Growth and survival of juvenile red abalone fed with macroalgae enriched with a benthic diatom film

The objective of this work was to evaluate the growth rate of 150-day-old juvenile abalone Haliotis rufescens fed with blades of the seaweed Macrocystis pyrifera epiphyted with a film of the benthic diatom Navicula incerta. Five treatments were used as food for juvenile abalone: (1) blades of M. pyrifera washed for 10 min with fresh water to remove natural epiphytes; (2) blades of M. pyrifera without natural epiphytes and colonized with N. incerta at an initial density of approximately 500 cells mm super(-2); (3) blades of M. pyrifera with natural epiphytes; (4) blades of M. pyrifera with natural epiphytes and colonized with N. incerta; and (5) batch cultures of N. incerta without blades. All treatments were kept on 18-L plastic buckets with 10 L of "f/2" medium at 16 degree C and 100 mu Em super(-2)s super(-1) of continuous light. All treatments were kept under culture conditions for 2 days. Plastic buckets of 18 L filled with 10 L of filtered seawater at 16 degree C was used for the bioassay with the red abalone. The five feeding treatments were provided ad libitum to juvenile abalone and were removed after 4 days. The water exchange rate in the buckets was similar to 300% per day. Every 15 days, and for a period of 90 days, weight and growth (as shell length and width) were measured. At the end of the experiment mortality was determined. The results showed that the highest growth rates and weight were observed in treatments 2, 4, and 5 whereas the lowest growth rates and weight were observed in treatments 1 and 3. The highest average survival was recorded in treatment 5 (52.17%), whereas the lowest was observed in treatment 2 (34.20%). This study showed that the enrichment of seaweed blades improves growth and survival in abalone and thus has potential to be used in abalone farms to enhance productivity.