Table 1 and Fig 2 present the statistical analysis of various parameters including sample size (number of observed specimens), total length (TL), body weight (BW) and length-weight relationship (LWR) parameters ‘a’ and ‘b’ with 95% confidence intervals, coefficient of determination (r
2) and condition factor for both male and female individuals of
E. vacha and
R. kuturnee. In this study, a total of 1453
E. vacha individuals were examined, comprising 732 males and 721 females. The TL of male
E. vacha ranged from 10 cm to 25 cm, while that of females ranged from 11 cm to 27 cm. The total length (TL) for
E. vacha was reported as 30.0 cm from Bangladesh
(Rahman, 1989) and 37.00 cm from the Ganga River, India
(Tripathi and Gopesh, 2017). Compare to the present study lower lengths were recorded from the Jamuna River, Bangladesh
i.e, 16.95 cm
(Sungai et al., 2013), 25.8 cm in the lower part of the Ganges River
(Hossain et al., 2009) and 21.50 cm in the Gomti River
(Sani et al., 2010). The observed variations in TL can be attributed to geographical location and environmental factors, particularly water temperature and food availability
(Hossain and Ohtomi, 2010). For
R. kuturnee, a total of 1273 individuals were examined, including 644 males and 629 females. The TL of male
R. kuturnee ranged from 7 cm to 18 cm, while that of females ranged from 8 cm to 18.5 cm.
The ‘b’ values estimated and analysis of variance for female, male and pooled sexes of
E. vacha and
R. kuturnee (Table 2 and 3) fell within the expected range of 2.5-3.5 and their no significant difference between both of fish species growth
(Froese, 2006). These values were significantly lower than 3, suggesting a negative allometric growth pattern, which could be attributed to a narrow size range observed in these fish species. The correlation coefficient values (r
2) for the length-weight regression ranged from 0.88 to 0.94. These high positive correlation coefficients indicate a strong relationship between total length and total weight, indicating that as the species’ size increases, so does its weight. Similar negative allometric growth pattern for the combined sexes of
E. vacha in the Padma (lower Ganges River) River, Bangladesh
(Hossain et al., 2006, 2009, 2010). Furthermore, negative allometric growth was reported for the female population from the Jamuna River, Bangladesh
(Hossain et al., 2016) and the Indus River, Pakistan
(Soomro et al., 2007; Sungai et al., 2013). A negative allometric growth pattern was noticed for both male (b=2.83) and female (b=2.78) populations of
E. vacha from the Ganga River in northwestern Bangladesh
(Khatun et al., 2018). Conversely, isometric growth
(Soomro et al., 2007) and positive allometric growth pattern
(Sungai et al., 2013) for male populations of
E. vacha from the Jamuna River, Bangladesh and Indus River, Pakistan, respectively.
The condition factor, which is influenced by both biotic and abiotic environmental factors, serves as a valuable indicator for monitoring feeding intensity, growth rates and fish population
(Oni et al., 1983; Blackwell et al., 2000). Additionally, it can be utilized as an index to assess the overall condition of the aquatic ecosystem in which the fish habitat exists
(Barnham and Baxter, 1998). The condition factor (Kn), close to or equal to 1 indicates a satisfactory fitness level for fish species
(Le Cren, 1951; Jisr et al., 2018). The study revealed that the relative condition factor (Kn) for male, female and pooled sex
E. vacha was found to be 1.09, 1.060 and 1.07 respectively. Similarly, for
R. kuturnee, the Kn values varied between males (1.012) and females (1.12), with a pooled sex ratio Kn value closer to the ideal condition (1.001). These findings indicate that Kn values greater than 1 are associated with good growth conditions, suggesting that these fish thrive in favorable environments. Previous studies for
E. vacha in the Padma River, northwestern Bangladesh, reported that the Kn values ranged from 0.78 to 1.12 for males, 1.0 to 1.29 for females and 0.9 to 1.28 for combined sexes
(Hossain, 2010). Similarly, the relative condition factor for
E. vacha in the Ganga River, northwestern Bangladesh, with a range of 0.7747 to 1.49 for males, 0.39 to 0.6654 for females and 0.7552 to 1.457 for combined sexes
(Khatun et al., 2018).
The observed variations in length-weight relationship (LWR) and condition factors can be attributed to several factors such as sex, gonad ripeness, habitat availability, seasonal effects, level of stomach fullness, fish health, preservation method and variations in the length class under examination
(Sungai et al., 2013). It is important to note that the present study did not take into account any of these influential factors on LWRs and condition factors in the studied fishes
(Ferosekhan et al., 2022; Sarkar et al., 2013).
