The COM DEC 2017/848/EU sets the criteria and methodological standards on good environmental status of marine waters and specifications and standardised methods for monitoring and assessment.
The selection of species and habitats to be assigned to the species groups and pelagic and benthic broad habitat types shall be based on the following:

1. Scientific criteria (ecological relevance):

  • representative of the ecosystem component (species group or broad habitat type), and of ecosystem functioning (e.g. connectivity between habitats and populations, completeness and integrity of essential habitats), being relevant for assessment of state/impacts, such as having a key functional role within the component (e.g. high or specific biodiversity, productivity, trophic link, specific resource or service) or particular life history traits (age and size at breeding, longevity, migratory traits);

  • relevant for assessment of a key anthropogenic pressure to which the ecosystem component is exposed, being sensitive to the pressure and exposed to it (vulnerable) in the assessment area;

  • present in sufficient numbers or extent in the assessment area to be able to construct a suitable indicator for assessment;

  • the set of species or habitats selected shall cover, as far as possible, the full range of ecological functions of the ecosystem component and the predominant pressures to which the component is subject; 

  • if species of species groups are closely associated to a particular broad habitat type they may be included within that habitat type for monitoring and assessment purposes; in such cases, the species shall not be included in the assessment of the species group.

2. Additional practical criteria (which shall not override the scientific criteria):

  • monitoring/technical feasibility;

  • monitoring costs;

  • adequate time series of the data.

The representative set of species and habitats to be assessed are likely to be specific to the region or subregion, although certain species may occur in several regions or subregions.