This study was conducted to clarify the flow distribution behind a steel high-rise artificial reef. A 1/36 scale model was employed for the flume tank experiment, and the flow speed was set at 0.04 m/s in accordance with the Froude law, with a flow speed of 0.5 knots assumed under sea conditions. Seventy measurement points were set in one plane, and four planes were set at 0.11H, 0.35H, 0.74H, and 1.00H from the bottom. The flow speed range was measured from the rear end of the reef up to 7.0L for every 0.5L along the length, and 2.0W for every 0.5W along the width. The flow speed was measured using a three-dimensional electromagnetic velocity meter for 20 s, with a 0.01-s sampling interval. A deceleration zone with flow speed ratio of ≤0.9 was formed behind the fish reef in all planes. The deceleration zone with flow speed ratio of ≤0.5 was the longest at a height of 0.11H and was widely formed along the width. The deceleration zone formed behind the artificial reef was the largest near the bottom, where the structure was complex, and decreased in size as the height from the bottom increased.
The 2020 JSFE Symposium “Thinking about future aquaculture facilities” was held in December 2020. At the symposium, there were seven lectures on the current state and future prospects of aquaculture facilities, equipment that supports aquaculture, and aquaculture technologies. This paper is made of the seven lecture outlines that have summarized by symposium combiners.
Land-based aquaculture is one of the sea-food production systems in the specialized facility. This kind of aquaculture is located nearby human community. This aquaculture form has three kinds of water usage methods, i.e., running water system, closed recirculating system, and water pouring and recirculating system. These methods are used depending on the temperature, quantity, and quality of the supplied water. The functions that are intensive fish and shellfish production with high efficiency under artificial environmental condition, and accumulation of waste materials by recirculating aquaculture for environmental conservation are attracting a lot of attention in recent years. These functions can be used to enhance the growth of cultured fish and shellfish by controlling photoperiod, salinity of rearing water, etc. and to grow plants using the waste materials discharged from land-based aquaculture. In addition, there few location constraints and surplus energy, i.e., waste heat discharged from factories, hot spring heat, etc. can be used for aquaculture. Because of these characteristics, it can be integrated into human society and serve as a tool to bring about economic spillovers by collaborating other industries. This is expected to contribute to the development of aquaculture diversity.
The domestic and foreign trends of offshore aquaculture were reviewed based on the results of interviews and internet survey to overview its future directions. Regarding large-scale offshore aquaculture, there are two strategies; (1) the conventional aquaculture system that combines multiple cages and feeding platforms is enlarged and expanded, and (2) a super-large aquaculture system with a production capacity of 10,000 tons per year is newly developed. In addition, semi-closed or closed Recirculating Aquaculture Systems (RAS) on the sea is becoming conspicuous. On the other hand, regulatory uncertainty such as a permitting issue to use sea area has been identified as one of the main barriers to offshore aquaculture development. Technological development and systemization are also required to promote offshore aquaculture. Prospects include collaboration between offshore aquaculture and renewable energy industries such as offshore wind power generation. Including the permitting issue, Marine Spatial Planning (MSP) is expected to utilize the marine space in versatile and effective way. From a view of aquaculture in harmony with the surrounding environment, Integrated Multi Trophic Aquaculture (IMTA) is one of the promising measures for offshore aquaculture as well as for aquaculture in protected seas. It will be difficult to secure the feed if the offshore aquaculture develops rapidly. Several researchers are interested in enhancing marine productivity and producing fish oil and meal using deep sea water with rich nutrients upwelled by renewable energy.
In order to demonstrate an ICT-based aquaculture in a fishing port, the monitoring and conservation systems for the aquaculture environment, remote feeding system and power supply system using renewable energy were constructed, and horse mackerel were culture.
As a result of the demonstration tests conducted for more than two years, each system generally operated as intended. The seawater temperature and DO could be monitored by mobile phones/PC, and when the water temperature exceeded 25°C or the DO values were less than 4 mg/L, alarm e-mails were sent to the person in chage. The air pump was pumped 10 liters air per minute to the aquaculture net when the low DO values were measured. The remote feeding system was seemed to encourage newcomers to aquaculture because fishermen could feed culture fish even when they were operating offshore. In addition, the amount of fish fed had reduced compared to manual feeding with remote feeding. Therefore, we considered that the introduction of ICT-based aquaculture systems would contribute to the prevention of seawater quality by catching of culture fish before they die and reduction of leftover feed.
Because there was no grid power at the test site, renewable energy was used as an electrical power source. As a result, even in the northern Japan region such as the test site, the electricity required for ICT-based aquaculture systems could cover by photovoltaic power generation. Furthermore, we found that equipment costs can be reduced by using the southern exposure parapet of the breakwater as a mount base for PV panels.
In the aquaculture industry, efficiency and smart aquaculture utilizing various technologies are progressing from a labor-intensive business format. Challenges in the aquaculture industry include reducing production costs and risks and increasing added value in terms of sales and distribution. In response to these issues, the demand for monitoring that utilizes various technologies are increasing. In this paper, we will introduce the development and social implementation of monitoring technology that Umitron has been working on and illustrate examples of data utilization.
As the action strategy planned by prefecture office to boost the exporting of yellow tail products, the academic-industrial cooperation project has facilitated the ICT systems on seafood fish aquacultures farm in Kagoshima prefecture. The purpose of the ICT facilitating is to sophisticate the system of production control, which is expected to improve the workload such as manual work using pens and record papers, re-typing the data on PC after working on the farm and data sorting to think better operation control. In Japan, aquaculture operators have not put attention digital recording system because the control skill knowhows have been in operator brain as his and her tacit knowledge, but the ICT will take an opportunity to change the laborious manual work, and to start data analysis for improving the management controls. Seafood market will continue grow world widely, from the sight of prepare for being high level business operation, digital data system will be more important to introduce scientific business approaches to improve the management control.
Sensor technology is one of the critical enablers of the trend that the demand for sustainability and quality of life triggered new players’ involvement in its value chain. Digitalization connected industries and a vast number of people. The digital transformation wave impacts fisheries and aquaculture without exception in exchanged practices and resources across borders and industries. The new technology trend of sensors on the aquaculture monitoring system will make sensors more accurate, massive sensing points, more intelligent. The stakeholders will be easy to be connected due to digitalization. It will give us some new perspectives on running the fishery and aquaculture business, not only for better productivities.