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The Journal of NOAMI, 36(1-2): 131-144 (June & December 2019)
EVALUATION OF HUFA ENRICHED ARTEMIA NAUPLII FOR
THE GROWTH, METAMORPHOSIS AND SURVIVAL OF
MACROBRACHIUM ROSENBERGII LARVAE
Md. Abdul Kaiyum1, Hossain Zamal2 and Md. Sohel Parvez3*
ABSTRACT
The experiment was conducted to study the evaluation of Highly Unsaturated Fatty Acids
(HUFA) enriched Artemia nauplii for the growth, metamorphosis and survival of
Macrobrachium rosenbergii larvae. The larvae were fed with Artemia nauplii (live feed)
enriched by HUFA emulsion at the rate of 0.5 ml and custard. It was revealed that HUFA
enriched Artemia increases the growth and survival rate and minimizes larval rearing
period of M. rosenbergii. Growth performance of larvae fed on HUFA enriched Artemia
nauplii in T-4 showed better performance than the others. The higher daily mean growth
rate, specific growth rate and survival rate was found in treatment-4. PL was observed at
35th day, 29th day, 28th day and 26th day in T-1, T-2, T-3 and T-4, respectively, lower
larval rearing period indicates lower cost of production in T-4. FCR was found 2.11,
1.91, 1.75 and 1.48 in T-1, T-2, T-3 and T-4, respectively which was an excellent out put
of lower FCR in T-4 (1.48) that is the indicator of better food utilization. The stress test
of the PL of T-4 (95%), T-3 (92%) and T-2 (80%) indicate the better quality fry
production in three treatments.
Keywords: Giant freshwater prawn, Hatchery, Larviculture, Lipid enrichment.
INTRODUCTION
The successful larviculture of Macrobrachium rosenbergii in the hatchery is significant to
support prawn farming ventures worldwide that requires adequate supply of good quality
food (Aviz et al., 2018; Valenti et al., 2010; Dhont et al., 2010). Different live foods are
widely used and requirement of such food act as a limiting factor in the larviculture of
different commercially important species (Kovalenko et al., 2002). The brine shrimp,
Artemia sp. has proven the best and principal live food among all live foods and artificial
diets in rearing larval crustaceans of commercial value specially M. rosenbergii and many
other species. (Barros and Valenti, 2003; Thuy and Chavalli, 2000).
However, there are some shortcomings in the use of live food, like variable nutritional quality
and availability, risk of introduction of exotic organisms and pathogens into the culture
system, and the high costs (Kovalenko et al., 2002). The important issue to be considered is
that the content of different essential fatty acids is not enough to satisfy the requirements of
* Corresponding author email: sohel@nstu.edu.bd
1 Institute of Marine Sciences and Fisheries, University of Chittagong, Bangladesh.
2 Department of Fisheries, University of Chittagong, Bangladesh.
3 Department of Oceanography, Noakhali Science and Technology University, Bangladesh
132 Parvez et al.
the larvae (Thuy and Chavalli, 2000). Whereas, the HUFA is very essential in the larval
stages of freshwater prawn, M. rosenbergii (Devresse et al., 1990). The nutritional quality of
Artemia nauplii is need to be improved by the enrichment with highly unsaturated fatty acids
and other nutrients before use. This study was designed to evaluate the different HUFA
enriched Artemia as food in the larval rearing of M. rosenbergii at hatchery control
environment.
MATERIALS AND METHODS
Experimental Design
The research was conducted in a hatchery (AG Aqua Hatchery) of the village Darbeshkata
under Poshchim Borobhewla Union in Chakaria upazilla under Cox’s Bazar district. It is one
of the biggest Macrobrachium hatcheries in Bangladesh.
Larval rearing tank preparation
Eight tanks with 250 liter capacity were prepared as larval rearing tank (LRT). There were
four treatments and each treatment had two replicates. In larval rearing cycles all the
equipments and tanks were scrubbed and treated with 50 ppm formalin, or 50 ppm calcium
hypochlorite or 4ppm KMnO4 for one day. They were then flushed and dried in sunlight for a
few days, then rinsed and flushed before reusing. After cleaning with fresh water all the
material were introduced for detergent wash and finally flashed with fresh water. Then bleach
was done to remove the microorganisms. After bleach wash acid wash was done to confirm
more hygienic condition using HCI. After 24 hours all materials were well flashed with fresh
water and were kept for drying. Finally the tanks and air–stone were kept in 200 ppm
formalin for an hour.
