Isolation of new
nanoplanktonic diatom strains and their evaluation as diets for juvenile
Pacific oysters (Crassostrea gigas)
R.M. Knuckey, M.R. Brown, S.M. Barrett, G.M.
Hallegraeff-2002
Aquaculture, 211(1-4): 253-274
Abstract:
Ten new diatom strains were isolated from coastal
waters of Australia and their potential as feed species for aquaculture
evaluated based on their cell size, division rate and biochemical
composition. All strains were within the size range ingested by most filter
feeders, i.e. 3-10 µm. Cellular growth rates of aerated 1.6-l cultures
ranged from 0.5-0.7 divisions·day-1 (Papiliocellulus simplex
CS-431, Nitzschia cf paleacea CS-433) to 1.7-2.0 divisions·day-1
(Attheya septentrionalis CS-425, Entomoneis cf punctulata
CS-426, Extubocellulus spinifera CS-428, Thalassiosira oceanica
CS-427). The latter four strains were also rich in energy storage fractions
(carbohydrate and/or lipid), especially as cultures progressed to stationary
phase.
Based on the initial screening, A. septentrionalis,
E. cf punctulata, E. spinifera and T. oceanica
were assessed as to their food value for juvenile Pacific oysters. The
diatoms were fed as part of a mixed diet-each making up 70-83% of the total
dry weight-together with an equal mixture of the haptophytes Pavlova
lutheri and Isochrysis sp. (T. ISO) over a 21-day experiment.
Diets containing A. septentrionalis and E. cf punctulata
were the most effective, producing growth rates (k=0.050 day-1)
marginally inferior to a similar (reference) diet containing a commonly used
aquaculture diatom strain of high nutritional value, T. pseudonana
CCMP 1335 (k=0.055 day-1). Regression analysis showed that
oyster growth rate was correlated with the content of protein in the equal
ration algal diets.
We have shown A. septentrionalis and E.
cf punctulata to be alternative Australian strains with good
nutritional value that could be utilised by oyster hatcheries or nurseries.
These strains, and others isolated in the study with different
characteristics such as benthic growth or high protein levels, could also
prove useful feed species for other animal species grown in aquaculture such
as abalone and scallops.