Lobsters can be successfully held and fattened in land-based holding systems provided suitable environment is provided. Critical environmental parameters include the concentration of dissolved oxygen, ammonia, nitrite and carbon dioxide.
Nitrate concentration, pH, salinity and alkalinity levels within the system are also important. In flow through systems, the main limiting factor is dissolved oxygen. The requirement of oxygen will be high during molting and soon after feeding. Both the process normally takes place during night and optimum levels of oxygen shall be maintained during night to avoid oxygen depletion and mortality.
Oxygen related stress would adversely affect growth significantly. Unlike shrimps, lobsters are oxygen conformers and may not show any sign of low oxygen conditions, as they are capable of adjusting the metabolism even at very low levels of oxygen. Sufficient water needs to be pumped through or the water needs to be aerated to ensure lobsters are supplied with sufficient oxygen. Sudden salinity fluctuation during rains is serious situation and in such circumstances salinity, alkalinity and pH should be adjusted in a reservoir, before the water is pumped in. though lobsters can tolerate gradual changes in salinity to a limited range, sudden dilution can lead to stress, susceptibility to disease and mortality.
Two main systems are currently being used for fattening lobsters: flow-through and recirculating. In flow through systems, the water that is pumped into a tank is used only once. Water flow is to be decided based on the stocking density and feeding intensity. The incoming water is to be free of sediments and should have water quality parameters required for lobster farming.
The water should be regularly monitored to avoid wide fluctuations in environmental parameters. In recirculating systems, the majority of the water is re-used after each pass-through the tanks, first being treated to remove waste products before being returned to the tanks. Even though initial set up costs may be higher, there is an increasing interest in the use of recirculating systems.
In recirculating systems also the main limiting factor is dissolved oxygen: however, the unionized ammonia concentration becomes increasingly important, and is probably the next important limiting factor. Ammonia should be removed from the system at a rate equal to the rate of production to maintain safe concentration.
All recirculating systems remove waste solids, oxidize ammonia and nitrite, remove carbon dioxide, and aerate the water before returning it to the fattening system.
Solid wastes can be removed by mechanical filtration, ammonia and nitrite by biological filtration and carbon dioxide by the provision of an air/water interface. The safe level of ammonia for holding lobsters is <2 mgL-1. The flow rate calculations must be adjusted according to the species held, size of the animals, the rate of feeding and the holding temperature.