To cite package ‘zooimage’ in publications use:

  Grosjean P, Denis K, Wacquet G (2018). _zooimage: Analysis of
  Numerical Plankton Images_. R package version 5.5.2,
  <https://CRAN.R-project.org/package=zooimage>.

A BibTeX entry for LaTeX users is

  @Manual{,
    title = {zooimage: Analysis of Numerical Plankton Images},
    author = {Philippe Grosjean and Kevin Denis and Guillaume Wacquet},
    year = {2018},
    note = {R package version 5.5.2},
    url = {https://CRAN.R-project.org/package=zooimage},
  }