A sustainable culture system for Gracilaria parvispora (Rhodophyta) using sporelings, reef growout and floating cages in Hawaii

A culture system for the edible, red seaweed, Gracilaria parvispora Abbott (long ogo), was developed in Hawaii that utilized a hatchery to produce tetrasporophyte and gametophyte life stages of the seaweed, reef growout of sporelings to harvest size adults, and multiplication of the harvested thalli in floating cages prior to sale. A central cooperative operated the hatchery and floating cages, and marketed the product. Sporelings from the hatchery were distributed to coastal residents who established patches of seaweed on the reef and sold their harvest to the cooperative. Mean relative growth rate of seaweed in the cages over 52 weeks was 2.64% d^-1 and productivity was 14.8 g m^-2 d^-1 (dry weight), within the range of intensive culture systems. Cage cultures were not sensitive to water motion over the range of 4-14 cm s^-1 but growth and productivity tended to be higher in summer and spring than in winter. The culture system potentially overcomes problems that have hindered development of a sustainable supply of this species: low availability of wild stocks due to overharvesting; low productivity of spore cultures; and deterioration of vegetative cultures over time. Some of the elements may be applicable to other areas where wild stocks of Gracilaria have been overharvested.