Fig 2. Chronic stress, measured by tank water cortisol, is reduced by social housing and pebble picture enrichment.
Both enrichment with pebble pictures (F1,10 = 7.171; P = 0.0232) and group housing (F1,10 = 9.8339; P = 0.0106) significantly reduced tank water cortisol. These effects were additive and equivalent, such that singly housed enriched tanks did not differ significantly from the barren, group housed tanks (F1,10 = 0.1049; P = 0.7527), and group housed zebrafish with pebble pictures had the lowest cortisol levels of all treatment groups. Data are plotted as LSM ± SE. * indicates significant differences between Barren versus Pebble enriched tanks.