VESSEL REVIEW | Caijin Haishang Liangcang Yi Hao-1 – Large, submersible salmon pen to be deployed in China’s offshore waters

Chinese company Shandong Caijin Wanzefeng Marine Technology has completed construction of a submersible fish pen for harvesting salmon in offshore waters.

Caijin Haishang Liangcang Yi Hao-1 (财金海上粮仓壹号-1; “Caijin Offshore Granary No 1-1”) is the first of a planned series of six offshore salmon pens, all of which are scheduled to be operational in the Yellow Sea off the coast of eastern China by 2025 as part of a CNY300 million (US$41.4 million) investment. The goal of the deployment of the six pens is to generate an annual total yield of 6,000 tonnes (5,905 tons) – giving the site the highest output among the many fully submersible, deep-sea salmon farming sites throughout the country – while minimising costs.

Large capacity with easy deployability

The structure has all-steel construction, an LOA of 89 metres (292 feet), a beam of 45.5 metres (149.2 feet), and a height of 39.5 metres (129.5 feet), a displacement of approximately 1,800 tonnes (1,771 tons), and a total capacity of 60,000 cubic metres (2.11 million cubic feet). A rectangular design was chosen to eliminate the need for the diagonal brace structure typical of deep-sea fish pens.

The pen can be towed and repositioned as needed, and the truss structure is column-stabilised. This allows the fish pen to remain at specific coordinates for extended periods, which will in turn maximise the volume of harvested salmon during each offshore deployment.

The pen can submerge and lift itself out of the water with the aid of built-in systems, reducing reliance on specialised vessels. The pen is fixed in place via bottom-sitting ballast for improved stability. A floating control system can meanwhile ensure the structure can continue to operate under a range of sea and weather conditions, hence guaranteeing consistent output.

To permit harvesting operations for even longer periods, the pen was designed to allow maintenance and even repairs to be carried out on it even while out at sea. This eliminates the need for it to be towed to port for drydocking as part of both regular and unscheduled servicing.

Automation for greater efficiency

The other onboard facilities include those for feed storage, feed discharge, and intelligent monitoring of cage conditions. Also fitted are a liquid level telemetry system and an environmental monitoring system. The latter system combines the functions of a liquid level alarm, a feed feeding system, an energy supply system, and a system for monitoring hydrological parameters such as water temperature and dissolved oxygen in the sea area where the pen itself is deployed at any given time.

The onboard systems are automated to improve efficiency and to reduce the costs associated with manual feeding.

Construction of the new salmon pen was completed in compliance to China Classification Society rules. It is presently deployed some 10 nautical miles off the Rizhao Offshore Equipment Industrial Park in the city of Rizhao in Shandong province, where a salmon industrial innovation base was recently established complete with facilities for research and processing.