Revision of Annexes III and IV of Directive 2010/63/EU on the protection of animals used for scientific purposes regarding accommodation parameters and methods of killing for zebrafish, and accommodation parameters for Passerine birds

This scientific Opinion evaluates the current state of the art considering key accommodation parameters to maintain the welfare of zebrafish in captivity for scientific purposes. In addition, euthanasia methods (e.g. hypothermic shock) for zebrafish were evaluated. Furthermore, housing requirements were evaluated for maintaining the welfare of a number of Passerine bird species kept in captivity. Sophisticated housing systems are available for zebrafish holding facilities such as flow- through and/or recirculating aquaculture systems. Water quality parameters were presented for zebrafish housing systems. The temperature range recommended for zebrafish housing systems is 24°C to 29°C, with an optimum temperature of 28°C, as is currently common practice. It is important to keep the noise level as low as possible and the light level constant, irrespective which light dark cycle (mostly 14/10 or 12/12 hours, light versus dark) is applied in the housing facility. Some form of enrichment (e.g. social, physical, visual, nutritional) in the system is recommended. In addition, health control measures should be in place to monitor for potential introduction of contaminants and pathogens causing disease. An optimal stocking density is 5 adult fish/L, whereas the maximum is considered 10 fish/L. The presence of less than 5 fish per tank is possible under certain conditions, however, this is not recommended for prolonged periods of time. Besides an overdose of anaesthetics, hypothermic shock, also known as rapid chilling, can be considered a reliable and safe method of euthanasia in zebrafish equal or older than 16 days post fertilization (dpf). A proper hypothermic shock protocol should be followed ensuring that no direct contact of the fish to the crushed ice is possible. Regarding Passerine birds, in this Opinion, ‘captivity’ is defined as holding birds within an enclosure (e.g. a cage or an aviary) that can be for short- or long-term periods. Both practically and physiologically, ‘short term’ can be justified as being up to one circadian cycle, i.e. up to 24 hours. Therefore ‘short term’ was defined as a period of 24 hours, for which the housing conditions may deviate from the conditions recommended in the Opinion. For Passerine birds in captivity beyond 24 hours, housing conditions were evaluated for starlings, sparrows and great and blue tits, as these are the most common Passerine birds used for scientific purposes. For starlings and house sparrows group housing is considered necessary. For great and blue tits in captivity, there is no preference for either being housed singly or in groups but in most situations single housing is preferable due to their territorial behaviour. In all cases, tits should have auditory contact with other conspecifics.