8/14/2019 Effect of Salt Addition and Feeding Frequency on Cascudo Preto Rhinelepis Aspera
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Short communication
Effect of salt addition and feeding frequency on cascudo preto Rhinelepis aspera(Pisces: Loricariidae) larviculture
By R. K. Luz1 and J. C. E. dos Santos2
1Laboratorio de Aquacultura da Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil; 2Estacao deHidrobiologia e Piscicultura de Tres Marias-CODEVASF, Tres Marias, Minas Gerais, Brazil
Introduction
The cascudo preto Rhinelepis aspera is a detritivorous fish
species that occurs in the Sao Francisco River (Sato et al.,
1998) and the Parana River (Agostinho et al., 1995). Thisneotropical freshwater fish is important for reservoir fisheries
and river ecology. It also has aquaculture potential, in
particular for the international ornamental aquarium industry.
However, little is known about effective larviculture of this
species.
Fish larval rearing is considered to be a difficult stage for
many species (Santos and Luz, 2009). Determining the best
feeding frequency is important to achieve better growth and
survival (Rabe and Brown, 2000), and to optimize laboratory
culture procedures (Luz and Portella, 2005). One potential
management option during larviculture can be the addition of
salt to the culture water for improvement in survival and or
growth of some freshwater neotropical species (Beux and
Zaniboni-Filho, 2007; Luz and Santos, 2008; Santos and Luz,
2009). Thus, rearing in different salinities during some days of
the culture then returning to freshwater at later stages is
important because the environment into which the juveniles
will be released for production or for stocking of reservoirs will
be freshwater.
The aim of this study was to evaluate the effect of low level
salt additions to the rearing water during the first 7 days of
exogenous feeding and, subsequently, determine the effect of
the return to freshwater for seven more days, using two
different feeding frequencies on growth and survival of
R. aspera.
Materials and methods
The experiment was conducted at the Hydrobiology and
Hatchery Station of Tres Marias, Minas Gerais, Brazil. Larvae
were reared under largely controlled conditions in 24 circular
aquaria (2-L volume; white color; constant aeration; photo-
period 10L:14D). The light level at the water surface was
150 lux. Each day at 09.00 h, temperature and dissolved
oxygen were determined in all aquaria using the YSI 55
equipment. Dissolved oxygen was 5.0 0.9 mg L)1 and the
average temperature was 26.0 0.8C. Artemia nauplii were
offered as food (daily prey concentrations = 400, 600 and
800 Artemia larvae)1, from 1 to 5, 6 to 10, and 11 to 14 days of
feeding, respectively). These levels were divided in accordance
to the feeding frequency. Aquaria were siphoned daily to
remove waste and about 50% total volume was renewed with
water from prepared stock solutions.
First-feeding larvae ofR. aspera (age 5 days; total length
= 6.23 0.32 mm; weight = 3.22 0.11 mg, n = 20) weretransferred directly from freshwater to various salinities:
S0 = freshwater (control); S2= 2 g salt L)1; S4 = 4 g
salt L)1; andS6= 6 g salt L)1. The larvae were reared under
these conditions during the first 7 days of feeding. For each
salinity, two feeding frequencies were used: F2= twice a day (at
08.00 and 17.00 h), and F4 = 4 times a day (at 08.00, 11.00,
14.00 and 17.00 h). Stocking density was 10 larvae L)1 (20 lar-
vae aquaria)1). The work was conducted with a 4 2 factorial
design (four salinities, two feeding frequencies, and three
replicates each).
The test media of freshwater and three salinities used in the
experiments were prepared and stocked in 500-L containers.
Commercial salt was used to prepare the solutions (Remo
Brazilian Industry). The pH values of the stock solutions were7.15, 7.19, 7.21 and 7.27, and the respective conductivity values
(lS cm)1) were 60, 3780, 6540, 9480 in freshwater, and 2, 4 and
6 g salt L)1, respectively (measured on the HORIBA U10
equipment).