Water Treatment
Water was treated before use in the hatchery through some form of physical (gravel/sand
bed) filter. Aeration was performed with a compressor, consists of two oil-free air blowers of
10 H.P. with P.V.C. air grid. Each of the hatchery units was connected with an air pipe to
provide aeration. A temporary pipe line was extended to provide aeration in the drums used
for this study. The tanks were aerated by air stones. For destruction of microorganisms from
the larvae, they were disinfected with 25ppm formalin for 30 minutes, and also with vigorous
aeration. They were acclimated to water salinity 12ppt in three hours.
Stocking Larvae in LRT
The stocking density of prawn larvae in larval rearing tank was 100 ind/L. The hatched
larvae were collected in 10liter bowl and strongly aeration was done. A 10 ml pipette was
used for counting from five corner of the bowl and make an average. By this method total
hatched larvae were stocked in the larval rearing tanks. In four Treatments of eight
tanks/drums no T-1a, T-1b, T-2a, T-2b, T-3a, T-3b, T-4a and T-4b, and each of the tanks were
stocked with 100 ind/L.
Evaluation of Hufa Enriched Artemia Nauplii for the Growth, Metamorphosis 133
Enrichment of Artemia Nauplii
In this research HUFA emulsion has been used because HUFA enrich provides all the
essential fatty acids of the marine ω-3 HUFA type. It is especially high in the important fatty
acids DHA and EPA. Use this emulsifying concentrate to increase the highly unsaturated
fatty acid content in Artemia use for larvae as live feed in hatchery operation of prawn. The
HUFA emulsion suspension was used at a concentration of about 0.5ml per liter of seawater.
The mixture was aerated for at least 10 minutes to ensure good mixing before adding hatched
Artemia nauplii. The nauplii with the enrichment medium were incubated at a density of 350-
400 nauplii/ ml. Three jars/containers were used for three equal time interval enrichment
experiment. After 3, 6 and 12 hours, samples were taken from every enrichment medium at
every time interval for observation. Under microscope small particles into the gut indicated
the food taking for enrichment by HUFA emulsion.
Figure 1: Flow Chart of Enrichment of Live Feed (Artemia nauplii)
Dose of HUFA emulsion depend on the amount of live feed Artemia nauplii. It should be
need 4-5 nauplii/ml in hatchery operation of prawn larvae and in 250 liters tanks where
stocking larvae was 100/L need 12,50,000 nauplii.
Newly Hatched
Nauplii
Enrichment
Non-enriched
(Control)
3 hours
Enriched
6 hours
Enriched
12 hours
Enriched
T-1a
T-1b
T-2a
T-2b
T-3a
T-3b
T-4a
T-4b
Treatment-1
Treatment-3
Treatment-4
Treatment-2
134 Parvez et al.
Table 1: Dose of HUFA Emulsion
Treatment
Time duration
Feed
Dose of feed
(ml/L)
T-1
Newly hatched
Without feed
-
T-2
After 3 hrs of enrichment
HUFA emulsion
0.5
T-3
After 6 hrs of enrichment
HUFA emulsion
0.5
T-4
After 12 hrs of enrichment
HUFA emulsion
0.5
Treatment Groups
There were 4 treatments used in the present experiment. The group which fed on non-
enriched Artemia was identified as T-1. The group which fed on 3 hours enriched Artemia
was identified as T-2 and fed on 6 hours & 12hours enriched Artemia was identified as T-3
& T-4.
Feeding
No feed was given for the first day. From the2nd to 10th day T-1was fed on and T-2, T-3, T-
4 was fed on 3hrs, 6hrs & 12hrs enriched Artemia was used as live feed.
Maxima
Enriched / non-
enriched
Artemia
Flack
No Feeding
Artemia
Custard
1 2 10 13 11 12 25 26 27 28 29 30 31 32 33 34
Figure 2: Feeding Regime of Fresh Prawn Larvae
From 10th day to PL stages treatment-1 was fed on non-enriched Artemia nauplii and same
types of enriched (3hrs, 6hrs & 12hrs) Artemia nauplii with formulated feed was applied in
LRT. Feeding ration size was adjusted on the basis of feed by the larvae. Feeding trial was
started after first day. Every stage feeding ration size was readjusted on the basis of
survivability of larvae. Feeding ration size was increased with the increase of larval
development and maintained equal ration size for all (four) treatments. On the other hand,
enrichment of Artemia nauplii completed before feeding schedule.
