Optimal density of Asian seabass (Lates calcarifer) in combination with the Omani abalone (Haliotis mariae), brown mussel (Perna sp.) and seaweed (Ulva fasciata) in a land-based recirculating integrated multi-trophic aquaculture (IMTA) system

An experiment was conducted to develop a land-based recirculating integrated multi-trophic aquaculture (IMTA) system using a combination of the Omani abalone (Haliotis mariae) and Asian seabass (Lates calcarifer) as fed species, brown mussel (Perna perna) and seaweed (Ulva fasciata) as extractive species. Specifically, this study was carried out to determine the optimal seabass density (20, 40 and 60 individuals per 500-liter tank) on water quality, growth and survival of the cultured species in the system. Sampling of all species was done every two weeks to check their growth. Water samples were taken every two weeks for analysis of ammonia, nitrite, nitrate, phosphate, and sili- cate. Measurements of temperature, dissolved oxygen and salinity were done daily. Growth of abalone and mussels were higher in fish densities of 20/tank and 40/tank, respectively, while growth and survival of seabass were not significantly different between densities. Biomass of seaweeds decreased during the experiment period. Temperature, dissolved oxygen and salinity were within optimum levels. Ammonia levels decreased as nitrite increased but in some cases it remained high while nitrates did not increase, indicating that nitrites were not converted to nitrates most likely due to the lack of efficient bio-filtration in the mussel tanks.