Habitat-enhanced recirculating aquaculture systems improve post-transport recovery and survival of Scylla serrata (Forsskål, 1775)

Mud crab aquaculture is expanding rapidly, but its potential is constrained by high mortality rates linked to post-transport stress and suboptimal rearing systems. The industry’s reliance on prolonged transport and clear-water recirculating aquaculture systems (RAS) is fundamentally misaligned with the physiology of Scylla serrata, the Indo-Pacific’s most widely farmed crab species. This study evaluated a habitat-enhanced RAS designed to mimic estuarine conditions through the use of mud substrate, turbid water and shelters to address these challenges. Crabs subjected to transport durations of 0 h, 24 h and 48 h were reared in either conventional clear-water or naturalised RAS. Extended transport significantly increased Vibrio spp. loads in haemolymph and tissues, induced gill damage and suppressed immune function. In contrast, naturalised RAS substantially improved outcomes, achieving 80 % survival even after 48 h of transport. These systems also enhanced key health indicators, including immune parameters (total haemocyte count, phenoloxidase) and antioxidant capacity (superoxide dismutase, glutathione peroxidase), while simultaneously increasing moulting frequency and growth rates compared with clear-water controls. Kaplan-Meier analysis further confirmed a significantly lower mortality risk in naturalised systems. Collectively, these findings demonstrate that adopting naturalised, species-specific RAS designs is a viable and critical strategy for mitigating transport stress, improving animal welfare and ensuring the long-term sustainability of mud crab aquaculture.