Evaluation of Hufa Enriched Artemia Nauplii for the Growth, Metamorphosis 135
Table 2: Dose of the Feed Used in Larval Rearing
Feed
Time
Dose
Artemia
8am & 6pm
20g/ton
Maxima
7am, 10am, 3pm & 10pm
20g/ton
Custard
5am, 9am, 11am & 1pm
50g/ton
Artemia flack
5am & 9pm
1.5g/ton
Water Quality Maintenance
The air supply was turn off to allow solid particle to settle and siphon of surplus food
particles and metabolic wastes from the bottom of the tank. After ten to fifteen minutes, the
uneaten food, wastes and death larvae at the middle of the tank bottom removed by
siphoning. This task has been done daily afternoon. The rates of water exchange depend on
the water quality and the larval development rate. Water exchange was done 20-30% volume
of everyday. The quantity of water exchange may even be increased to over 50% per day
toward end of the rearing cycle, when biomass and feeding level are at their greatest.
Medication
On the day of stocking EDTA 6ppm for unlimited time.
On 3rd day of stocking OTC 4ppm for 24 hours (25% water exchanged).
On 7th day of stocking Formalin 25ppm for 24 hours (30% water exchanged).
On 10th day of stocking OTC 4.25ppm for 24 hours (30-40% water exchanged)
On 14th day of stocking Formalin 25ppm for 24 hours (30% water exchanged)
On 20th day of stocking Erythromycin 0.75ppm for 24 hours
On 21st day of stocking Formalin 25ppm for 24 hours (30% water exchanged)
On 25th day of stocking OTC 4.5ppm for 24 hours & Multivitamin 0.25ppm.
On 28th day of stocking Formalin 25ppm for 24 hours (30% water exchanged)
On 32nd day of stocking OTC 4.75ppm 24 hours & Multivitamin 0.5ppm.
On 35th day of stocking Erythromycin 0.8ppm for 24 hours.
Sampling
Design of sampling consisting of four treatments and each treatment has two replicates.
Biological parameters were sample every day. Stage base was done for length and weight
measurement of the larvae. Firstly, larvae were randomly sample from LRT by PVC pipe.
Then they were placed into an aerated beaker of water. An electronic balance with up to
0.000001g denomination and 1 mm scale up to a centimeter graduation were used for length
and weight measurement, respectively. Physico-chemical parameters were monitored every
day. As there was no significance difference of the water parameters for every day, so the
averages of the values of three days were recorded for each treatment. The sample larvae
were handling carefully to avoid handling stress.
136 Parvez et al.
Determination of Increment of Length and Weight
Feeding trial was started from 2nd days and lasted 28th days. So the increment of weight was
recorded after the 1st days and continued for PL stage. For measuring weight, 30 larvae (15
for each LRT) were sampled for treatment 1, 2, 3 & 4, respectively. Larvae were weighted by
electronic balance. The increment of length was recorded after the 1st days and continued for
PL stage. For measuring length, 30 larvae (15 for each LRT) were sampled for treatment 1, 2,
3 & 4 respectively. Larvae were weighted by gram scale.
Determination of Specific Growth Rate (SGR)
Specific growth rate (SGR) percentage was recorded from 2nd day to PL stage (as feeding
started from 2nd days). Twelve separate % SGR values were recorded for every corresponding
stage of each treatment (T-1, T-2, T-3 & T-4) and finally the overall % SGR value was
determined for the all four treatments. The specific growth rate (SGR) was determined from
the following formula as advocated by Sedgwick (1979).
SGR (% /day) =
100
tlogWologWt
Mean Daily Growth Rate (g/day)
Twelve separate mean daily growth rate values were recorded from 2nd day to PL stage (as
feeding started from 2nd days) for every corresponding stage of each treatment(T-1, T-2, T-3
& T-4) and finally the overall mean daily growth value was determined for the all four
treatments. Mean daily growth rate in terms of length and weight were determined from a
simple mathematical equation as advocated by Sedgwick (1979).
