Larval fish transport: enhancing protocol to increase fish welfare and survival in Meagre (Argyrosomus regius)

There is an increasing interest in high-value marine finfish, with the expansion of aquaculture. The transportation of early-life stages, especially fertilized eggs, from hatcheries to aquaculture and research facilities is a commonplace procedure. However, challenges such as low hatching rates and mortality were observed during egg shipment due to factors like high stock density, extended shipping times, physical shocks, and water quality issues. Shipping yolk sac larvae may offer a potential solution to address these challenges. This research aimed to develop an accessible, user-friendly, and adaptable protocol for shipping yolk sac larvae, focusing on critical factors such as stocking density and transport duration. Three larval concentrations (4000 larvae L-1, D4; 8000 larvae L-1, D8; 12000 larvae L-1, D12) from two spawning events of meagre (Argyrosomus regius) were tested in replicates at three different simulated shipping times of (24h, ST24; 36h, ST36; 48h, ST48). Post-shipping survival was monitored within incubators for 24 hours. Results indicated successful transportation for all tested densities within ST24, with average (±SD) survival rates of 69 ± 2.47% for D4, 81± 4.24% for D8, and 80 ± 10.96% for D12. Higher densities (D8 and D12) exhibited higher survival rates at unpacking during ST24. Additionally, D4 showed transport viability within all tested shipping times, with an average(±SD) survival rate of 72 ± 12.30%. Surprisingly, D4 showed the highest average (±SD) survival rate of 85 ± 1.47% at ST48. While water quality showed no significant impact on larval survival during ST24, extended transportation emphasized the importance of maintaining optimal temperature and oxygen levels. The results underscore the need for species-specific considerations in larval transportation protocols. The stock densities and shipping duration tested in this study were important steps in improving long-distance transport protocols and pushing the limits of the early life stage of shipping marine fin fish.