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& Commercial aquaculture continues to expand as it strives to meet growing global demand for healthier protein. In this context, farmers are under great pressure to address problems of biofouling and predation, all while reducing operational costs and losses. Copper alloy mesh (CAM) has been shown to provide solutions to these problems, yet there has not been an in-depth study of economic benefits of adopting this new technology. This study was conducted in Chile using one 2010 grow-out cycle of trout (Oncorhynchus mykiss) and combined productivity indicators with economic analysis based on investment theory. Results showed that CAM net yielded better productivity indexes and higher net economic benefits than those of nylon net with anti-fouling coating. Sensitivity analyses showed a greater effect on the profitability of nylon versus CAM and a reduced elasticity of pen profitability with respect to the rental cost of CAM.

Deionized ammonium (NH3) acute toxicity (LC50-96h) in Patagonian blenny juveniles (Eleginops maclovinus) was assessed. Concentrations of deionized ammonium in salt water were prepared by using 24.09 ± 2.1 g ammonium chloride (NH4Cl). Fish were exposed in triplicates to different ammonium concentrations: 0.05; 0.094; 0.175; 0.325 and 0.605 mg NH3 L-1. Additionally, a control group was included. Experimental fish were kept at a photoperiod of 16:8h. Average temperatures were 16.24 ± 1.40 °C. Oxygen concentration was 7.16 ± 0.40 mg L -1. Water pH was 7.89 ± 0.2. LC50-96 h, was estimated by using Probit statistical method (95% intervals) using EPA software (1993). Juveniles of E. maclovinus showed a LC50-96h of 0.413mg NH3 L-1 value, different from most marine species. This study presents the first record of ammonium toxicity in marine species of Chile.

ABSTRACT. The increased activity of aquaculture in Chile involves cultivation of salmonids, oysters mussels and other species such, and to a lesser extent species such as red abalone (Haliotis rufescens) and Japanese abalone (Haliotis discus hannai). The aim of this study was to evaluate the growth rate of Haliotis rufescens and Haliotis discus hannai fed with different pellet based diets with Macrocystis sp. and Ulva sp., grown in ponds for 13 months. The results for both species denoted that there was an increase in length and biomass during experimental period, existing low growth rates during the austral winter (July-September) and increase during the austral summer (December-January). Results are consistent with descriptions of literature that there is high rate of growth during the summer and using diet of brown algae. From the economic standpoint abalone farming would be an economically viable activity for local aquaculture, considering the water quality and food requirements. Keywords: abalone, Haliotis rufescens, Haliotis discus hannai, growth rate, aquaculture. Tasas de crecimiento de Haliotis rufescens y Haliotis discus hannai en cultivos en estanques en el sur de Chile (41,5°S)RESUMEN. El incremento de las actividades de acuicultura en Chile involucra principalmente cultivo de salmónidos, ostiones, algas, mitílidos y otras especies, y en menor escala especies como los abalones rojo (Haliotis rufescens) y japonés (Haliotis discus hannai). El objetivo del presente estudio fue evaluar el crecimiento de Haliotis rufescens y Haliotis discus hannai alimentados con diferentes dietas a base de pellet Macrocystis sp. y Ulva sp., cultivados en estanques durante 13 meses. Los resultados para ambas especies denotaron que hubo incremento en longitud y biomasa durante el periodo experimental, existiendo bajas tasas de crecimiento durante invierno austral (julio-septiembre) e incremento durante el verano austral (diciembreenero). Los resultados concuerdan con las descripciones de la literatura en que hay altas tasas de crecimiento durante el verano usando dieta a base de algas pardas. Desde el punto de vista económico el cultivo de abalones sería una actividad económicamente viable para la acuicultura local, si se considera los requerimientos de calidad de agua y alimentación.