INTRODUCTION
Aquaculture market projections uncover a large supply-demand imbalance in the next three decades. Focusing on fin fish supply specifically uncovers that output level is close to a saturation point for traditional areas with traditional aquaculture. As a result of the current situation fish farming is growing out of sheltered, near-shore areas and moved to more exposed locations and further offshore. Several innovative solutions are being tried out in ocean fish farming in the process of industrialization.
MAIN APPROACH
The numerous concepts planned and implemented may be split into four main categories: Open trusswork with traditional net or grating, semi-closed units, closed aquaculture installation and submerged solutions. All these concepts may be operated with permanent manning or a combination of remote operation and daily visits. This paper supply a specific description of the main solutions applied in the development of ocean farming:
Open trusswork. Further development of the traditional sheltered net pen usually with rigid floating collar in steel or concrete. Additional structural arrangements for additional buoyancy, ballasting/de-ballasting and distention of net panels are common features. This category may be split into two sub-sets. One includes operating at the ocean surface only while an increasing number of designs have the option of submerged position to avoid splash-zone dynamics at rough sea states.
Semi-closed units. These designs aim to separate fish environment from sea for the first few meters of the water column. This separation is established to protect fish from parasites living in the upper levels of the water column. Sufficient water circulation to maintain sufficient growing condition and fish welfare is often a change for these solutions.
Closed fish farming units. A wide variety of solutions are currently being explored in this category. The ability to control quality of water intake to optimize fish environment combined with possibility to collect fish waste and feed surplus promote the applicability of this solution. Water may be cleaned and re-cycled or filtered before emitting to sea resulting in less environmental impact per unit biomass. Establishing full separation between fish environment and sea results in less parasites and disease in addition to absolute fish control (no escape) and controlled aquaculture emissions to marine environment.
Submerged fish farming pens. An increasing number of designs have the option of submerged position to avoid splash-zone dynamics at rough sea states. This results in added operational complexity as operations such as feeding, dead fish retrieval and similar needs to be conducted remotely from the surface position.
Concepts and solutions listed have several advantages and weaknesses that must be considered and evaluated. In addition to applying steel and concrete as construction materials, several solutions are currently being built in novel materials such as polymers and composites. To reduce risk, utilizing these solutions sspecial focuses on structural integrity and manufacturing quality is needed. This involves a systematic approach across stakeholders to build trust. This work maps out essential items to be considered as qualification of polymer or composite built installations are qualified for safe operations in a demanding marine environment.
The essential parameters to be taken into consideration assessing performance are considered to be: Oxygen level in sea water, crowding and live transfer of fish, dead fish handling and ensilage processing, logistics of supplies and goods going both on and off the fish farming installation and personnel safety.