5. General Culture Procedures
5.4 Mass Production on Algae and Yeast
Depending on the strategy and the quality of the algal blooms baker's yeast may be supplemented. The amount of yeast fed on a daily basis is about 1 g.million-1 of rotifers, although this figure varies depending on the rotifer type (S,L) and culture conditions. Since algae have a high nutritional value, an excellent buoyancy and do not pollute the water they are used as much as possible, not only as a rotifer food, but also as water conditioners and bacteriostatic agents.
In contrast to most European rearing systems, Japanese developed large culture systems of 10 to 200 metric tons. The initial stocking density is relatively high (80-200 rotifers.ml-1) and large amounts of rotifers (2-6 . 109 ) are produced daily with algae (4-40 m3 ) supplemented with yeast (1-6 kg).
The mass production on algae and yeast is performed in a batch or semi-continuous culture system. Several alterations to both systems have been developed but as an example the rearing models used in The Oceanic Institute in Hawaii are described:
• Batch culture system
The tanks (capacity of 1200 l) are half filled with algae at a density of 13-14 106 cells.ml-1 and inoculated with rotifers at a density of 100 individuals.ml-1. The salinity of the water is 23 ppt and the temperature maintained at 30°C. The first day active baker’s yeast is administered two times a day at a quantity of 0.25 g.million-1 of rotifers. The next day the tanks are completely filled with algae at the same algal density and 0.375 g.million-1 of baker’s yeast is added twice a day. The next day the rotifers are harvested and new tanks are inoculated (=two-day batch culture system).
• Semicontinuous culture
In this culture technique the rotifers are kept for five days in the same tank. During the first two days the culture volume is doubled each day to dilute the rotifer density in half. During the next following days, half the tank volume is harvested and refilled again to decrease the density by half. On the fifth day the tank is harvested and the procedure started all over again (=five-day semicontinuous culture system).
1.
Introduction
2. Morphology
3. Biology and Life History
4. Strain Differences
5. General Culture Procedures