Mean daily growth rate (g /day) =
tWoWt
and
Mean daily growth rate (mm /day) =
tLoLt
;
Where, Wt = Mean body weight (g) at time t, Wo = Mean body weight (g) at time 0, Lt
=Mean body length (mm) at time t, Lo = Mean body length(mm) at time 0,
t =Times in day.
Determination of Metamorphosis of the Larvae
The larval stages of the prawn were observed every day. According to Chowdhury
et.al.(1993), the larvae passes through eleven distinct stages before metamorphosis. At the
first stage it is less than 2 mm in length, from the tip of the rostrum to the end of the telson.
The time taken to complete metamorphosis depends mainly on water temperature and
salinity. Given proper management of both, as well as of the supply of feed, it takes 35-40
days for metamorphosis into post-larvae to be completed. Post-larvae look like small prawn
and move forward. Instead of swimming in the water, they crawl along the wall or bottom of
the tank. Post-larvae harvesting can begin when about half the larvae have metamorphosed.
Evaluation of Hufa Enriched Artemia Nauplii for the Growth, Metamorphosis 137
Determination of Food Conversion Ratio (FCR)
Eight separate food conversion values were recorded from 2nd day to 12th stage or every
corresponding stage of each treatment (T-1, T-2, T-3 & T-4) and finally the overall mean
daily growth rate (g/day) value was determined for the all four treatments. The FCR was
calculated by the following standard formula,
FCR =
gainWeight
consumedFood
.
Determination of Feed Efficiency (FE)
Eight separate feed efficiency values were recorded from 2nd day to 12th stage or every
corresponding stage of each treatment (T-1, T-2, T-3 & T-4) and finally the overall mean
feed efficiency value was determined for the all four treatments. The feed efficiency value
was calculated by the following standard formula:
% FE = (Feed given – Feed consumed) / 100
Determination of the Survival Rate (%)
The survival rate of larvae was affected by many factor, but the result in this trial showed that
the stocking density not only has effect on but also plays and important role in survival rate
of larvae. The larval survival rate estimated twice in daily by using the volumetric method
under strong aeration at morning and evening to get random distribution of larvae. The larval
survival estimation was terminated when post larvae was observed. The final estimation of
post larval survival was done when the larvae was totally were post larvae. All the post larvae
in the tank were removed and counted. Survival rate was calculated by the following equation
(Habib et al., 2014):
Survival rate (%) =
100
stockedlarvaeofnumberTotal populationTotal
Determination of Physio-chemical Parameters
Water temperature was recorded by using a thermometer. The dissolve oxygen (DO) content
of water was determined by Winkler method. Water Salinity was determined by
Refractometer. Water pH was recorded by using a digital pen pH meter. Nitrate-NO2 was
determined by HEKEDO kit (Made in Taiwan). Alkalinity was measured by the following
method APPHA,1976.
Stress Test
A sample of 300 PL were taken from each of 4 treatment tanks, placed into 12 beakers (100
PL into each beaker) with seawater (at the same temperature and salinity as the larval rearing
tank) containing 250 ppm, formalin. After 1 hour the PL that were still active were counted
as percentages.
138 Parvez et al.
Survival rate (%) =
100
beakerinPLofnumberTotal PLactiveofnumberTotal
Statistical Analysis
Statistical analysis was by using SPSS software.
RESULTS
Increment of Length
The length increment of M. rosenbergii larvae were observed in all stages of the study period.
At the time XІІ / PL stage higher mean length (6.935mm) has been recorded in the T-4,
where has used 12 hours HUFA enriched Artemia nauplii and lower means weight
(1.950mm) has been recorded in the T-1 has used un-enriched Artemia nauplii as live feed.
Final weight was significantly higher in T-4 than T-1, T-2 and T-3. This type of result has not
only been found in the XІІ / PL stage but also in every stage. From beginning of rearing until
the 10th day there was no significance different of the length of larvae. The development of
the length of larvae was faster in T-4 than T-1, T-2 and T-3.
