Biology Reference
In-Depth Information
31.1
Introduction
White sturgeon (
Acipenser transmontanus
) is one of the most suitable
Acipenser
species for aquaculture production (Hochleithner and Gessner
2001
). White stur-
geon is reared for caviar production and for row and smoked fillets, whose market
has been continuously increasing over the years (Bronzi et al.
1999
). Feeding rate is
one of the most important factors influencing growth and feed efficiency of fishes
(Brett
1979
). Knowledge of the optimum feeding rate of a fish species is important
for the success of its aquaculture production, because it allows the farmers to obtain
the largest growth per unit feed cost, maintain good water quality, minimize
environmental stress, and, thus, maximize production efficiency. Several studies
have been conducted to determine the optimum feeding rates of white sturgeon
(Hung and Lutes
1987
; Hung et al.
1989
,
1995
, Deng et al.
2003
). There is,
however, no information on the optimum feeding rates of white sturgeon larvae
(2.2-15.8 g) from 6 to 10 weeks after initiation of feeding (Hung and Deng
2002
).
The objectives of the present study were to determine the optimum feeding rates
and to investigate the effects of feeding rates on the growth performances and
proximate body compositions of white sturgeon larvae at the 6th and 10th weeks
after initiation of feeding. This period of a sturgeon's life is particularly critical
because fishes overfed or underfed may be more susceptible to pathologies that
could contribute to the high mortality rates typical at this age.
31.2 Materials and Methods
One-day posthatch yolk-sac white sturgeon larvae (10,000) from a single progeny
were kept in two large, circular fiberglass tanks (150 cm diameter by 45 cm height
with 675 L water) that were supplied with 10-18 L/min per tank of degassed
groundwater with a constant temperature of 18-19
C. Larvae were fed a commer-
cial salmonid starter feed (Deng et al.
2003
) before the growth trials.
Two 1-week growth trials were conducted to determine the optimum feeding
rates of white sturgeon at weeks 6 and 10 after initiation of feeding that
corresponded to days 53-59 and 82-88 posthatch, respectively. At the beginning
of each trial, sturgeon larvae were captured randomly from the stock tanks and
distributed into 24 circular fiberglass tanks with 60 and 25 larvae per trial. Each
fiberglass tank (66 cm diameter by 15 cm water depth; 45 L water volume)
contained degassed groundwater supplied at 3 L/min per tank. Water temperatures
were measured twice daily. Two groups of 20 and 7 larvae, respectively, were
captured randomly from the stock tanks for determination of initial body weights
and initial body proximate compositions. The larvae were euthanized with an
overdose of tricaine methanesulfonate (1 g/L; Argent, Redmond, WA), blotted
dry, weighed as a group, placed in plastic bags, frozen in liquid nitrogen, and stored
