Pseudo-green water as a potential enhancer of growth and coloration in European lobster, Homarus gammarus, larvae

Depleting European lobster, Homarus gammarus, wild stocks from historic overexploitation, stock enhancement programs, and farming of this lucrative species are viable options for meeting consumer demand. Early larval stages pose a hatchery challenge because of low survival rates. This study evaluates pseudo-green water benefits during the larval stage. Commonly used aquaculture algal species, Tetraselmis suecica (TS), Dunaliella tertiolecta (DT), and Nannochloropsis sp. (N), were tested as a monoculture or mixture treatment over 13 days post-hatching of the lobster larvae, from this, seven treatment permutations (TS, DT, N, TS + DT, TS + N, DT + N, and TS + DT + N) were included. A further eighth treatment with no added algae was used as a basal reference point (control). The growth assessment found that co-culturing had benefited carapace length and shell coloration (cephalothorax, p = 0.023) but no enhancement to the weight or survival ratios was observed. All larvae reached stage III by the 13th day, with survival rates ranging between 12.5% and 20%. Results indicated that mixed algal species generally had higher mean growth perfromance values than monoalgal cultures and clearer water. Nannochloropsis sp. significantly improved growth performance (higher weight and length). Algal matrices containing Nannochloropsis sp. resulted in the highest growth performance, emphasizing the importance of co-culturing lobster larvae with algae to improve hatchery operations.