Studies on Age, Growth and Fecundity of Xenocypris
Microlepis in Daoguanhe Reservoir, Hubei Province, China 1111 2Min Liu, Yindong Wang, Bangxi Xiong*, Guangjun Lv, Qiusheng Hu
1. College of Fisheries, Huazhong Agricultural University, Wuhan 430070, Hubei, PR China
2. Daoguanhe Reservoir aquacultural grounds, Wuhan 430425, Hubei, PR China
E-mail: Xingchen932@126.com; email@example.com
A total of 397 samples collected monthly from Daoguanhe Reservoir from September 2007 to August 2008 were used to study the age, growth and fecundity of X.Microlepis. Of which, 115 species at state
?-? were randomly selected from spawning season for fecundity studying. A linear relationship wasfound between body length and radium of of scales. The von Bertalanffy growth formulae were -0.2641(t+0.2524)-0.2641(t+0.7524)3expressed as Lt=36.93.3(1-e),Wt=805.5193(1-e).The inflexion age t=3.4074, i
when the fish was 24.62cm in length and 238.67 in weight. Multi-regressive analyses showed its absolute fecundity and relative fecundity per centimeter were significantly related with body weight and maturing coefficient, and relative fecundity per gram (Fw) only related with maturing coefficient. Keywords: Age; Growth; Fecundity; Xenocypris Microlepis; Daoguanhe Reservoir
Xenocypris Microlepis, belonging to bleeker family, is a medium-sized commercial fish inhabiting in
River and middle and lower levels of water body, and widely distributed in Heilongjiang, Yangtze Zhujiang area of China. With beefy mandible leech, They scrape food on rubble or sludge. In China, most reservoirs were built in valleys and hills. Compared with lake and pond, reservoir had features of great depths, high water exchange rate, good water quality, ample oxygen, and plenty of natural forage resources.It was reported that there were approximately 60% to 80% natural resource in reservoirs were not fully used (Zhang, 1989), while X.Microlepis could best use this resource that other fish rarely
touch.Therefor, being one of the excellent commercial fish, it could not only bring economic efficience,but also clear up water body, having important ecological significance. X.Microlepis is one of the promising freshwater species. There are many reports about its biological characteristic, culture technology, introduction and domestication (Xia et al. 1992; Dai 2001; Li 2001;
Wang et al. 2002; Ren and Ren 2003; Wang et al. 2003; Li et al. 2005; Li et al. 2006; Peng 2007). However, detailed descriptions of its growth and fecundity have not been well documented. Being introduced in 1970s, it has developed steady population in Daoguanhe Reservoir, and made up of 15% of fish production during 1985-1988(Xu et al., 1991). However, production sharply decreased in recent years, with a proportion of less than 10% (not published).
The aim of this work was to study the age, growth and fecundity of X.Microlepis in order to provide
some basic information for successful fishery management, resource conservation and reasonable utilization of X.Microlepis.
2. Materials and methods
2.1 Sampling site
Daoguanhe Reservoir (30?52′N,114?59′E) situated in Wuhan, Hubei province of China(Fig.1), was a 2middle-sized hilly-lake reservoir built in 1968 with a surface area of 108.84km,a total volume of
73 6.37×10m. The depth ranged from 1.90m to 21.00m. It was created for flood control and irrigation,but also contributed to aquiculture and tourism.
Figure. 1 Map of Daoguanhe Reservoir. The arrows indicate three sampling sites along the reservoir, upstream,
middle stream and downstream.
2.2 Sampling regime
Monthly sampling were carried out from September 2007 to August 2008, a total of 397 samples were obtained. Samples were collected using a seine net with a mesh size of 30-40 mm at three stations, upstream, middle stream and downstream along Daoguanhe reservoir. All speciments were measured for total length(TL,cm),standard length(SL,cm), total weight(TW,g),gonad weight (GW), and calculated somatic weight(TW-GW, g). Scales were removed and stored dry for age determination. The length and weight parameters of each fish were recorded with a precision of 1mm and 0.1g. To analyses annual growth of scales and infer its forming time, we use function a=(R-R)/(R-R) to nnn-1
calculate its monthly marginal increment rate. Where R is radius of scales, Rn and Rn-1 are the radius of last ring and the next to the last ring. The back-calculation growth equation is L=a+(L-a)r/R, where nn
Lis the back-calculation body length, a is the intercept of equation, L is the actual body length, rn n
is average radium of each age group, r is the radius of scales. The von Bertalanffy growth equation was used to fit growth characteristic.