Table 3: ‘F’ Value for Four Samples in Terms of Length in Every Corresponding Stage
Stage
Sampling Size
(mm)
Average length (mm)
Value
of [F]
T-1
T-2
T-3
T–4
І
30
1.950**
2.045**
2.060**
2.114**
44.909
ІІ
30
2.145
2.045
2.247
2.115
131.355
ІІІ
30
2.385
2.424
2.449
2.606
49.2299
ІV
30
2.666
2.744
2.816
2.901
70.7621
V
30
2.940
3.028
3.164
3.355
66.7178
VІ
30
3.247
3.287
3.435
3.746
898.833
VІІ
30
3.566
3.585
3.750
4.059
348.893
VІІІ
30
4.542
4.620
4.672
4.696
3.7141
ІX
30
5.486
5.611
5.638
5.970
30.613
X
30
6.149
6.208
6.210
6.461
101.697
XІ
30
6.446
6.560
6.563
6.733
122.432
PL
30
6.737*
6.823**
6.863**
6.935**
53.0201
Different number of star in stage denoted significantly different at the level p<0.092.
Different number of star in stage PL denoted insignificantly different at the level p<0.192.
Increment of Weight
The weight increment of M. rosenbergii larvae was observe of all stages of study period. At
the time XІІ / PL stage higher mean weight (.0057577g) has been recorded in the T-4 where
Evaluation of Hufa Enriched Artemia Nauplii for the Growth, Metamorphosis 139
has used 12 hours HUFA enriched Artemia nauplii and lower means weight (.0001107) has
been recorded in the T-1 has used un-enriched Artemia nauplii as live feed. Final weight was
significantly higher in T-4 than T-1, T-2 and T-3. This type of result has not only been found
in the XІІ / PL stage but also in every stage. From beginning of rearing until the 11th day
there has no significance different of the weight of larvae. The development of the weight of
larvae was faster in T-4 than T-1, T-2 and T-3.
Table 4: F’ Value for Four Samples in Terms of Weight (g) Corresponding Stage
Different number of star in all stage denoted *=insignificantly different at the level of < .145 and **= significantly
at the level p<0.092.
Specific Growth Rate (SGR)
The determination of specific growth rate (SGR) was recorded after ІІ stage/ 2nd days because
the enriched Artemia or feeding trial was started from ІІ stage. Overall specific growth rate
was 5.93%, 6.87%, 7.09% and 8.00% in T-1, T-2, T-3 and T-4, respectively. Higher overall
specific growth rate was in T-4 (5.93%) and lower in T-1 (5.93%) than other treatments.
Daily Mean Growth Rate in Terms of Length (mm/day) and in Terms of Weight (g
/day)
Overall daily mean growth rate in terms of length (mm/day) was higher in T-4 (0.207
mm/day) and lower in T-2(0.170) than other treatments, T-1 (0.179) & T-3 (0.188). Overall
daily mean growth rate in terms of weight (g /day) also was higher in T-4 (4.00E-05 g /day)
and lower in T-1(2.97E-04) than other treatments, T-2 (3.23E-05) & T-3 (3.23E-05).
Stage
Sampling
Size
(mm)
Average weight (g)
Value of [F]
T–1
T–2
T–3
T–4
І
30
.0001107
.0001110
.0001100
.0001087
1.4823E-03*
ІІ
30
.0001563
.0001553
.0001567
.0001587
0.2440E-03*
ІІІ
30
.0002340
.0002343
.0002407
.0002490
4.2594E-03**
ІV
30
.0003043
.0003143
.0003193
.0003507
13.570E-03**
V
30
.0004250
.0004200
.0004180
.0004200
0.7145E-03*
VІ
30
.0006127
.0006967
.0007097
.0007117
60.8748E-03**
VІІ
30
.0011390
.0011497
.0011880
.0012097
6.1016E-02**
VІІІ
30
.0021840
.0022483
.0023017
.0025047
53.1634E-02**
ІX
30
.0032700
.0032897
.0033870
.0034010
44.6039E-02**
X
30
.0039160
.0039743
.0041920
.0043170
0.9753E-02*
XІ
30
.0048547
.0048610
.0049433
.0050610
11.6442E-02**
PL
30
.0056617
.0057183
.0057403
.0057577
35.9315E-02**
140 Parvez et al.
Metamorphosis of the Larvae
The first PL was observed of in T-4 after 19 days, T–3 after 22 days, T–2 after 24 days and
T-1 after 28 days of the rearing of the larvae. All of the larvae turned up into PL after 26 days
in T –4, after 28 days in T-3, after 29 days in T-2 and after 35 days in T-1. Excellent result
has been found in T–4, which enriched 12 hours with HUFA emulsion.
