3. Results
Data on egg diameter, newly hatched larvae size in length and weight, yolk sac volume and the age at first feeding of Siberian sturgeon larvae obtained from different
females are reported in Table 1. At hatching, there was a positive and significant
Fig. 1. Linear regression equations and relationship between mean egg diameter and size in length and weight, yolk sac volume and first feeding age of larvae at hatching; and between first feeding age and length and
weight of newly hatched Siberian sturgeon larvae.
correlation between egg size, which varied from 2.8 to 4.1 mm in diameter and TL Ž
. Ž
. r s 0.81; P - 0.001; n s 20 , BW r s 0.88; P - 0.001; n s 20 and yolk sac volume
Ž . Ž
. of newly hatched larvae r s 0.92; P s 0.004; n s 20
Fig. 1 . During the endogenous feeding phase, between hatching and 9–11 days post-hatch, cumulative mortality was
Ž .
Ž .
different between different groups of larvae P - 0.05 and was 0.2–3.6 Table 2 . No significant correlation was found between eggs size and survival during the stage of
Ž .
endogenous nutrition P 0.05 . Dead larvae during this period had some severe
morphological malformations such as hydrocele in the abdominal cavity, heart tube left-side bent or without bending, thinning and breaking of yolk sac walls, twisted body
and underdeveloped tail myomeres. Depending on the maternal origin, first feeding in Siberian sturgeon was observed
Ž between 9 and 11 days post-hatch and was correlated with mean egg diameter r s 0.63;
. Ž
P s 0.004; n s 20 , and with newly hatched larvae size in length r s 0.72; P s 0.003; .
Ž . Ž
. n s 20
and weight r s 0.66; P s 0.002; n s 20
Fig. 1 . At the beginning of Ž
exogenous feeding, mortality sharply increased in all experimental rearing troughs Fig. .
2 . Depending on maternal origin, losses represented 2.1–23.5 of the total mortality. During this period, 70–75 of the dead larvae had food in their stomachs. Significant
differences were detected between mortality of larvae obtained from different females Ž
. P - 0.05 . Mortality rates detected during the endogenous feeding phase were not
Ž .
correlated with mortality rates observed during the exogenous feeding period P 0.05 .
Table 2 Ž
. TL and BW of Siberian sturgeon larvae obtained from different females at 20 days after hatching 20 d.p.h.
Survival of these larvae at first feeding and 20 d.p.h. Data are meanS.E. of the two replicates for each Ž
. treatment. Within columns, treatment means followed by different letters are significantly different P - 0.05 .
Ž .
Ž .
TL mm BW mg
Survival Ž
. Ž
. 20 d.p.h.
20 d.p.h. At first feeding
At 20 d.p.h. Female 1
38.33.2 a 322.871.7 a
97.51.3 ab 95.42.6 acd
Female 2 32.83.0 ce
182.453.2 h 99.30.2 ab
81.62.3 bcd Female 3
31.23.7 e 186.063.1 g
98.90.7 ab 81.04.6 bcd
Female 4 31.53.4 e
169.344.2 h 99.50.2 a
93.52.8 ab Female 5
37.73.5 a 297.548.8 ac
97.91.2 ab 92.52.0 abc
Female 6 31.73.6 e
195.961.7 fg 97.61.3 ab
91.01.5 abcd Female 7
38.23.3 a 308.587.5 ab
99.70.1 a 95.21.1 ad
Female 8 31.22.3 e
168.637.5 h 98.10.1 ab
89.10.8 abcd Female 9
30.52.2 e 159.436.0 h
98.71.3 ab 85.16.8 abcd
Female 10 30.52.2 e
176.737.7 h 99.50.5 ab
94.43.5 ab Female 11
31.62.6 e 192.043.8 fgh
98.91.3 ab 92.84.1 abc
Female 12 30.12.5 e
165.328.6 h 98.70.3 ab
92.02.0 abcd Female 13
35.72.3 ac 252.747.6 ce
96.40.4 b 87.84.1 abcd
Female 14 36.12.7 ab
265.963.1 bcd 99.80.3 a
94.31.0 abc Female 15
33.32.5 b 216.060.6 de
97.50.8 ab 74.02.5 bcd
Female 16 31.43.4 e
192.837.1 fg 98.40.6 ab
84.52.7 abcd Female 17
35.52.8 ad 245.360.6 def
99.30.8 ab 95.40.3 ad
Female 18 32.54.6 e
203.246.0 e 99.70.2 a
94.10.1 ab Female 19
36.23.2 ad 240.762.4 deg
99.60.1 a 95.70.1 ad
Female 20 32.90.6 ce
211.457.0 cfg 99.80.1 a
79.41.3 abcd
Fig. 2. Daily numbers of dead Siberian sturgeon larvae obtained from 20 different females. Dotted line represents the period of transition to exogenous feeding. Data are mean numbers per tank and standard
deviation.
