Fishery development: feeding in cage culture is not wasted, and underwater monitoring system can prevent fish from escaping.

The yellowfin tuna culture program carried out by the Water Test Institute has come to an end for the time being. Although it has yielded results, the operators are still waiting and watching. The reality is cruel, and what they are facing is the market problem, because the price of yellowfin tuna is not high enough. Before reversing consumers' impression of yellowfin tuna, the willingness of operators to cultivate yellowfin tuna is low. However, the four-year research plan has yielded results. The underwater residual bait monitoring system designed for the research can be applied to the cage-net culture management of other fish species, and the technology has been transferred to two aquaculture operators. This system will also be on display at this year's Taiwan International Fisheries Exhibition, which can help cage-net farmers monitor the status of food surplus and accurately control the amount of feed to save feed costs, as well as the health status of cultured organisms.

Wu Longjing, director of the Offshore Resources Research Center of the Aquatic Research Institute of the Council of Agriculture, said that in order to study the cultivation of yellowfin tuna, the marine cage net was rented from fishermen, and the kinds of food fed to yellowfin tuna were mackerel, mackerel, saury, etc., but it was impossible to determine how much bait could make the yellowfin tuna in the box net just enough to avoid wasting too much bait, so an underwater residual bait monitoring system was developed. Through this set of software and hardware equipment, 10% of the feed cost can be saved.

In fish culture, the proportion of feed cost is very heavy, about 50%. Therefore, if the feed cost can be reduced by 10%, it will be very helpful to the mariculturists. If the bait for cage culture is provided just right, it can also reduce the problem of environmental pollution in culture.

Wu Longjing said that if the marine cage culture is fed too much bait, it will create some problems after sinking into the sea. first of all, it will pollute the environment. Although it is cultured in the sea, it may still sink to the bottom because of the unfinished food in the cage net. The second is the problem of cost. Bait has always been the main cost burden of aquaculture fisheries. It is best to finish the feed so that money will not be wasted. Therefore, the more accurately you can control the demand for bait, the more you can improve the efficiency of breeding.

The underwater residual bait monitoring system developed by the Water Test Institute includes water surface and underwater image monitors, as well as software to transmit bait feeding and fish feeding directly to the ship and land offices through the network. Shore personnel can immediately grasp the situation of fish eating bait, and can adjust the amount of feeding. It is estimated that each box net can save 200000 yuan in bait expenditure every year.

The monitoring system also has side benefits, which can be used to observe the activity and health status of cultured organisms. At present, mariculturists have been used to monitor the cage net of sea fish, which can immediately find out whether the box net is damaged, avoid fish escape, and improve the overall efficiency of culture. Operators authorized by the Water Test Institute to use the underwater residual bait monitoring system can receive a royalty of 150000 yuan every two years. It will also be on display at the 2019 Taiwan International Fisheries Exhibition to be held in Kaohsiung in late September.

Picture from left to right: sea box net, water test station cultured in sea box net yellowfin tuna, underwater residual bait monitoring system real-time return image