Preparation and assessment
of microalgal concentrates as feeds for larval and juvenile Pacific oyster (Crassostrea
gigas)
M. Brown, R. Robert-2002
Aquaculture, 207(3-4): 289-309
Abstract:
We assessed a flocculation method for preparing
concentrates of seven microalgae. For five of these-Chaetoceros
calcitrans (C.CAL), C. calcitrans forma pumilum
[C.CAL(PUM)], Chaetoceros sp. ("tenuissimus-like")
(C.TEN), Skeletonema costatum (SKEL) and Isochrysis aff. galbana
(T.ISO) - we
assessed flocculates as an 80% diet component in four experiments with
larval and one with juvenile Pacific oysters. The remaining 20% diet
component was T.ISO, except in Experiment 2 for larvae, where C.CAL(PUM) was
used. The flocculates had been stored at 4 °C for 9-21 days and were
compared against the corresponding fresh microalgae.
For larvae (initial size, 74-82 µm), best growth was
usually seen in diets containing C.CAL(PUM). In Experiment 1, larvae fed an
80% C.CAL(PUM) (live) diet increased to 248 µm after 16 days. This growth
was >/= 50% more than with diets containing C.CAL(PUM) (concentrate) or
C.CAL (live or concentrate). In Experiment 2, larvae fed C.CAL(PUM) (live)
as the 20% basal ration (control) grew to 167 µm. Supplementation of this
diet with live or concentrated T.ISO as the 80% component did not improve
larval growth. In Experiment 3, larvae fed an 80% C.CAL(PUM) (concentrate)
diet grew as well as larvae fed the 80% C.CAL(PUM) (live) diet (192 and 194
µm, respectively) and more than larvae fed 80% C.TEN (live or concentrated;
155 and 162 µm, respectively). In Experiment 4, larvae fed 80% live SKEL
diet (125 µm) grew more than larvae fed SKEL (concentrate) or C.CAL (live
or concentrate) (larvae, 104-112 µm). Over all experiments, larval survival
ranged from 2% to 90% and was reflected in changes observed for larval
growth.
For juvenile oysters, a basal 20% T.ISO diet alone
gave moderate growth after 28 days (k=0.031/day). Supplementation
with a SKEL concentrate improved growth (k=0.054/day), whereas
supplements of live or concentrated forms of either C.CAL(PUM) or C.TEN gave
the best growth (k=0.083-0.090/day).
This study demonstrated that flocculated concentrates
of microalgae, especially C.CAL(PUM) or C.TEN, can be used effectively as
major dietary components for larval and juvenile oysters.