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International Journal of Aquaculture, 2013, Vol.3, No.25, 147
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151
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149
Figure 1 Growth of pirarucu fed at rates of 2.0% or 3.0% body
weight/day in 4 m
3
cages and cultured for 210 days. Data are
means±SD of two replicate cages in Pereira de Miranda
Reservoir (Ceará State, Brazil)
growth of pirarucu was not influenced with increasing
feeding rate. Therefore, the data obtained suggest that
feeding rate of 2.0% body weight/day could be near
the level of satiation of 1550 g pirarucu juveniles.
However, various authors reported report similar
results about growth of pirarucu. Bard and Imbiriba
(1986) reported pirarucu in ponds reached weights
ranging from 4037 to 4497 g in only 152 days when
stocked at an initial weight of 126 to 388 g. According
to Pereira-Filho et al. (2003), this species cultured
under intensive production system in ponds reached a
maximum weight of 7000±1100 g after 365 days.
Similar stocking densities and production rates have
been reported for the cage culture of other carnivorous
fishes: 14.5 to 34 kg/m
3
for Atlantic salmon (
Salmo
salar
) in 120–2000-m
3
cages (Turnbull et al., 2005;
Oppedal et al., 2011), 42.0 kg/m
3
for spotted wolffish
(
Anarhichas minor
) in 100-m
3
cages (Mortensen et al.,
2007) and 35.0–61.2 kg/m
3
for rainbow trout
(
Oncorhynchus mykiss
) in 1.0-m
3
cages (Wallat et al.,
2004). However, Ono et al. (2004) reported
production rates varying from 80 to 140 kg/m
3
for
pirarucu in 15–300-m
3
cages. Growth has been
reported to increase with feeding rate in several fish
species (Eroldogan et al., 2004; Yuan et al., 2010; De
Riu et al., 2012; Okorie et al., 2013). Under a
condition of low feeding rate, fish tend to optimize
their digestion to extract more nutrients more
efficiently, thus decreasing the FCR (Puvanendran et
al., 2003; Van Ham et al., 2003). In the study, only the
FCR was significantly affected by feeding rate.
Apparently, the experiment indicates that the rate of
2.0% body weight/day could be around satiation. As
several authors have indicated optimum feeding rates
in fish to be below satiation (Kim et al., 2007; Okorie
et al., 2013), the rate of 3.0% body weight/day in
1,500–7,000 g pirarucu appear to be actually higher
than values for this size range in this species. The
mean FCR of pirarucu cultured increased with
increasing feeding rate. FCRs of fish in the groups fed
at 2% and 3% body weight/day were higher than the
FCRs determined for other studies. Pereira-Filho et al.
(2003), Crescencio et al. (2005) and Oliveira et al.
(2012) reported FCR of 1.2 to 1.9 to pirarucu
juveniles. However, similar observations have been
reported for other fish cultured in cages. Mazzola et al.
(2000) reported FCR of 3.5 to Mediterranean
amberjack,
S. dumerili
, fed with pellets diet. The FCR
of grouper,
Epinephelus coiodes
, cultured in ponds
and fed with pellets diet was 3.2 (Bombeo-Tuburan et
al., 2001).
3 Conclusions
This study has shown that pirarucu can be efficiently
grown to market-size in cages and its growth is much
faster than other fish species that have the advantage
of decades of research and genetic improvement. The
data obtained suggest that pirarucu fed at 2% body
weight/day show better zootechnical indices. However,
the optimal feeding rates have not been identified and
further research is necessary using several culture
phases (0.1~1 kg; 1~2 kg; 2~5 kg; 5~10 kg) and
feeding rates various (1, 1.5, 2, 2.5 and 3.0% body
weight/day).
4 Materials and Methods
Seven-months-old pirarucu juveniles (1550.0±85.6 g;
59.2±5.5 cm; mean±SD) were obtained from
Aquaculture Research Center of National Department
of Works Against Droughts (DNOCS; Pentecoste,
Ceará, Brazil) and
were transported to Pereira de
Miranda Reservoir (Pentecoste, Ceará, Brazil). Pereira
de Miranda Reservoir has a surface area of 5486 ha, a
volume of 395,000,000 m
3
and an average depth of
7.2 m with a maximum depth of 22 m. Open fishery