Effects of simple shelters on growth performance and welfare of rainbow trout juveniles

Environmental enrichment is a promising strategy to improve the welfare of fish in captivity. However, utilization aquaculture still infrequent, maybe because there paucity knowledge about how its effects depend on factors such as species, developmental stage, social environment or type and extent enrichment. In this study, we evaluated physical rainbow trout juveniles, by exposing them simple plastic screen shelters. Juveniles approx. 15 g were introduced two types submerged shelters: full screens (Full) partial (Semi), was assessed compared control group (without shelters) evaluating growth condition, external lesions, neuroendocrine responses acute repeated stress. During eleven-week experimental period, sheltered units gradually developed clear shelter-seeking behavior when exposed disturbance. Fish growth, condition factor mortality not affected shelter presence. The presence shelters had modest protective effect fin damage: both pectoral fin- total damage scores reduced (> 10%) with respect group; percentage severe Full Control (63% vs 82%). Partial no significant scores, group. did affect general level stress upon standardized stressors. used showed more intense startling response stressors that forced abandon protection. Altogether, study shows potential for be welfare-promoting farming, but further research needed optimize design proper timing application.