Table 5: Characteristic of Larval Stages of the Freshwater
Prawn of All Four Treatments
Larval
Stages
Prominent Characteristics
Days after hatching
T-1
T-2
T -3
T –4
І
Sessile eyes
1
1
1
ІІ
Stalked eyes
2
2
2
2
ІІІ
Uropods appear
4
4
4
4
ІV
Two dorsal epigastric teeth at the base of
the rostrum
7
7
6
6
V
Telson narrower and elongated
11
9
8
8
VІ
Pleopod buds appear
15
12
11
10
VІІ
Pleopods biramous and bare
18
15
14
13
VІІІ
Pleopods with setae
22
18
17
15
ІX
Endopods of pleopods with appendices
internae
25
20
19
17
X
Three or four dorsal, teeth on rostrum
28
23
22
19
XІ
Teeth on half of upper dorsal margin
31
25
24
22
XІІ
Metamorphosis
Post-larvae(PL)
Teeth on upper and lower margin of
rostrum (also behavioral changes, mainly
in swimming). They are generally
transparent at this stage, and have a
slightly brown-colored chromatophore on
the head.
35
29
28
26
Food Conversion Ratio (FCR)
Food Conversion Ratio was recorded after ІІ stage/ 2nd days because the enriched Artemia or
feeding trial was started from ІІ stage. Food Conversion Ratio was recorded from
1.050
0.157 to 1.050
0.157, 3.246
0.324 to 3.540
0.531, 3.254
0.211 to 15.4
1.052
and 1.041
0.124 to 2.318
0.307 in T-1, Treatment T-2, T-3 and T-4, respectively. Higher
FCR in T-1 (2.11) and lower in T-4 (1.48) than other treatments.
Evaluation of Hufa Enriched Artemia Nauplii for the Growth, Metamorphosis 141
HUFA in Artemia Gut and Fatty Acid
Under microscope it was found that enriched Artemia nauplii gut was containing HUFA
(Highly unsaturated fatty acid) emulsion which, was not found in newly hatched non
enriched nauplii. It was distinct that enrichment was clearly time dependent. Microscopic
picture showed that highest accumulation of HUFA emulsion in the gut was found after 12
hrs of enrichment and very small amount after 3 hrs of enrichment. The percent of
determined total fatty acid was found to be increased in enriched nauplii in comparison to
newly hatched non enriched nauplii. It was also found that total fatty acid was increased in
enriched nauplii in course of time period of enrichment. Total fatty acid was found in newly
hatched non-enriched, and every three (3hrs, 6hrs and 12hrs) durational enriched nauplii were
as 1.875%, 2.0588%, 2.4026% and 2.4533%, respectively.
Survival Rate of the Prawn Larvae
Survival rate in T-4 (50%), T-3 (45%), T-2 (43%) and T-1 (32%).
Table 6: Survival Percentage (%) in 4 Treatments
Larval
Stage
Survival percentage (%) in 4 Treatments
T-1
T-2
T-3
T-4
І
100
100
100
100
ІІ
90
96
96
97
ІІІ
83
90
92
93
ІV
75
85
86
87
V
68
82
83
85
VІ
55
78
80
83
VІІ
51
72
75
78
VІІІ
43
69
72
75
ІX
40
65
68
70
X
38
58
63
65
XІ
36
47
48
60
PL
32
43
45
50
Higher Survival rate has found in T-4 (50%), where as used 12 hours enriched Artemia
nauplii and lower survival rate in T-1 (32%) where as used non-enriched Artemia nauplii.
Water Quality of Larval Rearing Tank
Physio-chemical parameters in LRT (all 4 treatments T-1, T-2, T-3 and T-4) were analyzed
and the parameters were maintained at the suitable level for larvae.
142 Parvez et al.
Table 7: Mean Value of Physico-chemical Parameters in Four Treatments
Parameters
T-1
T-2
T-3
T-4
Temperature(˚C)
28.9
28.6
29.01
28.9
DO (mg/l)
6.4
6.5
6.4
6.5
Salinity (ppt)
12
12
12
12
Water pH
7.8
7.6
7.2
7.3
NO2-N (mg/l)
>.10
>.09
<0.5
<0.6
Alkalinity ppm
125.6
124.5
123
122
DISCUSSION
In the present study, growth performance of prawn larvae fed on HUFA enriched Artemia
nauplii in T-4 showed better performance than the others. The higher mean growth in terms
of weight prawn larvae was significantly higher in others treatment in every larval stages.
