Guide for the Care and Use of Laboratory Animals - Office of ...

ENVIRONMENT, hOUSING, ANd MANAGEMENT 83housing for many species. When used, enrichment should elicit speciesappropriatebehaviors and be evaluated for safety and utility.Generally, schooling fish species are housed with conspecifics, andmany amphibians, especially anuran species, may be group housed. Aggressionin aquatic animals does occur (van de Nieuwegiessen et al. 2008;Speedie and Gerlai 2008) and, as for terrestrial animals, appropriate monitoringand intervention may be necessary (Matthews et al. 2002; Torreillesand Green 2007). Some species need appropriate substrate (e.g., gravel) toreproduce or need substrate variety to express basic behaviors and maintainhealth (Overstreet et al. 2000). Improved breeding success in enrichedenvironments has been reported but further research in this area is needed(Carfagnini et al. 2009). For many species (including, e.g., X. laeis), visualbarriers, hides, and shading are appropriate (Alworth and Vasquez 2009;Torreilles and Green 2007). Most semiaquatic reptiles spend some timeon land (basking, feeding, digesting, and ovipositing) and terrestrial areasshould be provided as appropriate.Sheltered, Outdoor, and Naturalistic housingAnimals used in aquaculture are often housed in situations that mimicagricultural rearing and may be in outdoor and/or sheltered raceways,ponds, or pens with high population densities. In these settings, wherenatural predation and mortalities occur, it may be appropriate to measureanimal “numbers” by using standard aquaculture techniques such as finalproduction biomass (Borski and Hodson 2003).SpaceSpace recommendations and housing density vary extensively with thespecies, age/size of the animals, life support system, and type of research(Browne et al. 2003; Green 2009; Gresens 2004; Hilken et al. 1995;Matthews et al. 2002). In the United States, for example, adult zebrafish(danio rerio) in typical biomedical research settings are generally housed 5adult fish per liter of water (Matthews et al. 2002), but this housing densityvaries when breeding and for housing younger animals (Matthews et al.2002). This guidance is not necessarily relevant for other species of fish, andmay change as research advances (Lawrence 2007). X. laeis adults maybe housed at 2 liters of water per frog (NRC 1974), but a wide variety ofhousing systems are currently used in research settings (Green 2009). Institutions,investigators, and IACUC members should evaluate the appropriateneeds of each species during program evaluations and facility inspectionsand continue to review ongoing research in these areas.