Biological basis for the management of Gigartina skottsbergii (Gigartinales, Rhodophyta) in southern Chile

Environmental and biological parameters were analysed for populations of Gigartina skottsbergii (Setchell & Gardner) at Calbuco, Llanquihue Province (sheltered environment) and Ancud, Chiloe Province (exposed environment) in the south of Chile, with the aim of determining the biological basis useful in guiding management efforts for this species. In both populations, the biomass, density, recruitment, growth and survival showed maximum values in spring-summer. Most plants were sterile, and while cystocarps were present throughout the year, they were more abundant in autumn-winter. It was concluded that at Ancud, this species presents a synchronized and predictable population with high recruitment and low survival, while Calbuco showed low recruitment, higher survival and higher growth rates. Calbuco is, therefore, recommended as a growth (culture) area, and Ancud as an area for recruitment. As a management strategy, it is recommended that the harvest be mainly restricted to the end of spring (November-December), reducing towards the end of summer (February-March). Cutting should be selective and done by hand, removing fronds of at least 600 cm(2), corresponding to a frond length of a minimum of 25 cm.