May/June 2010 - Global Aquaculture Alliance

Poultry feed 1
Shrimp feed 2
Molasses 3
Synthetic binder
Crude Protein
Fat
Fiber
Ash
Moisture
Table 1. Ingredient composition and proximate analysis
of experimental diet used for microbial floc culture.
Ingredient Content (g/kg)
both the RIC and MFC systems,
although molasses was not added to the
540.3
407.3
50.0
2.4
Proximate Analysis Content (g/kg)
1 147.3 g/kg crude protein, 37.1 g/kg fat, 61.1 g/kg fiber, 65.3 g/kg ash
2 368.9 g/kg, 55.0 g/kg fat, 28.0 g/kg fiber, 100.6 g/kg ash
3 53.4 g/kg, 0.4 g/kg fat, 1.8 g/kg fiber, 191.6 g/kg ash
235.2
425.0
43.8
98.8
79.9
Table 2. Performance of L. vannamei farmed at different densities
under microbial floc culture (MFC) or regular intensive culture (RIC).
Lowercase and capital superscripts indicate significant
differences among densities in each system (α = 0.05)
Performance
Variables System
Initial body weight (g)
Final body weight (g)
Weekly growth (g)
Final survival (%)
Final yield (g/m 2 )
50 Shrimp/
m 2
Shrimp Stocking Density
75 Shrimp/
m 2
100 Shrimp/
m 2
P
Value
RIC 3.99 ± 0.35 a 3.28 ± 0.22 b 3.58 ± 0.14 ab < 0.05
MFC 3.70 ± 0.36 A 3.26 ± 0.75 B 3.31 ± 0.25 B N.S.
RIC 21.22 ± 1.10 a 18.57 ± 1.26 b 17.27 ± 1.29 b < 0.05
MFC 20.22 ± 0.43 A 17.99 ± 1.67 B 16.95 ± 0.35 B < 0.05
RIC 1.68 ± 0.12 a 1.49 ± 0.11 ab 1.33 ± 0.12 c < 0.05
MFC 1.61 ± 0.04 A 1.33 ± 0.05 B 1.48 ± 0.16 B < 0.05
RIC 92.8 ± 7.6 a 72.7 ± 10.7 ab 67.2 ± 21.7 b < 0.05
MFC 81.6 ± 15.6 85.1 ± 10.4 80.0 ± 15.7 N.S.
RIC 771 ± 116 751 ± 158 766 ± 308 N.S.
MFC 629 ± 167 A 883 ± 152 AB 1.002 ± 225 B < 0.05
RIC tanks to control C:N rations in the
water. Tanks with 75 and 100 shrimp/m 2
With higher stocking densities, biofloc
production continued to increase until
shrimp harvest.
under MFC increased the amounts of
floc material in the water throughout the
culture period. However, a biofloc plateau
seemed to be reached at five to six weeks
of culture in tanks with 50 shrimp/m2 and in all stocking densities operating
under RIC conditions. Under MFC conditions
with 75 and 100 shrimp/m2 under MFC increased the amounts of
, biofloc
production continued to increase
until shrimp harvest.
Data collected in this study presented
strong evidence that the biological performance
of L. vannamei was not lost
when lower-protein diets were used
under intensive floc conditions. If these
results can be replicated within a commercial
culture setting, the method can
give a significant competitive advantage
to those operating or shifting to microbial
floc systems.
production
Bioreactor Technology For Tilapia
Advances In Latin America
The construction of V-shaped commercial bioreactors inside plastic tunnel greenhouses
began in 2000.
Summary:
Continued research and development
on tilapia culture is leading
to further advances in production
technology. Early biofloc-based
culture systems in tanks in Brazil
have given way to commercialscale
bioreactors housed in greenhouses
that utilize water fertilization
regimes, high-protein feeds
and salinity controls. Survival
and feed conversion have been
excellent, although growth rates
are less consistent than in more
traditional systems.
The first experiments with tilapia bioflocs
in subtropical southern Brazil were
conducted in September 1998 using procedures
similar to those the Oceanic
Institute concept of mesocosms, aquatic
controlled (MAC), applied to Litopenaeus
vannamei shrimp.
The first experimental units were 20
200-L plastic indoor tanks with aeration,
into which Oreochromis niloticus larvae
were stocked at densities of 1-10/L. An
objective was to overwinter them in commercial
units at low cost.
The survival and feed-conversion
ratios for fish at all densities were exceptionally
good compared to the performance
achieved using previously available
techniques. However, growth was low,
especially compared to shrimp produced
in similar bacteria-based systems in
Hawaii, USA, and Belize.
Greenhouse Bioreactors
The preliminary results motivated in
early 2000 the construction of commercial
1,000-m 3 V-shaped bioreactors inside two
800-m 2 plastic tunnel greenhouses. The
aim of the units was to overwinter 300,000
1-g tilapia fry purchased inexpensively at
the end of the growout season in late May
and sell large juveniles of up to 20 g at top
prices in September, just before the breeding
season.
The results of this first commercial
trial quickly changed when the fish grew
to the targeted 20-g size in the first 40
days, so it was impossible to sell them as
juveniles 90 days later. The fish were kept
growing with 25% of the forecasted feed
in order to check the carrying capacity of
the reactors and the growth curve up to
market size.
The fish attained commercial size in
150 days with an average feed-conversion
ratio of 0.77 and survival of 92%. However,
the size variation was very large, and
some fish grew 500 g in less than four
months. While external temperatures
averaged 5 to 10° C, water temperatures
inside the greenhouses were never below
28° C, and the floc was very stable and
always dark green.
The major changes to the MAC environment
in these initial floc trials was the
Sergio Zimmermann
Akvaforsk Genetics Center A.S.
N-6600 Sunndalsøra, Norway
sergio.zimmermann@afgc.no
higher water temperatures and the presence
of plankton influenced by the sunlight
in the greenhouse.
Expansion, Invention
By 2004, the project had 21 tilapia
bioreactors and 16 commercial growout
facilities in southern Brazil. One facility
in Colombia was dedicated to mesocosm
culture of first-feeding carnivorous larvae.
Several in Ecuador and Angola handled
nursery-phase tilapia juveniles.
Over the years, several protocols were
developed. A water fertilization regime
aimed at proper balancing of carbon,
nitrogen and phosphorus levels to favor
chlorophytes and avoid cyanophyte
blooms. High-protein feeds were used to
achieve excellent feed conversion. Salinity
controls that favor inland polyculture
with white shrimp were established to
improve the taste of both tilapia and
shrimp.
Recently, Storvik and Akvaforsk
Genetics Center A.S. tested the effects
of liquid oxygen at the FishSul facilities
with promising results. The commercialization
of tilapia culture in bioreactors is
becoming a marketing success, with no
diseases or water exchange reported over
the last 10 years.
Biofloc technology is an integral part of
the ongoing development.
30 May/June 2010 global aquaculture advocate global aquaculture advocate May/June 2010 31