Effects of size heterogeneity, feeding/fasting strategy and stocking density modulation on body performance and cannibalism rate of Persian sturgeon (Acipenser persicus) larvae
#effects #size #heterogeneity #strategy #density #modulation #body #performance #cannibalism #rate #persian #sturgeon #acipenser #persicus #larvae
2.1.
Fish
and rearing condition
Five hundred and forty Persian
sturgeon
larvae
were selected in hatched group those which were obtained from a pair male and female breeder at the Shahid Dr. Beheshti Sturgeon
Fish
Restocking and Genetic Conservation Center (Rasht, Guilan, Iran) and transferred to the Dr. Yousefpour Marine Fishes Restocking and Genetic Conservation Center (Siahkal, Guilan, Iran). The present study designed as two separate trials described below. Water quality was recorded daily in both experiments as follows: Temperature: 26 ± 0.6 °C, pH: 7 ± 0.3 and dissolved oxygen: 7.5 ± 0.1 mg L-1. Fish
were fed ad libitum with Artemia nauplii and Daphnia sp. six times per day. The growth
performance
and aggressive behavior were monitored daily.
2.2. Experiment
-A
: Size
and feeding/
fasting trial
The first
experiment containing six treatments
recognized based on size
heterogeneity [large fish
(160 ± 12 mg mean weight
) and small fish
(37 ± 0.0 mg mean weight
)] and feeding/
fasting strategy. Experimental treatments
were designed as: A1 (5 large + 5 small starved fish
); A2 (5 large + 5 small fed fish
); A3 (10 large starved fish
); A4 (10 large fed fish
); A5 (10 small starved fish
) and A6 (10 small fed fish
) in triplicate which is illustrated by details in Figure
1. Totally, 180 fish
were distributed in circular plastic tanks (35 cm
diameter × 10 cm
depth) over a 14-day rearing period.
2.3. Experiment
-
B
: Size
, feeding/
fasting strategy and stocking density
trial
The second
experiment was carried out with emphasizing on stocking densities. Totally, 360 larvae
were distributed in six treatments
as: B1 (10 large + 10 small starved fish
); B2 (10 large + 10 small fed fish
); B3 (20 large starved fish
); B4 (20 large fed fish
); B5 (20 small starved fish
) and B6 (20 small fed fish
) which were distributed in circular plastic tanks (35 cm
diameter × 10 cm
depth) over a 14-day which is shown by details in Figure
1.
2.4. Body performance
and cannibalism
rate
The growth
performance
and survival rate
were measured using the following formula:
Weight
gain (WG, g) = final weight
(Wf) – initial weight
(Wi)
Survival rate
(SR, %) = 100 × [final number of fish
/ initial number of fish
]
Cannibalism
assessment was carried out throughout the 14 days
according to the method of Damme et al. (1989). Larvae
were injured or disappeared by the cannibals and died due to natural causes were assayed daily. Then
, difference in fish
numbers between each count was recorded that leads to estimate cannibalism
rate
, using the following formula:
Cannibalism
rate
(%) = 100 – [survival rate
(%) + natural mortality
(%)]
2.5. Statistical analysis
One-way analysis of variance (ANOVA) followed by Duncan's multiple range tests was used for data analysis after checking the normality of data and homogeneity of variances by Kolmogorov-Smirnov and Levene's tests, respectively. Admittedly, independent samples t-test was used for comparison of experimental groups with different manner. Mean values were considered significantly different at P
< 0.05. All statistical analyses were conducted using SPSS statistical package version 18.0 (SPSS Inc., Chicago, IL, USA).
3. RESULTS
3.1. Growth
performance
In the current study, final weight
in Persian
sturgeon
larvae
were gradually affected by size
heterogeneity, feeding/
fasting strategy (Table 1, experiment
-A
) which are significantly decreased by imposing high stocking density
(Table 1, experiment
-
B
). In both experiments, growth
performance
in fed larvae
had a significant difference compared to the starved ones (P
< 0.05). The size
homogeneity had the positive effects on fed larvae
final weight
in experiment
-A
(A4 and A6 groups) and experiment
-
B
(B4 and B6 groups). The stocking density
remarkably affected final weight
of Persian
sturgeon
larvae
(P
< 0.05).
3.2. Mortality
rate
Figure
2 shows the cumulative mortality
rates of Persian
sturgeon
larvae
at experiment
-A
and experiment
-
B
. According to the results, the mortality
rate
increased significantly in starved fish
maintained in experiment
-A
after 5 (A1; A5) or 7 days
(A3) (Figure2-A
), whereas for experiment
-
B
, it increased from first
day, then
decreased significantly after 8 days
(B2, B4 and B6) in fed fish
(Figure
2-
B
). Over 14 days
, the starved fish
(Figure
2-A
) had an upward trend, while this
issue seems stable by stocking density
effects (Figure
2-
B
). Totally, the results revealed that survivability was higher in experiment
-A
rather than experiment
-
B
.
3.2. Cannibalism
rate
Figure
3 provides cannibalism
rates in experiment
-A
and experiment
-
B
that has been followed and calculated by disappeared or injured larvae
. Obviously, the larvae
those are treated by feeding procedure revealed the lower cannibalism
rates than starved ones either in experiment
-A
(Figure
3-A
) or experiment
-
B
(Figure
3-
B
) (P
< 0.05). Considering our data, the cannibalism
rate
was optimized in order to A2 (small and large fed fish
) over experiment
-A
(Figure
3-A
) and B4 (all large fed fish
) over experiment
-
B
(Figure
3-
B
) by 42.5% and 55% across all treatments
, respectively.Submitted by roosta6787 on
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