Large-scale hatchery of the kelp Saccharina japonica: a case study experience at Lvshun in northern China
The giant kelp farming industry in China, with an annual production of 1.4 million t (dry weight, DW) in a farming area of 130,564 ha, depends on a safe and constant supply of sporelings each year that are nurtured in ca. 20 commercial hatchery enterprises in Shandong and Fujian provinces in the north and south, respectively. Extension of the kelp growing period in the sea relies on the use of the so-called summer sporeling. Its production is based on using recirculated cold water (5–10 °C) to allow gametogenesis to happen and thereafter the young sporophytes to grow in summer when the ambient seawater temperature (above 20 °C) is too high. This allows sporophytic sporelings to be transferred to open water in early autumn, 2 months earlier than naturally occurring plants in coastal populations. Although historically commercially viable and successful, there have been few reports to describe this hatchery process. In this case study, the entire process of a commercial hatchery manipulation in the 2015 production season at Lvshun, Dalian, northern China, is presented, including pre-treatment of parental plants, control of spore release, and control and adjustment of solar irradiance and temperature at different developmental stages of the plants as well as the nutrient supply regime over the entire course. Analyses of the data and process in this report is expected to shed light on future optimization of the technique as well as providing useful clues for other farmed kelp species in other regions of the world.