International survey on the use and welfare of zebrafish Danio rerio in research

Abstract

A survey was conducted regarding zebrafish Danio rerio use for scientific research with a focus on: anaesthesia and euthanasia; housing and husbandry; breeding and production; refinement opportunities. A total of 98 survey responses were received from laboratories in 22 countries in Europe, North America, South America, Asia and Australia. There appears a clear and urgent need to identify the most humane methods of anaesthesia and euthanasia. Aversive responses to MS-222 were widely observed raising concerns about the use of this anaesthetic for D. rerio. The use of anaesthesia in fin clipping for genetic identification is widely practised and there appears to be an opportunity to further develop less invasive methods and refine this process. Optimization (and potentially standardization) of feeding is an area for further investigation. Given that diet and body condition can have such profound effects on results of experiments, differences in practice could have significant scientific implications. Further research into transition between dark and light phases in the laboratory appears to represent an opportunity to establish best practice. Plants and gravel were not considered practical by many laboratories. The true value and benefits need to be established and communicated. Overproduction is a concern both from ethical and financial viewpoints. There is an opportunity to further reduce wastage of D. rerio. There are clear concerns and opportunities for the scientific community to work together to further improve the welfare of these important laboratory models.

Shade as enrichment: testing preferences for shelter in two model fish species

“…Alternatively, the D. rerio in our study, unlike the G. aculeatus , were captive‐bred, had been used in a previous experiment (Jones et al ., ) and may behave differently to wild fish, particularly in response to stressors such as handling and movement between tanks (Huntingford, ). Moreover, captive‐bred fish may be less affected by standard laboratory lighting than wild‐caught fish, since they were raised with it (Villamizar et al ., ), although it can still be a major source of stress (Lidster et al ., ; Morgan & Tromborg, ). While our study found no apparent value to either form of shelter enrichment, even indicating that D. rerio may actively avoid shade or plants, it was relatively short‐term; longer periods of exposure to enrichment (gravel–plants) in D. rerio do show benefits in terms of both survivorship and female body condition (Lee et al ., ).…”

“…Environmental enrichment, both as a term and in practice, can take many forms and is often applied vaguely or inconsistently across studies -even within a well-studied species such as the zebrafish (Lawrence, 2007;Lidster et al, 2017). It should also be noted that enrichment preferences may vary between species (Kistler et al, 2011).…”

“…Despite the known benefits of physical enrichment, it may be costly or inconvenient to provide (Lidster et al, 2017). This has led to recent studies exploring possibilities for easily-implemented and lowcost alternatives, such as the exploration of the use of frequent water changes (Lee et al, 2018).…”

Ethical considerations in fish research

“…The addition of enrichment to tanks is often done to improve welfare, but the evidence that environmental enrichment promotes welfare in fishes is controversial, with many effects being species‐specific (Kistler et al ., ). In a recent survey of D. rerio facilities, less than 25% of facilities used environmental enrichment in the form of plants or substrate and were not considered practical by many of the laboratories surveyed (Lidster et al ., ). Motivational and preference tests are often used and can indicate if a species values the presence of enrichment (Sullivan et al ., ).…”

Can simple tank changes benefit the welfare of laboratory zebrafish Danio rerio?

“…Many environmental factors, however, can potentially affect an animal's physiology or behaviour (Killen et al ., ) and so influence research results. In addition, some forms of enrichment, such as the addition of plants and gravel, are considered impractical or costly by some laboratories (Lidster et al ., ) and, importantly, there are no studies describing the duration of benefit imparted by the addition of these physical items for fish and how they should be managed day to day with other husbandry practices. There is unquestionably the need for enrichment approaches that provide measurable welfare benefits without compromising research results.…”