The Commission Decision 2017/848/EU established two primary and two secondary criteria for the status of food webs:
MS reported in the first cycle (2012) a number of methods per indicator and criteria. The most frequently reported methodologies for D4 were:
  • Reproductive performance (success, ability, rate) of bird, marine mammals, etc
  • Biomass and abundance of higher trophic level
  • Structure of population of main trophic group
  • Different measures or indices related to the proportion of large fish (by length or weight)
  • Proportion of fish at the top of the food web
  • Abundance and biomass of different components of the food web (zoo, fish, dolphins, sharks, birds)
  • Analysis of size structure of fish populations
  • Species/specific trends in relative abundance of species
  • Composition of phyto and zooplankton assemblages
In April 2014, ICES facilitated a Workshop to develop recommendations for potentially useful food web indicators (WKFooWI). The workshop built on progress already made to support Descriptor 4 through a joint JRC/DG ENV task force ( MSFD Task group 4 Report "Food webs" (2010)) and the findings from the first implementation cycle. The main findings and recommendations of this workshop are publically available:
Additionally, the DEVOTES FP7 project has developed a software tool to help selecting indicators for the MSFD: the DEVOTool. Among the list of scientific indicators compiled, several are potential tools that can be used to assess environmental status under D4.

The work on D4 is in progress, leaded and monitored by the MSFD Common Implementation Strategy groups, aiming to provide coherent, comparable and robust solutions for the the D4 assessment and monitoring.