Strain selection and initiation timing influence the cultivation period of Saccharina japonica and their impact on the abalone feed industry in Korea

Cultivations of the brown seaweed, Saccharina japonica, was developed, promoted, and industrialized in the 1970s and is highly valued in Korea both for human consumption and as a feed for the rapidly developing abalone farming industry. Production has continually increased, and approximately 442,637 tonnes wet weight was harvested in Korea in 2015. Abalone is a highly sought-after delicacy in Korea, and the abalone farming industry has been developed based on a stable production of seaweed. Korean abalone farmers prefer to feed their stock on locally cultured S. japonica; however, between August and November, the supply of farmed S. japonica declines because higher seawater temperatures reduce S. japonica productivity. In an attempt to overcome this temperature-induced period of low production, cultivation trials with a strain of S. japonica selected to withstand higher cultivation temperatures were undertaken. Strain selection involved using individual parent thalli that were found to remain productive under high seawater temperature (26 A degrees C) at Wando. Male and female gametophytes were isolated through 3 cycles of free-living gametophyte culture to produce the F-3 strain used in the production trials. Production trials using the selected strain were initiated every month between December 2014 and March 2015. This delayed the initiation of culture beyond the latest initiation time currently used by farmers (December). Delaying initiation of cultivation resulted in delayed maximum growth compared to the control. Growth of the F-3 strain continued for up to 3 months longer than normally achieved on farms for non-selected thalli. The mean length, growth rate, and biomass were also greater than those achieved by the control strain. The use of the F-3 strain of S. japonica coupled with delayed initiation of culture can therefore be used to help to ensure a stable year round algal feed supply for abalone industry in Korea.