Between the onset of the exogenous feeding and 15 days after hatching, many dead Ž
larvae showed signs of cannibalism e.g., damaged pectoral fins, abdominal cavity, .
barbillons andror opercula . Cannibalism was observed among all experimental groups Ž
. 2–5.4 of total losses . After the transition to exogenous feeding, mortality de-
Ž .
creased dramatically Fig. 2 . During this period, some larvae were observed with slight malformations, such as underdeveloped opercula, no joining of the olfactory septum, or
unpigmented eyes; however, these morphological malformations did not seem to affect
Fig. 3. Linear regression equations and relationship between egg diameter and size in length and weight of Ž
. Siberian sturgeon larvae at the end of the study 20 days post-hatch .
Table 3 SGR of Siberian sturgeon larvae obtained from different females during different rearing periods
Ž .
Data are meanS.E. of the two replicates for each treatment. No significant differences P 0.05 were
found between progenies from different females.
y1
Ž .
SGR day From batching
From first to first feeding
feeding to 20 d.p.h. Female 1
9.60.2 14.60.2
Female 2 10.50.1
14.70.1 Female 3
8.71.0 15.01.1
Female 4 9.10.1
13.50.1 Female 5
9.70.4 15.20.4
Female 6 8.40.6
12.70.4 Female 7
9.70.1 15.30.9
Female 8 9.81.1
12.21.7 Female 9
10.80.6 12.41.2
Female 10 10.11.5
13.20.7 Female 11
9.81.4 13.40.7
Female 12 9.40.6
12.80.6 Female 13
10.60.6 13.60.2
Female 14 9.20.4
15.20.5 Female 15
10.10.2 13.10.5
Female 16 10.60.8
12.91.7 Female 17
10.80.3 14.60.2
Female 18 10.30.2
14.00.9 Female 19
9.40.1 15.20.4
Female 20 10.70.1
14.90.1
larval survival. No signs of myxobacteriosis nor columnariosis were observed after first feed administration in any of the experimental groups.
Larval BW ranged from 322.8 to 159.4 mg and TL ranged from 38.3 to 30.1 mm at Ž
. Ž .
the end of the analysed period 20 days after hatching Table 2 . At this age, the effect
of egg size on larval growth was still evident: larval BW and TL were correlated with Ž
. egg diameter r s 0,73; P - 0.001; n s 20; r s 0,67; P s 0.001; n s 20; respectively
Ž .
Fig. 3 . Although there were differences in final BW and TL of larvae from different Ž
. source females P - 0.05 , SGRs were similar among different sources of larvae during
Ž . Ž
. the examined period P 0.05
Table 3 . No correlation was found between egg size Ž
. and SGR for different developmental stages
P 0.05 . No statistically significant Ž
. correlation was found between survival at first feeding and at 20 days post-hatch and
the egg size and yolk sac volume of newly hatched larvae, BW and TL of newly hatched Ž
. larvae and larvae aged 20 days post-hatch P 0.05 .
4. Discussion
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