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OPEN
Some biological properties
of spiny eel (Mastacembelus
mastacembelus, Banks & Solander,
1794) living in the Upper Euphrates
River Basin, Turkey
Mehmet Zülfü Çoban1*, Mücahit Eroğlu2 & Mustafa Düşükcan2
This study was carried out to determine some bioecological characteristics of Mastacembelus
mastacembelus, which is the only species of Mastacembelidae family living in Turkey. Fish samples
were caught between 2014–2018 from Keban Dam Lake, one of the most important reservoirs
of the upper Euphrates Basin. In totally, 348 Mastacembelus mastacembelus individuals were
examined, including 178 males and 170 females. The age distributions were defined between the
I–XV age groups. Total lengths ranged from 14.20 to 81.80 cm in males and from 15.60 to 77.30 cm
in females. Total length–weight relationships were calculated as W = 0.0083 × TL2.6516 for males,
W = 0.0043 × TL2.8310 for females and W = 0.0063 × TL2.7256 for all population, and the growth type was
estimated as “negative allometric”. The von Bertalanffy growth parameters for all individuals were
computed as L∞ = 90.99, k = 0.13, t0 = − 0.45. The total (Z), natural (M), fishing (F) mortality rates and
exploitation rate (E) were estimated as Z = 0.313, M = 0.270, F = 0.043 and E = 0.137, respectively. The
length at first capture (Lc) was found as 50.72. The optimum, maximum and economic yields were
calculated as E0.5 = 0.361; Emax = 0.776; E0.1 = 0.664, respectively.
Mastacembelids or spiny eels (Teleostei: Synbranchiformes: Mastacembelidae) are a freshwater fish family. The
family encompassing Mastacembelus (61 species), Macrognathus (24 species) and Sinobdella (1 species) genus
includes 86 species1. However, the Mastacembelidae family is distributed in the Middle East, in Southeast Asia
and north of China, most of its species live in Africa. Members of this family that are anguilliform fishes are
mostly river forms2–5.
The only species of Mastacembelidae family in Turkey is Mastacembelus mastacembelus and is distributed in
Tigris, Euphrates and Asi River systems6,7. The dorsal, caudal, and anal fins of the M. mastacembelus individuals
living in Africa are jointed, but in individuals living in Turkey are not integrated. They live in lotic and lentic
systems where are muddy and sandy grounds which are usually plentiful in vegetation and low in elevation. They
hide in plants or bury in bottom muds to protect themselves during daytime5,8,9.
Some of the morphological features of M. mastacembelus, which is called Mesopotamian spiny eel, are as follows: Dorsal spine 33–35; Anal spine 3–3; Dorsal fin ray 70–78; Anal fin ray 70–78; Caudal fin ray 16–21; Pectoral
fin ray 18–21; Abdominal vertebrae 36–37; Caudal vertebrae 49–51; Total vertebrae 85–88; Lower jaw length
0.7–1.9; Upper jaw length 1.3–3.2; Head depth 3.3–6.1; Body depth 6.7–11.2; Rostral length 1.6–3.1 (Fig. 1)10,11.
Several studies have been carried out on the morphological characteristics5,10,11, embryo development12, digestive system content13, otolith size-fish length14, fish age-otolith size15, reproduction and growth characteristics16–18
of M. mastacembelus throughout Turkey. This study has got importance for being the first scientific research on
the growth parameters of M. mastacembelus distributed in the Keban Reservoir located on the Euphrates River.
Also, no studies were found on the mortality and exploitation rates, the length at first capture (Lc), the length at
recruitment (Lr) and yield per recruit (Y/R) of M. mastacembelus.
1
Keban Vocational Schools, Firat University, Keban, Elazığ, Turkey. 2Faculty of Fisheries, Firat University,
23119 Elazığ, Turkey. *email: mzcoban@firat.edu.tr
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Figure 1. A sample of M. mastacembelus caught during the study (original photo).
Figure 2. The map of Keban Dam Lake [Google Maps: https://www.google.com/maps/@38.8025012,38.91705
08,9z (Accessed 10 February 2021)]21.