115 female species at stage ?-? were randomly selected from fish yield of April and May 2008 for
fecundity study. Maturing coefficient GSI = 100 × gonad weight/somatic weight. 1g of oocytes were removed from the middle and two ends of the left ovary, mixed, then preserved in 5% formalin, and counted under a dissecting microscope. The absolute fecundity of X.Microlepis was recorded as the
number of mature eggs in the ovaries of ripe samples. Relative fecundity (number of eggs per unit weight) was determined as the number of mature oocytes in relation to total weight or total length. Absolute fecundity = egg numbers per 1 gram ovary × ovary weight (g)
Relative fecundity (F/W) = absolute fecundity / total weight (g)
2.3 Date analyses
All the data were analyzed with STATISTICA software. Relationship between its fecundity and body indices imitated with 8 kinds of mathematic expressions were as following:
2 Y=a+bX Y=a+bXY=1/(a+bX) Y=a+b/X X b -bXY=a+bln(X) Y=abY=aXY=k/(1+ae)
3.1 Age and growth
3.1.1 Age structure and distribution of body length and body weight
A total of 397 samples were collected, whose body length and body weight composition could be seen in Table 1.
Table 1 Measured value of the body length and the body weight at various age
Body length，cm！ Body weight，g！ Age Percentage No. of groups (%) sp ecimens Range Mean Range Mean + 059 14.86 12.4-19.2 14.36 27.5-105.4 47.32
+ 1187 47.10 14.9-24.8 19.12 50.5-224.6 113.94
+ 273 18.39 18.2-26.5 22.72 102.3-345.4 188.01
+ 341 10.33 22.0-28.4 25.22 172.7-420.0 260.76
+ 425 6.30 25.2-31.7 28.58 256.4-514.3 377.80
+ 12 3.02 27.4-33.6 30.78 325.6-612.4 476.02 5
3.1.2 Forming time of annual growth ring
A clear feature of mixed density-incision ring could be seen on the scale of X.Microlepis. A ring was
formed by the connection of the density loop in the front and back side and the incision loop in lateral side of scales..
According to the monthly marginal increment rate in Fig. 2, we concluded that the growth ring of
X.Microlepis on scales was formed once a year, from April to June.
0.2 0.0 1 2 3 4 5 6 7 8 9 10 11 12
Figure.2 The marginal growth rate of X. microlepis scale
3.1.3 Relationship between body length and radius of scale
With statistic software, we can fit body length of X.Microlepis with average radius of front, back, upper,
nether area of scales as well as scale length by linear, parabola, logarithmic , exponential and hyperbolic, equation, etc. Results showed that linear relationship was best, indicating there was a linear relationship between growth of body length and radius of front side of scale. Correlation equation was
2L=6.457+6.7514R (n=397, p<0.001,R=0.9506).
3.1.4 Growth back-calculation ++ With the growth back-calculation formula, back-calculation body length of X.Microlepis ageing 1-5
were obtained(Table 2).Result of t-test between back-calculation body length and its actual length was t=0.7304
equation can exactly describe the relationship between scale length and body length.