After the first 7 days of feeding in different salinities and the
control, all larvae were counted to determine survival; samples
(n = 35) of larvae from each aquarium were fixed in formalin
10% to measure total length (mm) with an electronic caliper
(Starret), and individual weights (mg) to 0.0001 g precision.
To continue larval rearing, the larvae of all treatments were
transferred directly to freshwater and subsequently reared in
the freshwater for 7 days. For the transfer, fish were captured
with a 0.5 mm diameter mesh. After a complete waterexchange, fish were returned to the same aquaria. Due to
some mortality and larvae samples taken for measurement,
the stocking density was adjusted to reach 7 larvae L)1
(14 larvae aquaria)1). At the end, after 7 days in freshwater
(14 days of feeding), all animals were collected to determine
the survival and growth (weight and total length) as describe
above.
The specific growth rate (SGR) of larvae was determined
[SGR = 100 (lnWtf) ln Wti) Dt)1, with Dtthe time interval
(in days) between Wti (initial weight) and Wtf(final weight)].
Survival and growth data were compared by parametric
Factorial ANOVAANOVA, and means were compared using Tukey s test
at a 5% probability level using the SATISTICASATISTICA 7.0 program
(Statsoft INC., 2004).
J. Appl. Ichthyol. 26 (2010), 453455
Published 2010.
This article is a US Government work and is in the public domain in the USA.
ISSN 01758659
Received: November 1, 2008
Accepted: August 28, 2009
doi:10.1111/j.1439-0426.2009.01371.x
U.S. Copyright Clearance Centre Code Statement:01758659/2010/26030453$15.00/0
Applied IchthyologyJournal of
8/14/2019 Effect of Salt Addition and Feeding Frequency on Cascudo Preto Rhinelepis Aspera
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Results
Table 1 shows the growth and survival of R. aspera after
7 days of initial feeding at different salinity regimes and in
freshwater (control). Weight, SGR and survival were similar
among all treatments, without pronounced effects from salinity
(S), feeding frequency (F) or interaction between S F. Total
length, however, was significantly influenced by salinity
(P < 0.01) and feeding frequency (P < 0.05). The twice daily
feeding frequency showed better length growth than the four
times daily feeding regime, while rearing at a salinity of
6 g salt L)1 resulted in lower growth (as expressed by total
length) compared to the other salt treatments.Table 2 shows the growth and survival ofR. aspera reared
in freshwater after being returned from exposure to different
salt concentrations. Rearing for an additional 7 days resulted
in survival rates, weight, and SGR similar to control, and were
not significantly influenced by the initial exposure to various
salt concentrations (Si) or feeding frequency (F). There also
was no Si Finteraction effect. In contrast, total length was
significantly affected by the initial exposure to salt concentra-
tions. The worst effects (P < 0.05) were registered in speci-
mens exposed to the treatment S60.
Discussion
Five-day-oldR. aspera larvae can be transferred directly from
freshwater to water containing salt (up to 6 g salt L)1) and
reared under these conditions for the first 7 days of feeding.
After this period the animals can be returned to freshwater.
These osmotic changes do not affect survival. Low salinities,
up to 4 g salt L)1, have been demonstrated as allowing for
good survival when rearing freshwater larvae (Luz and
Portella, 2002; Beux and Zaniboni-Filho, 2007; Luz and
Santos, 2008; Santos and Luz, 2009). However, those studies
did not evaluate the effects of returning the test animals from
different salinities to freshwater. This tolerance to different
salinities during the larvae initial development suggests the
presence of mechanisms and structures related to the acclima-
tion process to osmotic variations. This is an important pointthat can be used in the prevention of diseases and to improve
juvenile production. The addition of salt (up to 4 g salt L)1)
can help reduce infestations in Rhamdia quelen ofIchthyoph-
thirius multifiliis (Garcia et al., 2007), a common parasite in
freshwater larviculture and which often causes high mortality.
Similar growth rates in freshwater and different salt
concentrations were verified in R. aspera larvae, except for
total length. This indicates that the species presents good
acclimation and tolerance capacity to salt concentration
exposures up to 6 g salt L)1. However, the reduced total
length registered in the fish reared at higher salinities is not well
understood. Future works need to elucidate fully the treatment
effects on the total length ofR. aspera larvae.
