Zebrafish preference for enrichment depended on enrichment position and social housing.

a) Singly housed zebrafish preferred enrichment regardless of position (T_1,43 = 4.51; P<0.0001); group housed zebrafish only preferred enrichment in the back of the tank (F_1,43 = 17.98, P = 0.0001). b) Preference did not differ between visual enrichment type (pebble picture versus visual access to conspecifics) (F_1,43 = 0.7686; P = 0.3855). Data depict singly and group-housed fish and are plotted as LSM ± SE. * indicates LSMs with a significant preference versus the null hypothesis of no preference (dashed line).