International Journal of Aquaculture, 2018, Vol.8, No.16, 121-126
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was measured the length to the end of the scale cover (L) to the nearest mm and the total weight (W) to the
nearest g. After the measurements on site, the fish were returned back alive in the river of their catchment.
Table 1 Average values of the physicochemical parameters in the Iliyna River during the sampling period
Water temperature
9.9°C
Oxygen saturation
85.05%
Conductivity
54.5 µS
pH
8.3
The age of the fish was determined on their scales. The diagonal radius was measured by the use of Dokumator,
Lasergeret (Carl Zeiss, Jena) at magnification 17.5х.
Length and weight at age were back calculated and the received values were used to calculate von Bertalanffy’s
growth parameters (Bertalanffy, 1938): L
t
= L
∞
[1-e
-k(t-to)
] and W
t
= W
∞
[1-e
-k(t-to)
]
n
, where L
∞
(W
∞
) = the
asymptotic length (weight); k = relative growth rate; t
o
= prenatal time (the hypothetic age at which the fish would
have 0 length/weight).
To compare the linear and weight growth rate between the different populations 3 approaches were applied: 1.
The populations were arranged in ascending order of the length of the highest age group. Comparing two
populations of different ages, the length of the highest age group of the youngest population was compared
(Zivkov, 1972; Zivkov et al., 1999); 2. Through ω = parameter (Gallucci and Quin, 1979): ω
L
= L
∞
k; ω
W
= W
∞
k,
where k, L
∞
, и, W
∞
are parameters from the von Bertalanffy’s equation; 3. Through the index of length/weight
growth performance (Pauly, 1979; Munro and Pauly, 1983; Pauly and Munro, 1984): φ’=lgk+2lgL
∞
and
φ’=lgk+2/3lgW
∞
, where L
∞
(W
∞
) and k are parameters from the von Bertalanffy’s equation.
2 Results
2.1 Linear growth
The relation between the fish length (L) and scale radius (R) is described by the equation L=12.067R+1.4829;
r=0.94.
The back calculated average length and length increments are presented in Table 2. Increasing the fish age, the
average annual increments (t) are changing irregularly. The highest length increment occurs during the second
year (6.71 cm) and the smallest during the fifth year (1.96 cm). The increase of the length (L) with the age is well
described by von Bertalanffy’s linear growth equation (Figure 1): L
t
=23.16 [1-e
-0.4666 (t-0.38)
], r=0.995, and SD=6.8.
Table 2 Back calculated values of the length (L, cm) and the length increments (t, cm) in the end of each year
Generation (Year)
Age group
Lengths (L, cm) in the end of each year
Number of fish
1
st
2
nd
3
rd
4
th
5
th
2011
І
6.461
8
2010
ІІ
6.070
14.455
16
2009
ІІІ
5.827
11.137
14.757
5
2008
ІV
7.172
11.826
16.825
19.239
7
2007
V
6.310
8.723
12.343
15.963
20.790
1
Average lengths
6.34
13.05
15.68
18.83
20.79
Average increments, t=L(n)-L(n-1)
6.34
6.71
2.63
3.14
1.96
2.2 Weight growth
The relation between the length (L) and the weight (W) is described from the equation W=0.0162L
2.9444
, r=0.999.
Based on the regression between L and W, the weights and the weight increments were back calculated (Table 3).
The highest was the weight increment during the fourth year = 37.91 g. The increase of the weight (W) with
the age (t) is well described by the equation of von Bertalanffy for the weight growth (Figure 2):
W
t
=160.692[1-e
-0.4978 (t-0.4164)
]
2.94
, r=0.998 and SD=7.15.