After transfer of the test specimens from the different saltconcentration exposures to freshwater, the weight gain and
Table 1Total length, weight, specific growthrate (SGR), and survival of Rhinelepisaspera larvae reared for first 7 days offeeding in different salt concentrationsand feeding frequencies
Total length (mm) Weight (mg) SGR (% mg day)1) Survival (%)
Means for Feeding Frequency (F)F2 13.4 1.4
a 33.6 4.5 33.5 2.0 88.7 7.4F4 12.6 1.2
b 27.7 8.3 30.3 4.4 85.9 11.5Means for Salinity (S)
S0 14.2 0.9a 31.9 6.9 35.5 3.2 92.5 9.3
S2 13.3 1.3a 30.8 8.4 31.8 4.4 86.6 10.8
S4 13.3 0.4
a
34.7 5.4 33.9 2.2 86.0 6.5S6 11.4 0.8b 26.5 6.5 29.8 4.0 84.2 10.7
Statistical F valuesFeeding frequency (F) 5.16* 3.91ns 4.44ns 0.13ns
Salt concentration (S) 10.82** 1.93ns 1.74ns 0.91ns
Interaction (F S) 1.16ns 1.86ns 1.37ns 0.20ns
Means followed by same superscript letters did not differ in Tukeys test (P < 0.05); *(P < 0.05);**(P < 0.01); ns(not significant). F2 = twice a day, and F4 = 4 times a day feeding frequency.S0 = freshwater; S2 = 2 g salt L
)1; S4 = 4 g salt L)1; and S6 = 6 g salt L
)1.
Table 2Total length, weight, specific growthrate (SGR), and survival of Rhinelepisaspera larvae during 7 days of feeding
in freshwater, after transfer from ini-tial rearing in different salt concentra-tions
Total length (mm) Weight (mg) SGR (% mg day)1) Survival (%)
Means for feeding frequency (F)
F2 21.1 1.0 121.7 14.9 18.4 2.5 97.0 7.1F4 20.9 0.7 117.6 20.4 20.0 4.4 95.2 10.1Means for initial salt concentrations (Si)
S00 21.8 0.5a 125.7 14.2 19.2 3.4 94.3 7.8
S20 21.4 0.7a 126.3 25.9 20.4 4.9 95.2 11.6
S40 20.5 0.4ab 119.0 9.9 17.6 2.6 95.7 9.6
S60 20.1 0.6b 107.6 5.8 18.9 2.3 100.0
Statistical F valuesFeeding frequency (F) 0.43ns 0.36ns 0.56ns 0.06ns
Initial saltconcentration (Si)
6.81* 1.04ns 0.59ns 0.50ns
Interaction (F Si) 0.32ns 0.11ns 0.85ns 0.66ns
Means followed by same superscript letters did not differ in Tukeys test (P < 0.05); *(P < 0.05);**(P < 0.01); ns(not significant).F2 = 2 times a day, and F4 = 4 times a day feeding frequency. S00,S20,S40, andS60initial salt concentrations used in first 7 days of feeding; final rearing in freshwater(more than 7 days of feeding).
454 R. K. Luz and J. C. E. dos Santos
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SGR in freshwater were similar to the controls, confirming
acclimation capacity to short-term osmotic changes. However,
the lower total length in the S60 treatment was simply a
consequence of the lower initial total length result from the
first 7 days of exposure to high salt concentrations.
The feeding frequency did not affect R. aspera larval
survival, weight gain or SGR during rearing in different salt
concentrations; however, total length was reduced when larvaewere offered food rations four times per day. After transfer
from different salinities to freshwater, the larvae can continue
being fed twice a day. Feeding frequency between twice and
four times a day also did not affected survival and growth of
Hoplias lacerdae (Luz and Portella, 2005), or walking catfish
Clarias macrocephalus(Petkam and Moodie, 2001) larvae. For
these species, twice daily feeding frequencies optimize labor for
other larviculture activities. However, feeding frequencies have
different results in different species (Cho et al., 2003; Kikuchi
et al., 2006; Mohseni et al., 2006). Different feeding frequen-
cies must still be tested for R. aspera juveniles and adults to
determine optimum management regimes for rearing.
