Final yield of the brown alga Cladosiphon okamuranus (Chordariaceae, Phaeophyceae) may depend on nursery quality

SUMMARY Cladosiphon okamuranus (Chordariaceae, Phaeophyceae) production is an important economic activity in the islands of Okinawa, Japan, and has been unstable for the past decade. Local producers surmise that unstable yields are related to highly localized environmental conditions. We report that the differential yields of C. okamuranus harvested from experimental nets during the 2019 season at two adjacent nurseries (less than 40 m apart), which were designated as a poor or good nursery by local producers, were 137 and 253 kg (wet weight), respectively. In fact, nutrient conditions between the poor and good nursery were slightly different, although involvement of some unsurveyed environmental factors cannot be excluded at present. Additionally, we report on a thallus shearing phenomenon that led to the catastrophic loss of thalli from the cultivation nets.