Materials and methods
Study area and sample collection. Keban Dam was built between 1965 and 1975 in the Keban district
for electric production and irrigation. It is the second larger artificial lake in Turkey, was built on Euphrates
River in the eastern part of Turkey (within 38° 37′ and 39° 20′N; 38° 15′ and 39° 52′E). The dam lake is 845 m
above the sea level and has 675 km2 surface areas at maximum level, 160 m in maximum depth and 64,100 km2
in basin area (Fig. 2)19,20.
This study was carried out between 2014 and 2018 in Keban Dam Lake. Fish samples were caught using gill
nets with 22, 28, 34, 36, 42, and 55 mm mesh sizes and crayfish fyke-nets, which used prevalently in the region,
with D form and 36 mm stretched mesh size, structured with five hoops and a barrier. Most of the samples were
taken from crayfish fishermen during crayfish hunting periods (December–June)18. Total length (TL, cm) and
weight (W, g) of all fish samples were measured and its sexes were noted according to Lagler et al.22.
Age and growth.
Ages of samples were counted by using vertebrae. Because Gümüş et al. examined various
bony structures in M. mastacembelus and reported that vertebrae are the most suitable structures for age estimation of this species. The vertebrae were immersed in boiling water for approximately 5 min. The vertebrae were
then cleaned with a soft cloth and washed with alcohol. Larger vertebrae samples were processed with decolourant for about 1 min and immersed again with water. The vertebrae were dried at 105 °C for 15 min to increase the
visibility of annular patterns, and they were examined in alcohol using a trinocular microscope (Olympus CX41
microscope and Olympus DP25 monitoring system), magnification of 10 × and 15 ×18.
The sex ratio of the samples was investigated using the Chi-Square test (X2)23. Condition factor (CF) was
determined from CF = (W × 100)/L3 equation24. Length–weight relationships were computed from the Le Cren’s
equation and the investigation of the age-length relationship of the M. mastacembelus, the von Bertalanffy
growth equations (VBGE) were used25. The growth performance of fishes was estimated with Munro’s growth
performance (phi-prime) index (φ′)26. Equations:
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W = a × TLb
Lt = L∞ × 1 − e(−K×(t−t0 ))
b
Wt = W∞ × 1 − e(−K×(t−t0 ))
ϕ ′ = LogK + 2LogL∞
where: Lt: length of the fish at age t; L∞: asymptotic length; K: brody growth coefficient; t0: age of the fish at
0 cm length; Wt: weight of the fish at age t; W∞: asymptotic weight; a and b: constants of the length–weight
relationship25.
The VBGE parameters (L∞, K and t0) and Standard Error’s (SE) were calculated from the age-length data
by using the FAO-ICLARM FiSAT II package27. Length–weight relationships of samples and standard error
(SE) of a and b values were determined with SPSS 21.0 statistical software (SPSS Inc.). The confidence interval
(CI(%95)) values of VBGE parameters (L∞, K and t0) and a and b values in the length–weight relationships were
calculated with CI = SE × t(n−1) equation (tn−1 is the critical value of the theoretical t-distribution for n − 1 degrees
of freedom)25. The differences between the length–weight relationship parameters and VBGE parameters of male
and female individuals were examined by ANCOVA test23.
Mortality. The total mortality rate (Z) was estimated with the linearized catch curve based on age composition data. In this method, a linear regression analysis was performed for x = age, y = ln(N). In this regression,
the slope (b) is accepted as “Z”. The natural mortality coefficient M was calculated by Pauly’s empirical formula
(lnM = − 0.0152–0.279 × ln L∞ + 0.6543 × ln K + 0.4630 × lnT), while the fishing mortality coefficient F was computed by subtracting M from Z (F = Z − M). The exploitation ratio E was calculated by the formula E = F/Z25.
The length at first capture (Lc). The mid-point of the smallest length classes in the catch during the study
period was accepted as the recruitment length (Lr). The length at first capture (Lc) was determined graphically
by the cumulative catch curve analysis according to Pauly24.
The corresponding age at first capture (tc) was calculated as:
Lc
1
t(Lc) = t0 − × LN 1 −
K
L∞
The yield per recruit. The yield per recruit of M. mastacembelus, caught in this study, was calculated using
the following model of Beverton and Holt.
