P.G White.
Abstract:
Rotifer culture at commercial marine fish hatcheries in the
Mediterranean region relies on the culture and feeding of algae and
dry baker's yeast. Trials were undertaken to evaluate methods for the
mass culture of rotifers without algae, using two commercially
available artificial diets, Culture Selco (INVE Aquaculture NY
Belgium) and Rich (Sanders, USA) plus dry yeast were compared for
the culture of two different strains of rotifer, large L - type originating
from CCAP, Scotland and small S - type originating from Kagoshima,
Japan) in plastic sacks on a commercial scale. Comparisons were also
made of the sources of rotifer inoculum and relative costs.
The culture facilities comprised of 14 cylindrical plastic sacks (800
liter capacity) held in plastic coated wire mesh frames. Rotifers were
inoculated at 150 - 250 rotifers/ml and batch cultured at 23 - 25 C for
6 days. Rotifers were fed 4 times daily with freshly prepared feed.
Rotifers were harvested into a 40 micron mesh and then enriched
further with algae or Sanders Rich (100 ppm at 25 C ) before feeding
to seabass or seabream larvae.
The first trial compared the two artificial diets on the culture of two
different strains of rotifers. For both large and small rotifer strains,
production was higher when fed Rich and yeast, 4.2 % and 8 %
respectively. With both diets, the L - type rotifers reproduced 9.3 %
faster than the smaller S - type rotifers.
The second trial compared the source of rotifers used as inoculum by
comparing rotifers previously grown on yeast and algae to rotifers
previously fed artificial diets. Rotifer production was higher by 11.2
% when rotifer inoculum was previously fed with a combination of
Algae and yeast.
The cultures was assessed for contamination with ciliates and
flagellates and for collapse for each artificial diet and each rotifer
strain. The rotifers fed Rich and yeast were more prone to
contamination (16 %) compared to Culture Selco (8 %), but there was
no significant difference in occurrence of culture collapse. The
existing technique using algae and yeast experiences 26 %
contamination and 2 % collapse, but feeding with either of the
artificial diets tested gave improved culture stability.
The cost of rotifer production was determined for each diet. The
quantity required per million rotifers produced was 2.61 grams of
Culture Selco or 2.1 grams of Rich plus yeast. The feed cost of rotifer
production was ten times less when using the combination of Rich
plus yeast.
Conclusion: the optimum rotifer productivity was achieved by using
L - type rotifers fed on Rich and yeast from inoculum previously fed
algae and yeast.
(Ithaka Fisheries SA, Makria Pounta, Ithaca 28300, Greece)