Severity classification in zebrafish and their larvae

The European Directive 2010/63 requires that the severity of all procedures is assessed prospectively and that the severity experienced for each animal used in procedures is recorded retrospectively. A scheme for severity classification is defined in Annex VIII of the Directive and a Commission Expert Working Group has published some guidance and examples for mammals in a framework document. These documents are of limited help in the context of the aquatic laboratory. Zebrafish, Danio rerio, is a good example of a widely used aquatic laboratory species in need of guidance. Housing conditions, feeding and water quality vary across aquatic facilities. Husbandry will have impact on survival at different ages. This must be differentiated from procedural mortality and severity. The severity classification of genetically altered phenotype is particularly influenced by pertinent laboratory strategies and welfare assessment The aim of the working group will be to identify current use of zebrafish and to propose guidance and examples to help with the procedural severity assessment in both adult and larval stages of zebrafish.