Y
1
3S
3S2
S3
= F × exp [−M × (tc − tr)] × W∞ ×
−
+
−
R
Z
Z+K
Z + 2K
Z + 3K
where: Y/R is the yield per recruit, F is the fishing mortality, M is the natural mortality, tc is the age at first capture,
tr is the age at recruitment, W∞ is the theoretical maximum weight, Z is total mortality, K is growth coefficient
and S equal to following equation: S = e−K×(tc −t0 )25.
The growth type of fishes, the differences between total lengths, weights and condition factors of males and
females were assigned by Student’s t test using SPSS 21.0 Computer Program.
Results
Age and sex distribution. 178 (51.15%) of a total of 348 M. mastacembelus individuals were male and
170 (48.85%) of them are female. It was determined that the ages of investigated individuals ranged between the
I–XV age groups. The overall sex ratio was estimated as 1:1.03 (females/males), this result was not statistically
different from the 1:1 value (X2 = 0.09 < X2(1, 0.05) = 3.84, p > 0.05).
Length and weight distribution. Total length values ranged from 14.20 to 81.80 cm in males and from
15.60 to 77.30 cm in females. Total length measurements of males and females were statistically divergent in
VII, VIII, IX and X age groups (p < 0.05) (Table 1). In the length frequency distribution, the maximum number
of fishes were detected in 59–64 cm length group; with 8.46% (27 individuals) for males and with 7.52% (24
individuals) for females (Fig. 3).
The weight measurements varied from 13.20 to 1131.10 g for males, and from 13.20 to 1010.30 g for females.
According to the t test results, the weight measurements of males and females were not found statistically different in all age groups (p > 0.05) (Table 1).
Length–weight relationships. As a result of the covariance analysis (ANCOVA) applied to the length–
weight relationship of male and female individuals, it was determined that there was no statistically significant
difference between the parameters (ANCOVA: df = 1, F = 0.20, p = 0.651). The “b” value was found to be statistically different from “3” (p < 0.05) both in two sexes and in all population, thereby it was found that the growth
type was “negative allometric” in males, females and all population.
The total length–weight relationships were calculated for male, female, and all population as follows:
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x ± S.h. (min–max)
Male
Age groups
Female
Total length
Weight
N
T test for lengths
T test for weights
Total length
Weight
I
4
17.60 ± 1.60 (14.20–20.80) 15.80 ± 1.77 (13.20–21.00) 2
15.90 ± 0.30 (15.60–16.20)
13.60 ± 0.40 (13.20–14.00) p > 0.05
p > 0.05
II
8
25.58 ± 1.17 (24.00–30.20) 44.72 ± 2.61 (41.00–55.00) 12
25.76 ± 1.36 (19.20–29.70)
46.69 ± 6.48 (25.00–70.10) p > 0.05
p > 0.05
11
114.09 ± 15.80 (58.00–
36.39 ± 2.01 (27.20–45.70)
192.40)
16
86.90 ± 6.90 (51.80–
32.57 ± 0.70 (27.00–38.40)
162.80)
p > 0.05
p > 0.05
IV
18
151.19 ± 16.47 (58.00–
39.58 ± 1.48 (28.70–50.10)
301.90)
24
127.84 ± 16.56 (50.40–
37.09 ± 1.53 (29.10–49.60)
295.50)
p > 0.05
p > 0.05
V
22
46.75 ± 1.17 (41.20–59.60)
251.10 ± 24.42 (150.00–
22
576.30)
45.23 ± 1.81 (31.20–58.40)
241.51 ± 31.57 (64.00–
593.00)
p > 0.05
p > 0.05
VI
25
55.38 ± 1.09 (47.10–65.40)
