE_Z: Standard error (SE) of mortality rate estimate (Z) from catch curves (CC) * CR_Z: Mortality rate estimate (Z) from Chapman Robson estimator (CR) * CR_SE_Z: Standard error (SE) of mortality rate estimate (Z) from Chapman Robson estimator (CR) * Z: Instantaneous mortality rate (Z) calculated as mean of CC*Z and CR*Z, weighted by inverse of SE * Z_SE: Standard error of Z estimate * N: Number of otoliths * TotalCatch_000t: * DomesticCatch_000t: * ExportedCatch_000t: * ForeignCatch_000t: * HumanPop_000: * G_index: Growth index as described in paper; observed length divided by predicted length * Adult_abundance: Index of adult (age 6+) cod abundance * d13C_emm: Estimated marginal mean (emm) of d13C from general linear model * d18O_SS_emm: Estimated marginal mean (emm) of d18O from general linear model using only SS otoliths * d18O_CAMH_emm: Estimated marginal mean (emm) of d18O from general linear model using only CAMH otoliths * O18_Reynolds: d18O time series from Reynolds et al (2017), *Palaeogeogr. Palaeoclimatol. Palaeoecol.* **465**, 333-346. #### File: otoliths\_archaeological\_Campana.csv **Description:**  ##### Variables * Data_source: Otolith source (CAMH, SS or GUD) * CAMHID: Otolith identification number * Site: Archaeological site * SiteCode: Archaelogical site code * Region: W (west) or NW (northwest) * Year: * Century: * century_recode: Century variable which aggregates 13th and 14th centuries into 13.5 * d13C_whole_oto: d13C of either whole otolith or age-aggregated section * d18O_whole_oto: d18O of whole otolith or age-aggregated section * d13C_juv: d13C of juvenile portion of otolith section (SS otoliths only) * d18O_juv: d18O of juvenile portion of otolith section (SS otoliths only) * d13C_adult: d13C of adult portion of otolith section (SS otoliths only) * d18O_adult: d18O of adult portion of otolith section (SS otoliths only) * Age_yr: * Oto_section_diameter_mm: Diameter of otolith section from tip to tip * Estimated*fishlengthcm: Fish length as estimated from relationship of otolith*-section diameter and fish length * VonB_fishlength_cm: Fish length at age from von  Bertalanffy growth model * VonB_residual: Residual from estimate of fish length at age from von  Bertalanffy growth model * G_index: Growth index as described in paper; observed or estimated length divided by vonB predicted length * O18_Reynolds: d18O time series from Reynolds et al (2017), *Palaeogeogr. Palaeoclimatol. Palaeoecol.* **465**, 333-346.