Human exploitation of shellfish in the Atacama desert coast and environmental variability: a trans-Holocene perspective

Description

Table of contents

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This repository has the datasets used in Broitman et al., (in review) to investigate long-terms relationships between human harvesting, molluscan assemblages, and oceanographic variability along the coast of Taltal, northern Chile, from early Holocene to the present. It includes six complementary datasets comprising: 1) archaeological molluscan assemblage, 2) modern benthic assamblage, 3) modern fisheries assemblage, 4) taxonomic and ecological information, 5) oceanographic modern context and 6) palaeoceanographic thermal conditions.

The contents of each datasets are described below:         

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1) Archaeological molluscan assemblage (archae_molluscan_assem.csv)

The dataset archae_molluscan_assem.csv contains archaeological molluscan assamblage data from six study sites located along the coast of Taltal, northern Chile (see Broitman et al., submitted, for details). Taxon abundance is expressed as the Minimum Number of Individuals (MNI) for each species (Species column). 

For qualitative and quantitative analyses, archaeological assemblages were assigned to the six chronocultural stages (Archaic 1-6) proposed by Salazar et al., (2015), which are recorded in the Archaic column.

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2) Modern bentihc assamblage (modern_benthic_assem.csv)

The dataset modern_benthic_assem.csv contains data on modern benthic molluscan assemblages recorded from five rocky shore sites adjacent to the archaeological sites north of the city of Taltal (including Taltal site).

The dataset includes the following columns:

• Site: Name of the sampling site.
• Transect: Identifier of the transect surveyed at each site (1 and 2).
• Date: Date on which the survey was conducted.
• Year: Year of sampling.
• Area: Surface area surveyed (m²) on each rocky shore platform.
• Species: Scientific name of the species recorded at each survey.
• Count: Number of individuals of each species recorded within the surveyed area.
• Height: Intertidal shore height (middle and lower shores), at which the transect was surveyed.
• Density: Density of each species (individuals m^-2), calculated from the number of individuals (Count) and the surveyed area (Area).

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3) Modern fisheries assemblage (fisheries_modern_timeseries.csv)

The dataset fisheries_modern_timeseries.csv summarises the annual artisanal landings of benthic marine organims recorded by scientific observers of the Instituto de Fomento Pesquero (IFOP; National Fisheries Development Institute) from two small fishing ports in the Taltal area, northern Chile (see Broitman et al., submitted, for details). Data collection methods are fully described by Chevallier et al., (2020).

The dataset includes the following columns:

• Fisheries: Fishery category assigned to each species according to its functional ecological group.
• Year: Year of the recorded landings.
• Sum_landings: Total annual landings (tonnes) for each functional ecological group.

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4) Taxonomic and ecological information (species_taxonomy_fishery.csv)

The dataset species_taxonomy_fishery.csv provides the taxonomic classification (Species, Class, Order, and Family) and ecological information (Fishery column: functional group to which each taxon was assigned for analyses) for all species recorded in the following datasets:

• archae_molluscan_assem.csv
• modern_benthic_assem.csv
• fisheries_modern_timeseries.csv

This dataset serves as a reference table linking species taxonomic classification and ecological groupings across the archaelogical, modern benthic and fisheries datasets.

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5) Oceanographic modern context (modis_sst_annual.csv)

The dataset modis_sst_annual.csv contains annual Sea Surface Temperatures (SST) metrics derived from the Moderate Resolution Imaging Spectrodiometer (MODIS) for the period 2003-2021 (see Broitman et al., submitted, for details). SST data were obtanained from the NASA Ocean Color repository at a spatial resolution of 4 x 4 km and were used to examine the relationship between contemporary oceanographic conditions and the abundance of annual artisanal landings of benthic marine organims (fisheries_modern_timeseries.csv).

The dataset includes the following variables:

• Year: Calendar year (2003 to 2021).
• p5_SST: Annual 5th percentile of SST (°C).
• p50_SST: Annual 50th percentile of SST (°C).
• p95_SST: Annual 95th percentile of SST (°C).

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6) Palaeoceanographic context (archae_periods_sst.csv)

The dataset archae_periods_sst.csv contains Sea Surface Temperatures (SST) estimates reconstructed from δ18O measurements of carbonate shells of the keyhole limpet Fissurella maxima, as published by Flores et al., (2018). SST estimates were summarised for each archaeological period and were used to examine the relationship between Holocene oceanographic conditions and changes in fisheries through time.

The dataset includes the following variables:

• Archae_period: Archaeological periods (1-6).
• Age_start: Start of the archaeological period (years before present). 
• Age_end: End of the archaeological period (years before present).
• N: Number of chronological dates included for each archaeological period. 
• p5_SST: Annual 5th percentile of reconstructed SST (°C).
• p50_SST: Annual 50th percentile of reconstructed SST (°C).
• p95_SST: Annual 95th percentile of reconstructed SST (°C).
• Variance: Variance of reconstructed SST (°C).

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