Clément, A., Aguilera, A., Canello, F., Grünewald, A and X. Rojas (*); Plancton Andino Ltda (PAL), P. O. Box 823, Puerto Montt, Chile, Phone: + 56 65 23 5046; Fax: + 56 65 23 5663; (*) Intesal, S.A. Luis Ross 548. Puerto Montt, Chile. http://www.plancton.cl/

Abstract

• Long term phytoplankton monitoring program is a practical tool to decrease risk of HAB and generates useful information and adequate management. Main results can define critical period, vulnerable areas, as well as inter-annual variability risk associated with meteorological -oceanographic anomalies. In addition, the results can be applied to improve the mitigation techniques, particularly those used in fish farms.

• Harmful Algae Bloom (HAB) caused by Leptocylindrus spp., Ch. convolutus, Heterosigma, Dinoflagellates, etc. present different seasonal and spatial pattern. Their impact depends on the functional group of algae and specie, site conditions, and type of animal in culture. Dinoflagellates are more often in summer and early fall, and generate greater impact, however, they have a low frequency appearance. Diatoms are more recurrent in spring, winter and early summer, but with a major frequency and this functional group created lower impact. Positive and negative rainfall anomalies have an influence in the frequency and harmful algae species. Most of the events (HAB) occur during negative anomalies, i.e., years with lower rainfall than normal.

• During the time period of analysis, ca. a decade, in general and using an annual basis statistic, the major numbers of events (HAB) per year are directly proportional to the highest negative anomalies observed. The majority of HAB due to flagellates (dinoflagellates and Heterosigma) occur during negative anomalies.

• From a practical point of view, oceanographic events and meteorological times series are an important tools to forecast the potential conditions for HAB in the South inland sea of Chile.

• However, the most relevant procedure for the aquaculture industry is the "action" or mitigation techniques to avoid the risk. Therefore, fish farmers are using different site-specific technology to protect the fish biomass, rather than killing or removing the harmful algae from the water.