342.94 ± 19.54 (228.00–
24
584.00)
50.97 ± 2.25 (36.70–64.60)
311.28 ± 32.97 (94.00–
534.00)
p > 0.05
p > 0.05
VII
27
60.83 ± 0.63 (57.10–69.10)
438.79 ± 13.80 (344.50–
31
594.90)
56.14 ± 1.70 (41.80–64.70)
415.55 ± 32.29 (130.70–
608.00)
p < 0.05
p > 0.05
VIII
19
65.41 ± 0.57 (62.40–70.00)
541.04 ± 17.41 (442.00–
14
673.80)
62.11 ± 1.53 (48.10–66.70)
536.51 ± 37.23 (190.30–
632.00)
p < 0.05
p > 0.05
IX
12
637.83 ± 25.39 (502.00–
9
68.78 ± 0.58 (66.50–73.10)
787.40)
583.16 ± 23.90 (484.00–
64.28 ± 1.69 (53.80–68.40)
671.51)
p < 0.05
p > 0.05
X
11
69.72 ± 0.24 (68.10–71.10)
671.22 ± 25.07 (554.00–
5
826.00)
66.14 ± 1.40 (63.00–70.20)
612.09 ± 48.28 (485.00–
760.00)
p < 0.05
p > 0.05
XI
6
72.08 ± 0.49 (69.90–73.00)
641.03 ± 33.71 (553.10–
4
774.00)
69.35 ± 1.81 (64.00–72.00)
732.30 ± 88.91 (488.20–
886.00)
p > 0.05
p > 0.05
XII
6
73.55 ± 0.68 (72.20–76.00)
815.33 ± 50.76 (670.70–
3
982.90)
72.33 ± 0.64 (71.30–73.50)
772.40 ± 8.43 (758.00–
787.20)
p > 0.05
p > 0.05
XIII
4
75.48 ± 1.37 (72.10–78.20)
786.10 ± 94.53 (600.00–
2
980.00)
74.15 ± 1.25 (72.90–75.40)
847.00 ± 39.00 (808.00–
886.00)
p > 0.05
p > 0.05
XIV
3
782.80 ± 97.95 (589.30–
2
76.87 ± 2.07 (72.90–79.90)
906.00)
984.57 ± 25.73 (958.84–
77.05 ± 0.25 (76.80–77.30)
1010.30)
p > 0.05
p > 0.05
XV
2
80.90 ± 0.90 (80.00–81.80)
–
–
III
N
980.60 ± 150.50 (830.10–
–
1131.10)
–
–
Table 1. Total length (cm) and weight (g) values of M. mastacembelus population inhabiting Keban Dam Lake.
Figure 3. The length distribution of M. mastacembelus population inhabiting Keban Dam Lake.
WM = 0.0083 × TL2.6516 R = 0.97, N = 178, CI(%95)b = 0.065, CI(%95)a = 0.002
WF = 0.0043 × TL2.8310 R = 0.97, N = 170, CI(%95)b = 0.076, CI(%95)a = 0.002
WM+F = 0.0063 × TL2.7256 R = 0.97, N = 348, CI(%95)b = 0.051, CI(%95)a = 0.002 (Fig. 4).
Condition factor.
While the condition factor of males ranged from 0.14 to 0.49, in females reached from
0.15 to 0.35. When the mean values were examined, it was determined that the females had a higher condition
than the males and the condition factors decreased with growing age in both sexes, in general (Fig. 5). The difference between the condition factor values of males and females were ascertained statistically different in VI,
VII, VIII, XI and XIV age groups (p < 0.05).
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Figure 4. Length–weight relation of M. mastacembelus population inhabiting Keban Dam Lake.
Figure 5. The of condition factor distributions of M. mastacembelus population inhabiting Keban Dam Lake.
Parameters
Male ± CI(%95)
Female ± CI(%95)
Male + female ± CI(%95)
L∞
88.03 ± 6.17
91.97 ± 6.85
90.99 ± 6.47
K
0.15 ± 0.04
0.12 ± 0.02
0.13 ± 0.02
to
− 0.34 ± 0.45
− 0.53 ± 0.37
− 0.45 ± 0.41
W∞
1189.76
1557.94
1376.49
Ǿ
3.065
3.006
2.997
Table 2. VBGE parameters of M. mastacembelus population inhabiting Keban Dam Lake, according to sexes.
Growth parameters. The von Bertalanffy growth parameters, calculated using age and mean length values, were given in Table 2. It was determined that the differences between measured and estimated (using von
Bertalanffy growth parameters) length and weight values were statistically insignificant in both sexes (p > 0.05).
