Evaluation of kelp harvest strategies: recovery of Lessonia berteroana (Phaeophyceae, Laminariales) in Pan de Azucar, Atacama, Chile

The brown alga, Lessonia berteroana, is the most exploited seaweed in South America, with majority of landings in northern Chile. We conducted population studies in a L. berteroana bed at the Pan de Azucar National Park in order to evaluate recovery potential under different harvest schemes. In an intact sub-population, L. berteroana size tendency varies with season, between median values of 150 cm in early spring and 40 cm in summer. Size is inversely correlated with density, which increases in summer due to a major recruitment phase (up to 40 ind m⁻²) and decreases in winter, with adult individuals (5 ind m⁻²) dominating. Size and recruitment showed a rapid increase in totally harvested areas and on artificial substrata. However, after summer harvesting, first recruits appeared after only one month in natural beds, while they needed up to five months on concrete blocks. Overall growth in wild populations was lowest, suggesting a strong dependence on density. Major thallus growth occurred in recruits from total harvest in autumn and from concrete blocks. We discuss these different recovery patterns and compare them with other commercial kelps in Chile, where similar approaches have been performed, expecting that they will help to improve Lessonia management in northern Chile.