Turbot are flatfish increasingly farmed in intensive recirculating systems, where welfare challenges include stocking density, substrate absence, and handling stress during grading operations.
Turbot aquaculture presents specific welfare challenges arising from the mismatch between natural benthic behaviour and intensive tank culture. In the wild, turbot lie on sandy or gravelly substrates where they are camouflaged and secure; bare tank floors deprive them of this resting environment, and high densities lead to individuals resting on top of each other — abnormal behaviour indicating compromised welfare. Research has demonstrated that turbot show physiological stress responses to crowding and handling, with cortisol elevation persisting for hours after disturbance events such as grading. Grading operations, which separate fish by size to equalise growth, involve netting, air exposure, and physical handling — significant welfare insults. Substrate provision has been shown to improve behaviour and reduce stress indicators. Improving welfare standards in turbot aquaculture requires implementation of density limits, substrate provision, and less traumatic grading methods including automated systems that reduce handling time.