Acknowledgements
This research received support from CODEVASF CEMIG,
Brazil and FAPEMIG (Fundacao de Amparo a` Pesquisa do
Estado de Minas Gerais, Brazil). We thank Dr Yoshimi Sato
for assistance and support during this work.
References
Agostinho, A. A.; Matsuura, Y.; Okada, E. K.; Nakatani, K., 1995:The catfish, Rhinelepis aspera (Teleostei: Loricariidae), in theGuara region of the Parana River: an example of populationestimation from catch-effort and tagging data when emigrationand immigration are high. Fish. Res. 23, 333344.
Beux, L. F.; Zaniboni-Filho, E., 2007: Survival and the growth ofpintado (Pseudoplatystoma corruscans) post-larvae on differentsalinities. Braz. Arch. Biol. Tech. 50, 821829.
Cho, S. H.; Lim, Y. S.; Lee, J. H.; Lee, J. K.; Park, S.; Lee, S. M., 2003:Effects of feeding rate and feeding frequency on survival, growthand body composition of Ayu post-larvae Plecoglossus altivelis.J. World Aquac. Soc. 34, 8591.
Garcia, L. O.; Becker, A. G.; Copatti, C. E.; Baldisserotto, B.; Neto,J. R., 2007: Salt in the food and water as a supportive therapy forIchthyophthirius multifiliis infestation on silver catfish, Rhamdiaquelen, fingerlings. J. World Aquac. Soc. 38, 111.
Kikuchi, K.; Nakahiro, I.; Kawabata, T.; Yanagawa, T., 2006: Effect
of feed frequency, water temperature, and stocking density on thegrowth of tiger puffer,Takifugu rubripes. J. World Aquac. Soc.37,1220.
Luz, R. K.; Portella, M. C., 2002: Trairao (Hoplias lacerdae)larviculture in slightly saline freshwater. Rev. Bras. Zootec. 31,829834.
Luz, R. K.; Portella, M. C., 2005: Feeding frequency throughouttrairao Hoplias lacerdae larval rearing. Rev. Bras. Zootec. 34,14421448.
Luz, R. K.; Santos, J. C. E., 2008: Stocking density and water salinityon pacama larviculture. Pesqui. Agropecu. Bras. 43, 903909.
Mohseni, M.; Pourkazemi, M.; Bahmani, M.; Falahatkar, B.; Pourali,H. R.; Salehpour, M., 2006: Effects of feeding rate and feedingfrequency on growth performance yearling great sturgeon, Husohuso. J. Appl. Ichthyol. 22(Suppl. 1), 278282.
Petkam, R.; Moodie, G. E. E., 2001: Food particle size, feedingfrequency, and the use of prepared food to culture larval walkingfish (Clarias macrocephalus). Aquaculture 194, 349362.
Rabe, J.; Brown, J. A., 2000: A pulse feeding strategy for rearing larvalfish: an experiment with yellowtail flounder. Aquaculture 191,289302.
Santos, J. C. E.; Luz, R. K., 2009: Effect of salinity and preyconcentrations on Pseudoplatystoma co rruscans, Prochilodus co-status and Lophiosilurus alexandrilarviculture. Aquaculture 28 7,324328.
Sato, Y.; Verani, N. F.; Verani, J. R.; Godinho, H. P.; Sampaio, E. V.,1998: Induced reproduction and reproductive characteristics ofRhinelepis aspera Agassiz, 1829 (Ostheichthyes: Siluriformes,Loricariidae). Braz. Arch. Biol. Tech. 43, 309314.
Statsoft INC., 2004: Statistica (data analysis software system). Version7.0.
Authors address: Jose C. E. dos Santos, Estacao de Hidrobiologiae Piscicultura de Tres Marias-CODEVASF, CEP.39205-000, Tres Marias, Minas Gerais, Brazil.E-mail: [email protected]
Management ofR. aspera larviculture 455