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Human-wildlife interactions on the tidal flats of the Bijagós archipelago: does shellfishing affect migratory shorebirds?

Cite this dataset

Coelho, Ana (2024). Human-wildlife interactions on the tidal flats of the Bijagós archipelago: does shellfishing affect migratory shorebirds? [Dataset]. Dryad. https://doi.org/10.5061/dryad.2ngf1vhtk

Abstract

The Bijagós archipelago in West Africa is home to an ethnic group with a rich cultural heritage that is tightly linked to nature. The Bijagós people have a shared cultural identity, but across islands, there are different resource management regimes stemming from island-specific context with regards to socio-political organization and strength of cultural heritage. Across the archipelago, bivalves harvested manually from the mudflats are an important part of the Bijagós people’s diet, economy, and culture. Thousands of migratory shorebirds share the use of these mudflats during their non-breeding season, consuming macrobenthos such as crustaceans and bivalves, including those harvested by local people. At the end of their stay in the Bijagós, shorebirds need to fuel for their migratory flight in order to return to their breeding areas, being particularly important during this period that they have access to undisturbed feeding areas with suitable food resources.

In this study, we start by exploring shellfishing patterns across different management regimes, then assess seasonal variation in the direct impact of shellfishing on shorebirds (through competition for resources and space), and finally quantify the indirect impact of sediment disturbance due to shellfishing upon shorebird prey availability. Results indicate that bivalve resources are better managed in areas with formal protection, while traditional management based on cultural beliefs results in poorer stock conditions. Interestingly, across islands shellfishing activity is concentrated in mid-winter, decreasing towards shorebirds’ fuelling period, when they benefit the most from reduced disturbance on the mudflats. No direct competition for resources was detected, as collected bivalves were significantly larger than those consumed by shorebirds, regardless of the season. Indirect impacts caused by sediment disturbance during shellfishing were also mostly absent, causing only a small reduction on shorebirds prey density, but with no effect on the available biomass.

README: Title of Dataset

Human-wildlife interactions on the tidal flats of the Bijags archipelago: does shellfishing affect migratory shorebirds? Give a brief summary of dataset contents, contextualized in experimental procedures and results.

Description of the data and file structure

Data is structured in 3 separate sheets, refering to 3 different methodologies, described in the methods section of the main article.

Description of "Hand-raking experiments" sheet:

  • Column "Species" refers to the hand-raked bivalve species (Comb or Lingron)
  • Column "Treatment" refers to the treatment of the plot (T = treated plot by hand-raking the sediment and colection of the target bivalve, C = control plot, not hand-raked)
  • Column "Day" refers to the time of sample collection (Day 1 = The day of the experiment; Day 15 = 15 days after the experiment; Day 0 = experimental plot hand-raked before receiving the treatment later that day)
  • Column "Core" refers to the numer of the collected sediment core (sequencial from 1 to 7)
  • Column "position" refers to the position of the sediment core sample (T= top 5cm of
  • the sediment corer; B = Bottom 10 cm of the sedimente corer)
  • Column "point" refers to the sampling point specific code (7 points collected in each plot/treatment)
  • Column "storage" refers to where the stogare code for posterior consultation (storage "field" refers to individuals measured in the field and not stored)
  • Column "sp" refers to the macrobenthos taxa found in the sediment sample Column
  • "TL" refers to the Total Length (in mm) of each individual found in the sediment sample

Description of "Bivalve Size Measurments" sheet:

  • Column "Date" refers to the date when the bivalve was measured
  • Column "period" refers to the period of the migratory shorebird's stay in the Bijagos (Wintering or Fuelling, see methods on paper for further detail)
  • Column "site" refers to the site where the measured bivalve was collected
  • Column "species" refers to the species of the bivalve measured
  • Column "TL" refers to the Total Length (in mm) of each individual bivalve measured

Description of "Mudflat presence"

  • Column "Date" refers to the date when the number of people on the mudflats was counted
  • Column "period" refers to the period of the migratory shorebird's stay in the Bijagos (Wintering or Fuelling, see methods on paper for further detail)
  • Column "site" refers to the site where the number of people on the mudflats was Counted
  • Column "time" refers to the time when the number of people on the mudflats were counted
  • Column "n" refers to the number of people of each category counted
  • Column "gender/age" refers to the social category of people present of the mudflat (W = women, M = man; K = kid)
  • Column "activity" refers to the activity each category of people was performing on the mudflat