When the growth curves of both sexes were investigated, it was seen that the males grew faster than the females
in between IV and X age groups, but the difference between in growth rates gradually decreased in the later age
groups, and both sexes grew almost at the same rate (Fig. 6). According to the covariance analysis (ANCOVA),
it was determined that the growth parameters of the sexes were not statistically different (ANCOVA: df = 1,
F = 0.640, p = 0.428).
Mortality and exploitation rates. The natural mortality rate was estimated as M = 0.270 year−1 by using
Pauly’s empirical formula, the total mortality rate was computed as Z = 0.313 year−1 by using the length converted catch curve (Fig. 7) and the fishing mortality rate was calculated as F = 0.043 year−1 by using the formula
F = Z − M. The exploitation rate was computed as 0.137 by using E = F/Z formula. The calculated exploitation rate
value is significantly lower than the optimum exploitation rate value, which is assumed to be 0.50.
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Figure 6. Age-length relations of M. mastacembelus population inhabiting Keban Dam Lake, according to
sexes.
Figure 7. Length converted catch curve.
Figure 8. Cumulative length frequency distribution and the length at first capture of M. mastacembelus
population inhabiting Keban Dam Lake.
Length at first capture (Lc) and recruitment (Lr). The cumulative length-frequency distribution graph
was drawn to determine the length at first capture (Lc) of M. mastacembelus caught between 2014–2018 in
Keban Dam Lake. According to Fig. 8, the length at first capture (Lc) was found to be 50.72 cm, 15.5 cm, which
is the midpoint of the smallest size class, was accepted as the length at recruitment (Lr). The ages corresponding
to Lc and Lr were calculated as tc = 5.82 year and tr = 0.98 year, respectively, using the VBGE parameters.
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Figure 9. Yield per recruit analysis of M. mastacembelus population inhabiting Keban Dam Lake.
Yield per recruit. The relative yield per recruit model (Y/R) was calculated using the knife-edge method of
Beverton and Holt. According to the results, the optimum sustainable yield (E0.5) was found to be 0.278, the maximum sustainable yield (Emax) to be 0.776 and the economic yield (E0.1) to be 0.355 (Fig. 9). It was seen that the
current exploitation rate calculated as 0.137 is lower than the optimum, maximum and economic yield indices.
Discussion
In this study; a total of 348 M. mastacembelus individuals (178 male and 170 female) were examined and the age
distributions were found to vary between 1–15 for males (14.20–81.80 cm) and 1–14 for females (15.60–77.30 cm).
Kılıç, ascertained age distribution 1–7 in males (21.0–70.0 cm) and 1–5 in females (25.0–62.0 cm) from Karakaya Dam Lake and two rivers flowed to it. He also reported larger fish specimens from the dam reservoir28. In
another study conducted in Karakaya Dam Lake, Eroğlu and Şen notified that the age distributions were as 1–9
for males (23.7–80.6 cm) and as 1–8 for females (26.6–68.5 cm)16. On the other hand; Pazira et al., from two rivers
in southern Iran, reported age distributions as 0–6 for both males (9.5–43.2 cm) and females (4.2–42.5 cm)29.
In two studies, executed in Ataturk Dam Lake, the age distributions were stated as 1–18 in males (7.0–82.0 cm)
and as 1–9 in females (29.0–69.0 cm) by Oymak et al.17, and were notified as 1–21 for males (14.4–76.9 cm) and
as 1–9 for females (14.9–57.3 cm) by Gümüş et al.18. In all of the mentioned studies, since the catching methods
of the fish samples are similar (gill nets, fish traps and fishing baskets), it is thought that the differences between
fish sizes are due to the difference in living areas instead of the catching technique. In particular, larger Mesopotamian spiny eels samples were caught from lentic systems. It was thought that the inconsistencies between the
age data of Kılıç’s28 and Eroğlu and Şen’s16 studies and the age data of this study were substantially resulted from
age reading and validating errors (especially in old fishes).
