24 Sustainable Aquaculture
Marine fish farming in Japan Private and public alliances can help reduce the use of fishmeal and fish oil in feeds and mineral waste from feeds, as well as create awareness on antimicrobial resistance in fish farming By Renato E Kitagima
F
ish farming in Japan covers multiple freshwater, euryhaline and saltwater species due to diverse local demand for traditional Japanese cuisine. Many companies see opportunities in farming high-value species, rare species or promoting a specific characteristic of the product, including differentiated taste, special feed, clear brand concept or even fish size. Since Japan is an archipelago, food habits are strongly linked to ocean resources and consumption of a wide range of seafood is part of the general population’s regular basic diet.
fish in Japan is 280,000 tonnes annually (Figure 1). Of this, 73% is produced in the southwest of Japan (Shikoku and Kyushu regions), where higher water temperatures during spring, summer and autumn allow maximum fish growth. The north of Japan has lower water temperatures on average. However, many areas are not suitable for coldwater species like salmon due to the water temperature reaching over 20°C during high summer and the huge quantity of ocean ice blocks coming from the north during winter.
Globally, Japanese food is considered very healthy, and it is possible to find Japanese restaurants all over the world. In 2013, UNESCO nominated the traditional Japanese food “Washoku” as an “Intangible Cultural Heritage”. Appearance is crucial to Japanese cuisine, requiring a diverse variety of fish meat colours, textures, scents and flavours. Flesh quality is the main parameter when evaluating the value of the fish. Not only freshness or nutritional value but also smell, marbled meat appearance, correct processing and proper blood removal are important factors when selecting seafood in the market. On the other hand, it is possible for the main farmed species to see a commoditisation of prices because there is a certain standardisation on large-scale fish harvesting and processing.
Most of the production is based in net pens located close to the coast, mainly in bays. The main marine species (yellowtail, seabream and bluefin tuna) are usually farmed in net pens of 8–30m depth and up to 80m in width. The size and depth depend on the farming area and species. Smaller cages are usually used for tiger pufferfish or amberjack due to the need to regularly handle the fish for parasite management. Larger net pens are used in tuna farming, which has large harvests (30–100kg). There are many types of pen structures, including ones made from polyethylene, submersible net pens in areas that experience typhoons, and free-form net pens made from floats, ropes and net. However, the majority of net pens consist of a metal frame with revested styrofoam floats. Polymer-based nets are regularly used, while some farms use metal nets.
According to the Japanese Ministry of Agriculture, Forestry and Fisheries (MAFF 2018), the total production of farmed
Farmed fish production (tonnes)
Figure 1. Fish species production in Japan according to the Japanese Ministry of Agriculture, Forestry and Fisheries.
Figure 1 Fish species production in Japan according to the Japanese Ministry of Some 73% is produced in the southwest of Japan (Shikoku and Kyushu regions) where water temperatures are higher during spring, summer and autumn for maximum fish growth. Agriculture, Forestry and Fisheries. Some 73% is produced in the southwest of Japan July/August 2021 AQUA Culture Asia Pacific (Shikoku and Kyushu regions) where water temperatures are higher during spring,
