In a laboratory setting, it is important to provide housing that allows expression in a wide range of species-typical behaviors while also meeting the goals of the researcher. Substandard housing can lead to aggression, stereotypic behavior, anxiety and depression which will, in turn, affect research outcomes. Understanding the animal’s natural behavior, enables us to build quality environments that meet physical, behavioral and social needs. Proper design is critical for improved health and welfare, both of which impact scientific validity.

Making changes to current housing standards can be challenging especially since facilities may be at very different levels of current housing. Start making small changes from where your facility is currently to improve. Also keep in mind that some of the recommendations below (e.g., providing certain types of environmental enrichment) can change some specific experimental models.

Before implementing housing changes, be sure to consult the relevant scientific literature and consider the requirements of your scientific model. Each facility may require an individual approach to increasing housing standards as much as possible.

Technicians should be able to effectively clean housing areas, access individual animals, and complete behavioral observations. Those working with zebrafish should receive proper training in the natural history of the species, how to recognize species-typical & atypical behaviors, and appropriate methods for interacting with the animals in their care.

Zebrafish In Tank
Zebrafish Close-up

Key Natural Behaviors of Zebrafish

  • Highly social species
  • Shoal in small, mixed sex schools of 6-300 fish
  • Form dominance hierarchies with potential for aggressive interaction
  • Found in areas with abundant aquatic vegetation for spawning and cover from predation
  • Eat primarily zooplankton and insects and engage in foraging behaviors
  • Olfaction is dominant sensory modality
  • Diurnal
  • Prefer structural complexity
  • Will occupy entire water column

Recommendations

Social Housing

  • Larval and juvenile fish should be housed separately from adults
  • House in mixed-sex groups to prevent egg-binding in females
  • Recommended housing density of 5-20 adult fish per liter to reduce stress
  • Pair housing should be avoided
  • Single housing should be avoided
    • If single housing is necessary for scientific aims: fish should be placed in visual contact adjacent to conspecifics to help alleviate some of the stress of social isolation and provided with additional structural enrichment (artificial plants, shelters)
    • Females should be allowed to spawn at least once every 2 weeks to prevent becoming egg-bound

Tank Enclosure

  • Control water flow based on the age of fish (low to no flow for larval stages and increased rates of flow for adults)
  • Tanks should be large enough to allow for species-typical swimming and schooling behavior
  • Provide enrichment: artificial plants, shelters, mirrored paper on half of tank
  • Gravel substrate (use with caution in recirculating tanks) or picture of gravel substrate rather than barren tank bottom (Krueger et al., 2020)

Water Quality

  • Must be stable and free of contaminants
  • Aquaculture system must be maintained and regularly monitored to ensure proper water quality
  • Recommended Water Quality Parameters (page 90 Harper and Lawrence, 2011)

Feeding

  • Provide live feed (e.g. rotifers, brine shrimp) in addition to standard diet to adult fish to promote foraging behavior

Handling

Prevent injury to protective mucus layer on skin by:

  • Minimizing handling & transport time
  • Using a dark opaque scoop for transfer rather than a net
  • Keeping the skin of the fish moist whenever they are removed from water
  • Wearing fresh gloves and keep gloves moist when handling

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