An alternative culture
system for the hatchery production of abalone without using livefood
A.E. Stott, T. Takeuchi, Y. Koike-2004
Aquaculture, 236(1-4): 341-360
Abstract:
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 24.2±1.0 °C. Settlement
was similar on all plates in the two treatments. The settlement rate per
plate was 17,820±8460 for the diatom biofilm and 17,280±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 (3281±573 µm) than
on diatom biofilm plates (2231±314 µm). 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 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.
(Department of Aquatic Biosciences, Tokyo University
of Marine Science and Technology, Konan, Minato, Tokyo 108-8477, Japan,
e-mail of T. Takeuchi: take@s.kaiyodai.ac.jp)