A sustainable integrated system for culture of fish, seaweed and abalone

A 3.3 m² experimental system for the intensive land-based culture of abalone, seaweed and fish was established using an integrated design. The goals were to achieve nutrient recycling, reduced water use, reduced nutrient discharge and high yields. Effluents from Japanese abalone (Haliotis discus hannai) culture tanks drained into a pellet-fed fish (Sparus aurata) culture tank. The fish effluent drained into macroalgal (Ulva lactuca or Gracilaria conferta) culture, and biofilter tanks. Algal production fed the abalone. The system was monitored to assess productivity and nitrogen partitioning over a year. The fish grew at 0.67% day^-1, yielding 28-kg m^-2 year^-1. The nutrients excreted by the fish supported high yields of U. lactuca (78-kg m^-2 year^-1) and efficient (80%) ammonia filtration. Gracilaria functioned poorly. Ulva supported an abalone growth rate of 0.9% day^-1 and a length increase of 40-66 μm day^-1 in juveniles, and 0.34% day^-1 and 59 μm day^-1 in young adults. Total abalone yield was 9.4 kg year^-1. A surplus of seaweed was created in the system. Ammonia-N, as a fraction of total feed-N was reduced from 45% in the fish effluents to 10% in the post-seaweed discharge. Based on the results, a doubling of the abalone:fish yield ratio from 0.3 to 0.6 is feasible. (C) 2000 Elsevier Science B.V.