In this study; “b” value in the length–weight relationship was determined as 2.7256 for all population (M:
2.6516, F: 2.8310). It was found that “b” value statistically different from “3” in both sexes and in all population, and growth types were revealed as negative allometric. “b” value was stated as 1.923 for combined sexes by
Kılıç28; as 2.524 in males, as 2.144 in females and as 2.275 in all population by Pazira et al.29; as 2.43 for males
and as 2.95 for females by Oymak et al.17; as 2.996 in males, as 2.792 in females and as 2.835 in all individuals
by Gümüş et al.18. The growth type was reported as isometric only for males in the study of Gümüş et al.18. In
all other studies, the growth type was notified as negative allometric consistently with our study. This finding is
also consistent with the morphological structure of M. mastacembelus.
It was estimated that the condition factor values ranged between 0.14–0.49 in males and 0.15–0.35 in females
and it decreased as age progress. Pazira et al., reported as 0.16–0.39 in males and as 0.16–0.46 in females in two
different rivers in Iran29. Eroğlu and Şen stated that the condition factor values varied from 0.17 to 0.30 for males
and from 0.19 to 0.27 for females in Karakaya Dam Lake16. We think that the differences between the condition
factor values resulted from that Eroğlu and Şen’s16 findings were average values and the samples used in Pazira
et al.’s29 study is only obtained from rivers. Because the condition factor values may vary dependently many factors such as age, fish species, habitat, water flow, nutrient, reproductive activity and sampling time30.
In this study; L∞ values were identified for males, females and all population as 88.03 (K: 0.15 year−1), 91.97
(K: 0.12 year−1) and 90.99 (K: 0.13 year−1), respectively. It is thought that the differences with other studies in
Table 3 are due to disparities in study areas, in age distributions and calculation methods. However, it was determined using the Phi prime test whether the VBGE parameters in the other studies were statistically significant,
and it was found that the findings obtained from this study were not statistically different from the findings of
Pazira et al.29, Oymak et al.17 and Gümüş et al.18 (for males t = − 3.314, df = 2, p > 0.05; for females t = − 0.792,
df = 2, p > 0.05).
Natural mortality rate was calculated as M = 0.270, total mortality rate as Z = 0.313, fishing mortality rate
as F = 0.043 and exploitation rate as E = 0.137. The exploitation rate is lower than the optimum value that is
assumed as 0.50. The optimum, maximum and economic yield indices was calculated as E0.5 = 0.278; Emax = 0.776;
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References
Sexes
L∞
K
to
W∞
Ǿ
Kılıç (2002)
M+F
98.59
0.16
− 1.41
1098.92
3.192
Pazira et al. (2005)
Oymak et al. (2009)
Gümüş et al. (2010)
This study
M
92.3
0.08
− 1.46
–
2.833
F
87.3
0.08
− 1.49
–
2.785
M
99.2
0.10
− 0.12
1619.79
2.993
F
69.2
0.26
− 0.35
777.52
3.095
M
80.0
0.14
− 0.45
1106.83
2.952
F
83.6
0.12
− 0.62
1256.59
2.924
M+F
81.7
0.13
− 0.57
1160.39
2.938
M
88.03
0.15
− 0.34
1189.76
3.065
F
91.97
0.12
− 0.53
1557.94
3.006
M+F
90.99
0.13
− 0.45
1376.49
2.997
Table 3. VBGE parameters of different M. mastacembelus populations.
E0.1 = 0.355, and the current exploitation rate (E = 0.137) was lower than these values. M. mastacembelus is not a
direct target species of fishermen in the region, because its long and thin body structure reduces the success of
catching this species and because of its snake-like appearance, it is a species not preferred by consumers. So it is
expected that the fishing mortality rate and the exploitation rate to be low.
In conclusion, M. mastacembelus that is a long-lived and slow-growing species have a low exploitation rate
and fishing mortality rate in Keban Dam Lake. In the future, it is thought that the stock estimation studies will
be beneficial to learn the economic value of this species.
Received: 21 February 2021; Accepted: 21 May 2021
References
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Author contributions
Sample collection and laboratory work: M.Z.Ç., M.E. and M.D. Article writing and evaluation of data: M.Z.Ç.
and M.E.
Competing interests
The authors declare no competing interests.
Additional information
Correspondence and requests for materials should be addressed to M.Z.Ç.
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