ENVIRONMENTAL VARIATION AND LARGE-SCALE GRACILARIA PRODUCTION

Temporal and spatial abiotic variation in seaweed farms should be anti cipated to maximize production through alternative exploitation strate gies. This study describes the basic assumptions and the most relevant data used to empirically develop a production model aimed at improvin g prediction and increasing production of Gracilaria farms in northern Chile. Continuous light and temperature recordings since 1986 have al lowed us to relate abiotic variations with high production seasons of Gracilaria or with the presence of pests and epiphytes. Much of the in terannual variations in light and temperature appear as part of a pred ictable pattern of change between ENSO (El Nino/Southern Oscillation) and inter-ENSO years. Production has been found to be a function of st ock density and harvesting frequency, two parameters that can be effec tively manipulated in the field. Thus, the range of climatic change no w can be anticipated to some extent which, in turn, suggests the best farming strategy. During seasons or growth periods anticipated to be h ighly productive, farming activities are oriented to maintain high per centage removal of the stock through frequent harvesting. During seaso ns anticipated to be low in production, activities are oriented to pre vent biomass losses due to the blooms of epiphytes and pests and to se cure stocks to renew through planting the damaged parts of the beds af ter the blooms.