Table 2 The growth of X. microlepis at various ages
Body length(cm) Body weight(g) age Back-calculated Relative Growth Growth Back-calculate Relative Instantaneous
body length growth rate invariably index d body weight growth rate growth rate
40.60 1 13.77 36.515 0.467 4.286 157.942 0.002596 104.73 2 18.80 0.001841 24.692 0.552 4.149 95.776 205.04 3 23.44 0.001023 13.047 0.429 2.875 45.257 4 26.50 297.83 8.406 0.363 2.139 27.855 0.000673 5 28.73 380.79
3.1.5 Growth index
In order to analyses the growth intensity, we use growth rate and growth index to divide the growth phrases of X.Microlepis(Table 2, Fig.3 to Fig.5). Growth rate and growth acceleration curve of body
+weight had appearant inflexion point, and the front increased rapidly before age 3, then it slowly
+ decreased(Fig.4 and Fig.5). Growth index was also over 4 before reaching age of 3(Table 2). At the
same time, by observeing the gonad of fish at each age group, most of the animals had become
+maturation at the age of 3. So it could be considered as the rapid and steady growth phrase berore and + after age 3. 7 105 39 900 36 800 6 90 33 700 5 75 30 600 dL/dt L(cm) 4 60 dW/dt 27 500 24 400 3 45 L W 21 300 2 30 18 200 1 15 15 100 120 0 00 2 4 6 8 10 12 14 16 18 0 2 4 6 8 10 12 14 16 18 20 20 age age dFigure.3 The growth curve of X. microlepis Figure.4 The growth rate curve of X.
microlepis 0.0 40 -0.3 30 t T 22 22-0.6 20 L/ddL/dt W/d2 2 22 dW/dt -0.9 10 -1.2 0 -1.5 -10 -1.8 -20 0 2 4 6 8 10 12 14 16 18 20 W(g) dW/dt age
Figure.5 The acceleration curve of X. microlepis dL/dt
3.1.6 Relationship between body length and body weight
Data of body length and body weight were obtained by measuring 179 females and 155 males. By
3.0442correlation analyses, correlation function could be expressed as W=0.01384L. Where exponent verged on 3, which showed body weight varies directly with cube body length, so growth of
X.Microlepis.belonged to proportional growth type.
3.1.7 Growth functions
Deal back-calculation body length with least squares method, we got its maximum L=36.9303cm. By ?
simulating von Bertalanffy growth function in STATISTICA software, growth function of body length,
body weight and growth acceleration were as following:
-0.2641(t+0.7524)2Lt=36.9303(1-e) R=0.9989 -0.2641(t+0.7524)3 2Wt=805.5193(1-e)R=0.9989 -0.2641(t+0.7524) dL/dt=9.7533e-0.2641(t+0.7524)-0.2641(t+0.7524)2 dW/dt=638.2129e(1-e)22-0.2641(t+0.7524) dL/dt=-2.5758e22-0.2641(t+0.7524)-0.2641(t+0.7524)-0.2641(t+0.7524) dWdt=168.5520e(1- e)(3e-1)
From the functions above, we got growth coefficient k=0.2641. When academic body length and body 22weight was 0, age t=0.7524a. According to mathematic theory, there was an equation dW/dt=0 at 0
inflexion point, so the inflexion age of X.Microlepis. t=In3/0.2641+t=3.4074, when W=238.6691g, i0
3.2.1 Sample constitute of individual fecundity
There are 4 age groups (Table 3) of 115 species used as fecundity study.
Table 3 Composition of specimens for calculating the number of X. microlepis’ fecundity
Age groups N0.of Body length(cm) Body weight(g)
specimens Range Mean?SD Range Mean?SD，g！
2+ 53 21.1~25.2 23.06?0.873 148.3~264.5 195.44?23.426
3+ 28 23.8~28.4 25.70?0.900 216.7~420.0 273.70?37.203
4+ 22 25.7~30.6 28.14?1.285 262.4~456.8 359.30?50.991
5+ 12 28.4~32.4 30.18?1.236 376.4~562.7 446.67?55.199
3.2.2 Distribution of fecundity 44Range of individual absolute fecundity (F) was 2.8-8.0×10, with an average of 5.7962×10, 87.27% of the total samples. Values for relative fecundity per centimeter (F) and relative fecundity per gram (Fw) L44were 0.1-0.3×10eggs/cm,0.2223×10eggs/cm,89.09% and 150-250 eggs/g, 212 eggs/g,85.48%. Frequence distribution of fecundity could be seen in Fig.6.