An alternative culture system for the hatchery production of abalone without using livefood

Stott’s Abalone Postlarval Production System (SAPPS) was developed to replace livefood as the primary means of settling and growing out abalone seed. Culture plates are initially sprayed with microalgal powder/agar gel solution to induce larval settlement. Abalone seed are then raised on an artificial diet/agar gel solution which is sprayed directly onto the culture plates. This study was conducted to test SAPPS on a commercial scale against the diatom biofilm method and two further trials were conducted to investigate the optimum feeding frequency and agar concentration for SAPPS. A total of 100,000 larval Haliotis diversicolor aquatilis were induced to settle onto 90 mucus conditioned commercial rearing plates (5 racks 18 plates each) in 1500-l tanks to test two treatments; diatom biofilm method and SAPPS. The trial was conducted over a 6-week period and the temperature averaged 24.2F 1.0 jC. Settlement was similar on all plates in the two treatments. The settlement rate per plate was 17,820F 8460 for the diatom biofilm and 17,280F 6390 for SAPPS. The postlarval growth rate on the SAPPS plates was over 50% higher than the growth rate on the diatom plates. The final length of postlarvae was significantly higher ( p < 0.05) on SAPPS plates (3281F 573 Am) than on diatom biofilm plates (2231F 314 Am). Furthermore, the survival of postlarvae was also five times higher on SAPPS (51.7%) compared with diatom biofilm (10.6%). SAPPS plates were heavily colonized by marine bacteria which may have acted as a food source for early postlarvae and assisted in the breakdown of polysaccharides. The whole body protein of juveniles was 17.2% in SAPPS compared to 13.3% in diatom biofilm which may suggest that artificial diet was a more balanced and complete nutrient source than diatom biofilm. Smaller scale trials were conducted over 25 days to determine optimum concentration of agar (2.5, 5.0, 7.5 and 10.0 mg/ml) and also to determine specific feed frequency (daily, every second day and every third day). There was no significant difference ( p>0.05) in survival rate in both trials. However, the 0044-8486/$ see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2004.03.008 * Corresponding author. Tel./fax: +81-354-630545. E-mail address: [email protected] (T. Takeuchi). A.E. Stott et al. / Aquaculture 236 (2004) 341–360 342 growth rate of postlarvae at 2.5 mg/ml agar was significantly lower than the other treatments and the leaching rate (% weight loss of food) was double that of agar concentrations 5.0–10.0 mg/ml. Growth rate was highest ( p < 0.05) in the feed frequency experiment for postlarvae fed daily and lowest for those fed every third day. The results suggested that agar concentration was optimal at between 5.0 and 10.0 mg/ml with plates being sprayed daily. SAPPS has potential to be used in industry depending on the development of a mechanized, cost-efficient system for spraying the plates. D 2004 Elsevier B.V. All rights reserved.