Abstract: Growth of fish population from two sites was significantly different from each other (comparison of b = 2.9 and 2.29 P < 0.001). Condition factor also showed similar trend. Mean value of condition factor for site 1, K = 1.04 and mean condition factor for site 2, K = 0.75. Growth performance was higher in site 1 than fishes of site 2. It is concluded that the conditions for growth of Channa punctata were better at site 1, i.e., Basti Rattan Wali, Multan than at site 2, i.e., Talagang, Chakwal.
Introduction
The term growth signify change in mass and the variables undergoing this change may be length or weight, volume or mass, either organism’s whole body or of its various organs and tissues or it may be related to the body components i.e. organs and tissues. Growth may also be related to change in number of animals in a population (Weatherly and Gill, 1987).
Channa punctata is an important member of fresh water fishes and is commercially useful due to its food value (Mirza, 1975; 1990). This fish prefers to live in waters of muddy streams and they have also adapted to live in stagnant waters (Moyle and Cech, 1998). Channa punctata is a carnivore in habit, prolific breeder, development is rapid, matures in first year and attains maximum length of 30 cm (Talwar and Jhingran, 1991).
In view of its growth potential and popularity among fish consumers, present study was developed with an aim to monitor and compare the growth of Channa punctata in wild conditions selecting two different sites using the technique of mass-length and condition factor parameters as a tool as suggested by Weatherley and Gill (1987). This technique has been applied on a number of fish species by Khan et al. (1991), Salam and Janjua (1991, 1992), Javaid et al. (1992), Salam and Mahmood (1993) and Salam et al. (1993) and reviewed by Wootton (1990, 1998). The objective of the current study was to compare the growth performance of the fish at two sites having different ecological regimes
Materials and Methods
Basti Rattan Wali, Multan District and Talagang, Chakwal District were selected for this study during February to May 2000. The two selected sites were different from each other in such a way that site 1 is located in the plains of southern Punjab which is canal irrigated area, while site 2 is located in Potohar region of northern Punjab which is semi mountainous rain fed area. The fish were selected at random and killed, blotted dry, weighed to the nearest 0.01 g using an electronic digital top-pan balance (Chyo, Japan). Their length was measured to the nearest 0.1 cm on fish measuring board. Condition factor (K) for each fish was calculated using the formula of Weatherly and Gill (1987), Wootton (1990, 1998).
Using computer packages Excel and Minitab statistical analysis was carried out including regression analysis and calculation of correlation coefficient. Calculation of t-test and comparison of slopes were done by Zar (1996).
Results
The relationship between wet body mass (M) and total length (TL) of Channa punctata from two different ecological regimes was exponential (Fig. 1) having the general form:
M = a Lb
When the data was logarithmically transformed, a linear relationship was obtained having the general form:
log M = log a + b log L
The values of the constants (a=intercept and b= slope) and regression parameters are given (Table 1). It was observed that growth of Channa punctata was significantly different at two sites. The growth was significantly higher at Basti Rattan Wali, Multan (b = 2.9) than at Talagang ( b = 2.29). When slope “b” of each site was compared with isometric slope b = 3 (Cube Law), it was observed that the value of b for both sites was lower than b = 3 indicating a negative allometry (Fig. 2).
Condition factor (K) of both sites when correlated with wet body mass (M) or length (TL), it was found to be unaffected by length or weight of both sites. Multiple comparisons showed that condition factor at site 1 was significantly higher than at site 2 (Figs. 3 and 4). It was therefore concluded that Channa punctata at site 1 achieved better condition and its growth performance was comparatively better than at site 2.
Discussion
In fish, weight is considered to be a function of length. According to Wootton (1998), if the fish retains the same shape, its specific gravity remain unchanged during lifetime, than it is growing isometrically and the value of exponent ‘b’ would be exactly 3.0 (Ricker, 1975). A value less than 3.0 shows that the fish become lighter for length, as it grows while an exponent greater than 3.0 indicates that the fish becomes heavier for its length as it increases in size.
In present study, value of b = 2.9 for site 1 and b = 2.29 for site 2 shows that Channa punctata of both sites are growing with negative allometry showing exponentially slow growth. This is also interesting that cube law (b = 3.0) appears to be violated in both sites due to less gain in relative weight. Many species have been reported not to conform to cube relationship as shown here by Channa punctata (Javaid and Akram, 1972; Rafiq, 1992; Salam and Sharif, 1997) (Table 2). The cube law may be held in some cases (Salam and Janjua, 1991; Salam and Davies, 1992; Salam and Khaliq, 1992; Salam et al., 1993).
Most fishes do not conform to the cube law because they change their shape with growth (Martin, 1949) and the exponent ‘b’ may have values significantly lower or higher than 3.0. The value of ‘b’ may vary with feeding (Le Cren, 1951), state of maturity (Frost, 1945), sex (Hile and Jobes, 1940) and furthermore between different populations of a species (Hile, 1936; Jhingran, 1968) indicating the taxonomic differences in small populations which is also evident from the present study.
Condition factor (K) remains constant with increasing body size for Channa punctata from both sites showing that condition factor is not affected at all by increasing body length and mass of fish but the mean value of ‘k’ was comparatively better for site 1 (K = 1.04) than for site 2 (K = 0.75).
| Table 1: | Weight-length relationship of Channa punctata involving wet weight, total length and condition factor: correlation coefficient (r), intercept (a), regression coefficient (b) and standard error of b (SE) |
| ns = non significant * = P < 0,05 *** = P < 0.001 1=Basti Rattan Wali 2= Talagang | |
| Table 2: | Weight-length and condition of various fish species |
| Fig. 1: | The relationship between total length and wet weight of Channa punctata (circles for site 1 and triangles for site 2) |
| Fig. 2: | The relationship between total length and log weight of Channa punctata (symbols as for Fig. 1) |
| Fig. 3: | The relationship between total length and condition factor of Channa punctata (symbols as for Fig. 1) |
| Fig. 4: | The relationship between total length and condition factor of Channa punctata (symbols as for Fig. 1) |
It is therefore concluded that better living conditions led to improve the condition factor of the fish. The results from the present study suggest that the living condition of the site: 1 Basti Rattan Wali Multan were better than Talagang, Chakwal.