The final mean weight of the larvae was 0.0056617 g, 0.0057183 g, 0.0057403 g and
0.0057577g and the final mean length of the larvae was 6.737 mm, 6.8233 mm, 6.8637 mm
and 6.935 mm in T-1, T-2, T-3 and T-4, respectively. These data are in agreement with the
finding of D’ Abramo et al., (2003), who reported that after metamorphosis to post larvae,
the prawn resemble miniature adults, having a total body length of 7-10 mm and weighing
0.006 – 0.009 g. Chowdhury et al., (1993) found that after metamorphosis the larvae
appeared about 7 mm length. Romdhane et al., (1995) reported lengthening the feeding
period of (W-3) HUFA enriched artemia nauplii, give better results in growth
metamorphosis, survival rate and stress resistance.
The overall specific growth rate of prawn larvae was 5.93 %/day, 6.87 %/day, 7.09 %/day
and 8.00 %/day in T-1, T-2, T-3 and T-4, respectively. The higher specific growth rate was
found in T-4 and lower in T-1. Lower growth rate was found due to low temperature. Low
temperature of water resulted decreases metabolic rate, which ultimately reduce the growth
rate. Willis and Berrigan (1977) reared low growth rate of prawn larvae in low temperature.
Overall daily mean growth rate in terms of weight was 2.97 E-04 g/day,3.74 E-05 g/day, 3.23
E-05 g/day and 4.00 E-05 g/day and in terms of length it was 0.179 mm/day, 0.170 mm/day,
0.188 mm/day and 0.207 mm/day in T-1, T-2, T-3 and T-4, respectively. Higher daily mean
growth rate was found in T-4 due to fed with HUFA enriched Artemia (12 hrs).
In the present study, first 5% PL was observed in 28th day, 24th day, 22nd day and 19th day,
and finally all were turned up to PL within 35th day, 29th day, 28th day and 26th day in T-1, T-
2, T-3 and T-4, respectively. Chowdhury et al., (1993) reported that before metamorphosis,
the larvae passes through 11 distinct stages and takes 35 to 50 days. KSU (2002) observed
that to reach the post larval stage, the larvae must undergo 11 molts in approximately 30
days. FAO (2002) found that most of the prawn larvae should have metamorphosed into PL
by 25 to 35 days at the recommended temperature of 28˚C to 31˚C, and it is not usually
economically viable to maintain any batch longer than 32 to 35 days. The result of the present
study was supported by Chowdhury et al., (1993), KSU (2002) and FAO (2002).
Evaluation of Hufa Enriched Artemia Nauplii for the Growth, Metamorphosis 143
The FCR was found 2.11, 1.91, 1.75 and 1.48 in T-1, T-2, T-3 and T-4, respectively. It was
an excellent output of lower FCR in T-4 (1.48), which is an indicator of better food
utilization. Durairaj et al., (1984) found a conversion value ranging from 1.2 – 4.3 for prawn
post larvae. So, the FCR values of all the treatments were satisfactory in respect to this study.
The survival rate of prawn larvae was recorded 32%, 43%, 45% and 50% in T-1, T-2, T-3
and T-4, respectively. Here T-4 showed better survival among others. This might be due to
good water quality of T-4. Chowdhury et al., (1993) reported that larvae stocking 100/L,
keeping all these parameters favorable and by controlling management accordingly, the
survival rate was 30 to 40 PL/L fed on brine shrimp nauplii and custard. FAO (2002)
reported that 40% to 60% survival rate was more normal in practice by using brine shrimp
nauplii (BSN) and egg custard as a larval feed. The present results are newly introduced and
satisfactory in respect of the previous work.
CONCLUSIONS
There are a few research works related to the evaluation of HUFA enriched Artemia nauplii
for growth, survival and metamorphosis of Macrobrachium larvae. This present research is
an effort for first time in Bangladesh. From this study it can be concluded that the enrichment
of Artemia nauplii by HUFA has great effects on Macrobrachium larval production. The
target production of a commercial hatchery could easily be enriched low cost cysts by this
process, would be more economic and tension free larvae production. Moreover, the small-
scale hatcheries can maintain their production cycle in time by getting the fries from their
own controlled larval rearing system.
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