ABSTRACT
Production predictions from various sources confirm further increases in global production from Aquaculture. By the end of the century this production is expected to reach 25 million metric tonnes per year. Significantly this increase is expected to be realized through the ongrowing of mainly high value species from the marine and brackish water environments. The technology employed to attain this type of current production is largely through using holding containers under more or less controlled conditions. The degree and extent of the control is the primary theme of this paper. The open system of production has long been the dominant method of ongrowing to date and owes much of this success to the integral support made by the many established enclosed onshore systems. The relationship between the two types of system is brought out and illustrated. Acceptable, ongrowing systems of the future will have to withstand scrutiny from many bodies as they compete for this prime, valuable and diminishing natural resource world-wide. Therefore in addition to the many environmental factors to be considered, current and new legislative restraints will have to be faced by new technology and examples of these are outlined here. A broad review of the enclosed production systems is contained in the paper and is illustrated by way of reference to different operational units in a variety of locations. Operational practices and performance of such systems are explained by example. In so doing the general advantages of the enclosed production system of ongrowing are emphasised. By comparing and contrasting these with those currently available by open production systems, the basic differences in the two systems are broadly outlined. In conclusion the review concentrates on the need to consolidate on the merits of enclosed systems and stresses the need to build on these to facilitate the creation of more new economically viable enclosed production units in the future.
